commit 923c7a3d18753703c175a7b9b143aa775d436576
parent 0ee35f6a25f7318034e2425ae90e3310deb5dd38
Author: Marcello Stanisci <marcello.stanisci@inria.fr>
Date: Wed, 22 Feb 2017 15:03:47 +0100
python tutorial first draft
Diffstat:
5 files changed, 1519 insertions(+), 0 deletions(-)
diff --git a/python/doc/Makefile b/python/doc/Makefile
@@ -0,0 +1,19 @@
+all: tutorial.pdf tutorial.html
+
+tutorial.pdf: arch.pdf tutorial.texi
+ texi2pdf tutorial.texi
+
+tutorial.html: arch.jpg tutorial.texi
+ texi2html tutorial.texi
+
+arch.pdf:
+ cp ../../common/graphics/arch_nobo.pdf .
+
+arch.jpg:
+ cp ../../common/graphics/arch_nobo.jpg .
+
+clean:
+ rm -f arch.jpg arch.pdf tutorial.html tutorial.pdf
+
+info_TEXINFOS = tutorial.texi
+manual_TEXINFOS = version.texi
diff --git a/python/doc/fdl-1.3.texi b/python/doc/fdl-1.3.texi
@@ -0,0 +1,506 @@
+@c The GNU Free Documentation License.
+@center Version 1.3, 3 November 2008
+
+@c This file is intended to be included within another document,
+@c hence no sectioning command or @node.
+
+@display
+Copyright @copyright{} 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
+@uref{http://fsf.org/}
+
+Everyone is permitted to copy and distribute verbatim copies
+of this license document, but changing it is not allowed.
+@end display
+
+@enumerate 0
+@item
+PREAMBLE
+
+The purpose of this License is to make a manual, textbook, or other
+functional and useful document @dfn{free} in the sense of freedom: to
+assure everyone the effective freedom to copy and redistribute it,
+with or without modifying it, either commercially or noncommercially.
+Secondarily, this License preserves for the author and publisher a way
+to get credit for their work, while not being considered responsible
+for modifications made by others.
+
+This License is a kind of ``copyleft'', which means that derivative
+works of the document must themselves be free in the same sense. It
+complements the GNU General Public License, which is a copyleft
+license designed for free software.
+
+We have designed this License in order to use it for manuals for free
+software, because free software needs free documentation: a free
+program should come with manuals providing the same freedoms that the
+software does. But this License is not limited to software manuals;
+it can be used for any textual work, regardless of subject matter or
+whether it is published as a printed book. We recommend this License
+principally for works whose purpose is instruction or reference.
+
+@item
+APPLICABILITY AND DEFINITIONS
+
+This License applies to any manual or other work, in any medium, that
+contains a notice placed by the copyright holder saying it can be
+distributed under the terms of this License. Such a notice grants a
+world-wide, royalty-free license, unlimited in duration, to use that
+work under the conditions stated herein. The ``Document'', below,
+refers to any such manual or work. Any member of the public is a
+licensee, and is addressed as ``you''. You accept the license if you
+copy, modify or distribute the work in a way requiring permission
+under copyright law.
+
+A ``Modified Version'' of the Document means any work containing the
+Document or a portion of it, either copied verbatim, or with
+modifications and/or translated into another language.
+
+A ``Secondary Section'' is a named appendix or a front-matter section
+of the Document that deals exclusively with the relationship of the
+publishers or authors of the Document to the Document's overall
+subject (or to related matters) and contains nothing that could fall
+directly within that overall subject. (Thus, if the Document is in
+part a textbook of mathematics, a Secondary Section may not explain
+any mathematics.) The relationship could be a matter of historical
+connection with the subject or with related matters, or of legal,
+commercial, philosophical, ethical or political position regarding
+them.
+
+The ``Invariant Sections'' are certain Secondary Sections whose titles
+are designated, as being those of Invariant Sections, in the notice
+that says that the Document is released under this License. If a
+section does not fit the above definition of Secondary then it is not
+allowed to be designated as Invariant. The Document may contain zero
+Invariant Sections. If the Document does not identify any Invariant
+Sections then there are none.
+
+The ``Cover Texts'' are certain short passages of text that are listed,
+as Front-Cover Texts or Back-Cover Texts, in the notice that says that
+the Document is released under this License. A Front-Cover Text may
+be at most 5 words, and a Back-Cover Text may be at most 25 words.
+
+A ``Transparent'' copy of the Document means a machine-readable copy,
+represented in a format whose specification is available to the
+general public, that is suitable for revising the document
+straightforwardly with generic text editors or (for images composed of
+pixels) generic paint programs or (for drawings) some widely available
+drawing editor, and that is suitable for input to text formatters or
+for automatic translation to a variety of formats suitable for input
+to text formatters. A copy made in an otherwise Transparent file
+format whose markup, or absence of markup, has been arranged to thwart
+or discourage subsequent modification by readers is not Transparent.
+An image format is not Transparent if used for any substantial amount
+of text. A copy that is not ``Transparent'' is called ``Opaque''.
+
+Examples of suitable formats for Transparent copies include plain
+@sc{ascii} without markup, Texinfo input format, La@TeX{} input
+format, @acronym{SGML} or @acronym{XML} using a publicly available
+@acronym{DTD}, and standard-conforming simple @acronym{HTML},
+PostScript or @acronym{PDF} designed for human modification. Examples
+of transparent image formats include @acronym{PNG}, @acronym{XCF} and
+@acronym{JPG}. Opaque formats include proprietary formats that can be
+read and edited only by proprietary word processors, @acronym{SGML} or
+@acronym{XML} for which the @acronym{DTD} and/or processing tools are
+not generally available, and the machine-generated @acronym{HTML},
+PostScript or @acronym{PDF} produced by some word processors for
+output purposes only.
+
+The ``Title Page'' means, for a printed book, the title page itself,
+plus such following pages as are needed to hold, legibly, the material
+this License requires to appear in the title page. For works in
+formats which do not have any title page as such, ``Title Page'' means
+the text near the most prominent appearance of the work's title,
+preceding the beginning of the body of the text.
+
+The ``publisher'' means any person or entity that distributes copies
+of the Document to the public.
+
+A section ``Entitled XYZ'' means a named subunit of the Document whose
+title either is precisely XYZ or contains XYZ in parentheses following
+text that translates XYZ in another language. (Here XYZ stands for a
+specific section name mentioned below, such as ``Acknowledgements'',
+``Dedications'', ``Endorsements'', or ``History''.) To ``Preserve the Title''
+of such a section when you modify the Document means that it remains a
+section ``Entitled XYZ'' according to this definition.
+
+The Document may include Warranty Disclaimers next to the notice which
+states that this License applies to the Document. These Warranty
+Disclaimers are considered to be included by reference in this
+License, but only as regards disclaiming warranties: any other
+implication that these Warranty Disclaimers may have is void and has
+no effect on the meaning of this License.
+
+@item
+VERBATIM COPYING
+
+You may copy and distribute the Document in any medium, either
+commercially or noncommercially, provided that this License, the
+copyright notices, and the license notice saying this License applies
+to the Document are reproduced in all copies, and that you add no other
+conditions whatsoever to those of this License. You may not use
+technical measures to obstruct or control the reading or further
+copying of the copies you make or distribute. However, you may accept
+compensation in exchange for copies. If you distribute a large enough
+number of copies you must also follow the conditions in section 3.
+
+You may also lend copies, under the same conditions stated above, and
+you may publicly display copies.
+
+@item
+COPYING IN QUANTITY
+
+If you publish printed copies (or copies in media that commonly have
+printed covers) of the Document, numbering more than 100, and the
+Document's license notice requires Cover Texts, you must enclose the
+copies in covers that carry, clearly and legibly, all these Cover
+Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
+the back cover. Both covers must also clearly and legibly identify
+you as the publisher of these copies. The front cover must present
+the full title with all words of the title equally prominent and
+visible. You may add other material on the covers in addition.
+Copying with changes limited to the covers, as long as they preserve
+the title of the Document and satisfy these conditions, can be treated
+as verbatim copying in other respects.
+
+If the required texts for either cover are too voluminous to fit
+legibly, you should put the first ones listed (as many as fit
+reasonably) on the actual cover, and continue the rest onto adjacent
+pages.
+
+If you publish or distribute Opaque copies of the Document numbering
+more than 100, you must either include a machine-readable Transparent
+copy along with each Opaque copy, or state in or with each Opaque copy
+a computer-network location from which the general network-using
+public has access to download using public-standard network protocols
+a complete Transparent copy of the Document, free of added material.
+If you use the latter option, you must take reasonably prudent steps,
+when you begin distribution of Opaque copies in quantity, to ensure
+that this Transparent copy will remain thus accessible at the stated
+location until at least one year after the last time you distribute an
+Opaque copy (directly or through your agents or retailers) of that
+edition to the public.
+
+It is requested, but not required, that you contact the authors of the
+Document well before redistributing any large number of copies, to give
+them a chance to provide you with an updated version of the Document.
+
+@item
+MODIFICATIONS
+
+You may copy and distribute a Modified Version of the Document under
+the conditions of sections 2 and 3 above, provided that you release
+the Modified Version under precisely this License, with the Modified
+Version filling the role of the Document, thus licensing distribution
+and modification of the Modified Version to whoever possesses a copy
+of it. In addition, you must do these things in the Modified Version:
+
+@enumerate A
+@item
+Use in the Title Page (and on the covers, if any) a title distinct
+from that of the Document, and from those of previous versions
+(which should, if there were any, be listed in the History section
+of the Document). You may use the same title as a previous version
+if the original publisher of that version gives permission.
+
+@item
+List on the Title Page, as authors, one or more persons or entities
+responsible for authorship of the modifications in the Modified
+Version, together with at least five of the principal authors of the
+Document (all of its principal authors, if it has fewer than five),
+unless they release you from this requirement.
+
+@item
+State on the Title page the name of the publisher of the
+Modified Version, as the publisher.
+
+@item
+Preserve all the copyright notices of the Document.
+
+@item
+Add an appropriate copyright notice for your modifications
+adjacent to the other copyright notices.
+
+@item
+Include, immediately after the copyright notices, a license notice
+giving the public permission to use the Modified Version under the
+terms of this License, in the form shown in the Addendum below.
+
+@item
+Preserve in that license notice the full lists of Invariant Sections
+and required Cover Texts given in the Document's license notice.
+
+@item
+Include an unaltered copy of this License.
+
+@item
+Preserve the section Entitled ``History'', Preserve its Title, and add
+to it an item stating at least the title, year, new authors, and
+publisher of the Modified Version as given on the Title Page. If
+there is no section Entitled ``History'' in the Document, create one
+stating the title, year, authors, and publisher of the Document as
+given on its Title Page, then add an item describing the Modified
+Version as stated in the previous sentence.
+
+@item
+Preserve the network location, if any, given in the Document for
+public access to a Transparent copy of the Document, and likewise
+the network locations given in the Document for previous versions
+it was based on. These may be placed in the ``History'' section.
+You may omit a network location for a work that was published at
+least four years before the Document itself, or if the original
+publisher of the version it refers to gives permission.
+
+@item
+For any section Entitled ``Acknowledgements'' or ``Dedications'', Preserve
+the Title of the section, and preserve in the section all the
+substance and tone of each of the contributor acknowledgements and/or
+dedications given therein.
+
+@item
+Preserve all the Invariant Sections of the Document,
+unaltered in their text and in their titles. Section numbers
+or the equivalent are not considered part of the section titles.
+
+@item
+Delete any section Entitled ``Endorsements''. Such a section
+may not be included in the Modified Version.
+
+@item
+Do not retitle any existing section to be Entitled ``Endorsements'' or
+to conflict in title with any Invariant Section.
+
+@item
+Preserve any Warranty Disclaimers.
+@end enumerate
+
+If the Modified Version includes new front-matter sections or
+appendices that qualify as Secondary Sections and contain no material
+copied from the Document, you may at your option designate some or all
+of these sections as invariant. To do this, add their titles to the
+list of Invariant Sections in the Modified Version's license notice.
+These titles must be distinct from any other section titles.
+
+You may add a section Entitled ``Endorsements'', provided it contains
+nothing but endorsements of your Modified Version by various
+parties---for example, statements of peer review or that the text has
+been approved by an organization as the authoritative definition of a
+standard.
+
+You may add a passage of up to five words as a Front-Cover Text, and a
+passage of up to 25 words as a Back-Cover Text, to the end of the list
+of Cover Texts in the Modified Version. Only one passage of
+Front-Cover Text and one of Back-Cover Text may be added by (or
+through arrangements made by) any one entity. If the Document already
+includes a cover text for the same cover, previously added by you or
+by arrangement made by the same entity you are acting on behalf of,
+you may not add another; but you may replace the old one, on explicit
+permission from the previous publisher that added the old one.
+
+The author(s) and publisher(s) of the Document do not by this License
+give permission to use their names for publicity for or to assert or
+imply endorsement of any Modified Version.
+
+@item
+COMBINING DOCUMENTS
+
+You may combine the Document with other documents released under this
+License, under the terms defined in section 4 above for modified
+versions, provided that you include in the combination all of the
+Invariant Sections of all of the original documents, unmodified, and
+list them all as Invariant Sections of your combined work in its
+license notice, and that you preserve all their Warranty Disclaimers.
+
+The combined work need only contain one copy of this License, and
+multiple identical Invariant Sections may be replaced with a single
+copy. If there are multiple Invariant Sections with the same name but
+different contents, make the title of each such section unique by
+adding at the end of it, in parentheses, the name of the original
+author or publisher of that section if known, or else a unique number.
+Make the same adjustment to the section titles in the list of
+Invariant Sections in the license notice of the combined work.
+
+In the combination, you must combine any sections Entitled ``History''
+in the various original documents, forming one section Entitled
+``History''; likewise combine any sections Entitled ``Acknowledgements'',
+and any sections Entitled ``Dedications''. You must delete all
+sections Entitled ``Endorsements.''
+
+@item
+COLLECTIONS OF DOCUMENTS
+
+You may make a collection consisting of the Document and other documents
+released under this License, and replace the individual copies of this
+License in the various documents with a single copy that is included in
+the collection, provided that you follow the rules of this License for
+verbatim copying of each of the documents in all other respects.
+
+You may extract a single document from such a collection, and distribute
+it individually under this License, provided you insert a copy of this
+License into the extracted document, and follow this License in all
+other respects regarding verbatim copying of that document.
+
+@item
+AGGREGATION WITH INDEPENDENT WORKS
+
+A compilation of the Document or its derivatives with other separate
+and independent documents or works, in or on a volume of a storage or
+distribution medium, is called an ``aggregate'' if the copyright
+resulting from the compilation is not used to limit the legal rights
+of the compilation's users beyond what the individual works permit.
+When the Document is included in an aggregate, this License does not
+apply to the other works in the aggregate which are not themselves
+derivative works of the Document.
+
+If the Cover Text requirement of section 3 is applicable to these
+copies of the Document, then if the Document is less than one half of
+the entire aggregate, the Document's Cover Texts may be placed on
+covers that bracket the Document within the aggregate, or the
+electronic equivalent of covers if the Document is in electronic form.
+Otherwise they must appear on printed covers that bracket the whole
+aggregate.
+
+@item
+TRANSLATION
+
+Translation is considered a kind of modification, so you may
+distribute translations of the Document under the terms of section 4.
+Replacing Invariant Sections with translations requires special
+permission from their copyright holders, but you may include
+translations of some or all Invariant Sections in addition to the
+original versions of these Invariant Sections. You may include a
+translation of this License, and all the license notices in the
+Document, and any Warranty Disclaimers, provided that you also include
+the original English version of this License and the original versions
+of those notices and disclaimers. In case of a disagreement between
+the translation and the original version of this License or a notice
+or disclaimer, the original version will prevail.
+
+If a section in the Document is Entitled ``Acknowledgements'',
+``Dedications'', or ``History'', the requirement (section 4) to Preserve
+its Title (section 1) will typically require changing the actual
+title.
+
+@item
+TERMINATION
+
+You may not copy, modify, sublicense, or distribute the Document
+except as expressly provided under this License. Any attempt
+otherwise to copy, modify, sublicense, or distribute it is void, and
+will automatically terminate your rights under this License.
+
+However, if you cease all violation of this License, then your license
+from a particular copyright holder is reinstated (a) provisionally,
+unless and until the copyright holder explicitly and finally
+terminates your license, and (b) permanently, if the copyright holder
+fails to notify you of the violation by some reasonable means prior to
+60 days after the cessation.
+
+Moreover, your license from a particular copyright holder is
+reinstated permanently if the copyright holder notifies you of the
+violation by some reasonable means, this is the first time you have
+received notice of violation of this License (for any work) from that
+copyright holder, and you cure the violation prior to 30 days after
+your receipt of the notice.
+
+Termination of your rights under this section does not terminate the
+licenses of parties who have received copies or rights from you under
+this License. If your rights have been terminated and not permanently
+reinstated, receipt of a copy of some or all of the same material does
+not give you any rights to use it.
+
+@item
+FUTURE REVISIONS OF THIS LICENSE
+
+The Free Software Foundation may publish new, revised versions
+of the GNU Free Documentation License from time to time. Such new
+versions will be similar in spirit to the present version, but may
+differ in detail to address new problems or concerns. See
+@uref{http://www.gnu.org/copyleft/}.
+
+Each version of the License is given a distinguishing version number.
+If the Document specifies that a particular numbered version of this
+License ``or any later version'' applies to it, you have the option of
+following the terms and conditions either of that specified version or
+of any later version that has been published (not as a draft) by the
+Free Software Foundation. If the Document does not specify a version
+number of this License, you may choose any version ever published (not
+as a draft) by the Free Software Foundation. If the Document
+specifies that a proxy can decide which future versions of this
+License can be used, that proxy's public statement of acceptance of a
+version permanently authorizes you to choose that version for the
+Document.
+
+@item
+RELICENSING
+
+``Massive Multiauthor Collaboration Site'' (or ``MMC Site'') means any
+World Wide Web server that publishes copyrightable works and also
+provides prominent facilities for anybody to edit those works. A
+public wiki that anybody can edit is an example of such a server. A
+``Massive Multiauthor Collaboration'' (or ``MMC'') contained in the
+site means any set of copyrightable works thus published on the MMC
+site.
+
+``CC-BY-SA'' means the Creative Commons Attribution-Share Alike 3.0
+license published by Creative Commons Corporation, a not-for-profit
+corporation with a principal place of business in San Francisco,
+California, as well as future copyleft versions of that license
+published by that same organization.
+
+``Incorporate'' means to publish or republish a Document, in whole or
+in part, as part of another Document.
+
+An MMC is ``eligible for relicensing'' if it is licensed under this
+License, and if all works that were first published under this License
+somewhere other than this MMC, and subsequently incorporated in whole
+or in part into the MMC, (1) had no cover texts or invariant sections,
+and (2) were thus incorporated prior to November 1, 2008.
+
+The operator of an MMC Site may republish an MMC contained in the site
+under CC-BY-SA on the same site at any time before August 1, 2009,
+provided the MMC is eligible for relicensing.
+
+@end enumerate
+
+@page
+@heading ADDENDUM: How to use this License for your documents
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and
+license notices just after the title page:
+
+@smallexample
+@group
+ Copyright (C) @var{year} @var{your name}.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.3
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
+ Texts. A copy of the license is included in the section entitled ``GNU
+ Free Documentation License''.
+@end group
+@end smallexample
+
+If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
+replace the ``with@dots{}Texts.'' line with this:
+
+@smallexample
+@group
+ with the Invariant Sections being @var{list their titles}, with
+ the Front-Cover Texts being @var{list}, and with the Back-Cover Texts
+ being @var{list}.
+@end group
+@end smallexample
+
+If you have Invariant Sections without Cover Texts, or some other
+combination of the three, merge those two alternatives to suit the
+situation.
+
+If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of
+free software license, such as the GNU General Public License,
+to permit their use in free software.
+
+@c Local Variables:
+@c ispell-local-pdict: "ispell-dict"
+@c End:
+
diff --git a/python/doc/lgpl.texi b/python/doc/lgpl.texi
@@ -0,0 +1,549 @@
+@c The GNU Lesser General Public License.
+@center Version 2.1, February 1999
+
+@c This file is intended to be included within another document,
+@c hence no sectioning command or @node.
+
+@display
+Copyright @copyright{} 1991, 1999 Free Software Foundation, Inc.
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+
+Everyone is permitted to copy and distribute verbatim copies
+of this license document, but changing it is not allowed.
+
+[This is the first released version of the Lesser GPL. It also counts
+as the successor of the GNU Library Public License, version 2, hence the
+version number 2.1.]
+@end display
+
+@subheading Preamble
+
+ The licenses for most software are designed to take away your
+freedom to share and change it. By contrast, the GNU General Public
+Licenses are intended to guarantee your freedom to share and change
+free software---to make sure the software is free for all its users.
+
+ This license, the Lesser General Public License, applies to some
+specially designated software---typically libraries---of the Free
+Software Foundation and other authors who decide to use it. You can use
+it too, but we suggest you first think carefully about whether this
+license or the ordinary General Public License is the better strategy to
+use in any particular case, based on the explanations below.
+
+ When we speak of free software, we are referring to freedom of use,
+not price. Our General Public Licenses are designed to make sure that
+you have the freedom to distribute copies of free software (and charge
+for this service if you wish); that you receive source code or can get
+it if you want it; that you can change the software and use pieces of it
+in new free programs; and that you are informed that you can do these
+things.
+
+ To protect your rights, we need to make restrictions that forbid
+distributors to deny you these rights or to ask you to surrender these
+rights. These restrictions translate to certain responsibilities for
+you if you distribute copies of the library or if you modify it.
+
+ For example, if you distribute copies of the library, whether gratis
+or for a fee, you must give the recipients all the rights that we gave
+you. You must make sure that they, too, receive or can get the source
+code. If you link other code with the library, you must provide
+complete object files to the recipients, so that they can relink them
+with the library after making changes to the library and recompiling
+it. And you must show them these terms so they know their rights.
+
+ We protect your rights with a two-step method: (1) we copyright the
+library, and (2) we offer you this license, which gives you legal
+permission to copy, distribute and/or modify the library.
+
+ To protect each distributor, we want to make it very clear that
+there is no warranty for the free library. Also, if the library is
+modified by someone else and passed on, the recipients should know
+that what they have is not the original version, so that the original
+author's reputation will not be affected by problems that might be
+introduced by others.
+
+ Finally, software patents pose a constant threat to the existence of
+any free program. We wish to make sure that a company cannot
+effectively restrict the users of a free program by obtaining a
+restrictive license from a patent holder. Therefore, we insist that
+any patent license obtained for a version of the library must be
+consistent with the full freedom of use specified in this license.
+
+ Most GNU software, including some libraries, is covered by the
+ordinary GNU General Public License. This license, the GNU Lesser
+General Public License, applies to certain designated libraries, and
+is quite different from the ordinary General Public License. We use
+this license for certain libraries in order to permit linking those
+libraries into non-free programs.
+
+ When a program is linked with a library, whether statically or using
+a shared library, the combination of the two is legally speaking a
+combined work, a derivative of the original library. The ordinary
+General Public License therefore permits such linking only if the
+entire combination fits its criteria of freedom. The Lesser General
+Public License permits more lax criteria for linking other code with
+the library.
+
+ We call this license the @dfn{Lesser} General Public License because it
+does @emph{Less} to protect the user's freedom than the ordinary General
+Public License. It also provides other free software developers Less
+of an advantage over competing non-free programs. These disadvantages
+are the reason we use the ordinary General Public License for many
+libraries. However, the Lesser license provides advantages in certain
+special circumstances.
+
+ For example, on rare occasions, there may be a special need to
+encourage the widest possible use of a certain library, so that it becomes
+a de-facto standard. To achieve this, non-free programs must be
+allowed to use the library. A more frequent case is that a free
+library does the same job as widely used non-free libraries. In this
+case, there is little to gain by limiting the free library to free
+software only, so we use the Lesser General Public License.
+
+ In other cases, permission to use a particular library in non-free
+programs enables a greater number of people to use a large body of
+free software. For example, permission to use the GNU C Library in
+non-free programs enables many more people to use the whole GNU
+operating system, as well as its variant, the GNU/Linux operating
+system.
+
+ Although the Lesser General Public License is Less protective of the
+users' freedom, it does ensure that the user of a program that is
+linked with the Library has the freedom and the wherewithal to run
+that program using a modified version of the Library.
+
+ The precise terms and conditions for copying, distribution and
+modification follow. Pay close attention to the difference between a
+``work based on the library'' and a ``work that uses the library''. The
+former contains code derived from the library, whereas the latter must
+be combined with the library in order to run.
+
+@subheading TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+@enumerate 0
+@item
+This License Agreement applies to any software library or other program
+which contains a notice placed by the copyright holder or other
+authorized party saying it may be distributed under the terms of this
+Lesser General Public License (also called ``this License''). Each
+licensee is addressed as ``you''.
+
+ A ``library'' means a collection of software functions and/or data
+prepared so as to be conveniently linked with application programs
+(which use some of those functions and data) to form executables.
+
+ The ``Library'', below, refers to any such software library or work
+which has been distributed under these terms. A ``work based on the
+Library'' means either the Library or any derivative work under
+copyright law: that is to say, a work containing the Library or a
+portion of it, either verbatim or with modifications and/or translated
+straightforwardly into another language. (Hereinafter, translation is
+included without limitation in the term ``modification''.)
+
+ ``Source code'' for a work means the preferred form of the work for
+making modifications to it. For a library, complete source code means
+all the source code for all modules it contains, plus any associated
+interface definition files, plus the scripts used to control compilation
+and installation of the library.
+
+ Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope. The act of
+running a program using the Library is not restricted, and output from
+such a program is covered only if its contents constitute a work based
+on the Library (independent of the use of the Library in a tool for
+writing it). Whether that is true depends on what the Library does
+and what the program that uses the Library does.
+
+@item
+You may copy and distribute verbatim copies of the Library's
+complete source code as you receive it, in any medium, provided that
+you conspicuously and appropriately publish on each copy an
+appropriate copyright notice and disclaimer of warranty; keep intact
+all the notices that refer to this License and to the absence of any
+warranty; and distribute a copy of this License along with the
+Library.
+
+ You may charge a fee for the physical act of transferring a copy,
+and you may at your option offer warranty protection in exchange for a
+fee.
+
+@item
+You may modify your copy or copies of the Library or any portion
+of it, thus forming a work based on the Library, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+@enumerate a
+@item
+The modified work must itself be a software library.
+
+@item
+You must cause the files modified to carry prominent notices
+stating that you changed the files and the date of any change.
+
+@item
+You must cause the whole of the work to be licensed at no
+charge to all third parties under the terms of this License.
+
+@item
+If a facility in the modified Library refers to a function or a
+table of data to be supplied by an application program that uses
+the facility, other than as an argument passed when the facility
+is invoked, then you must make a good faith effort to ensure that,
+in the event an application does not supply such function or
+table, the facility still operates, and performs whatever part of
+its purpose remains meaningful.
+
+(For example, a function in a library to compute square roots has
+a purpose that is entirely well-defined independent of the
+application. Therefore, Subsection 2d requires that any
+application-supplied function or table used by this function must
+be optional: if the application does not supply it, the square
+root function must still compute square roots.)
+@end enumerate
+
+These requirements apply to the modified work as a whole. If
+identifiable sections of that work are not derived from the Library,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works. But when you
+distribute the same sections as part of a whole which is a work based
+on the Library, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote
+it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Library.
+
+In addition, mere aggregation of another work not based on the Library
+with the Library (or with a work based on the Library) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+@item
+You may opt to apply the terms of the ordinary GNU General Public
+License instead of this License to a given copy of the Library. To do
+this, you must alter all the notices that refer to this License, so
+that they refer to the ordinary GNU General Public License, version 2,
+instead of to this License. (If a newer version than version 2 of the
+ordinary GNU General Public License has appeared, then you can specify
+that version instead if you wish.) Do not make any other change in
+these notices.
+
+ Once this change is made in a given copy, it is irreversible for
+that copy, so the ordinary GNU General Public License applies to all
+subsequent copies and derivative works made from that copy.
+
+ This option is useful when you wish to copy part of the code of
+the Library into a program that is not a library.
+
+@item
+You may copy and distribute the Library (or a portion or
+derivative of it, under Section 2) in object code or executable form
+under the terms of Sections 1 and 2 above provided that you accompany
+it with the complete corresponding machine-readable source code, which
+must be distributed under the terms of Sections 1 and 2 above on a
+medium customarily used for software interchange.
+
+ If distribution of object code is made by offering access to copy
+from a designated place, then offering equivalent access to copy the
+source code from the same place satisfies the requirement to
+distribute the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+@item
+A program that contains no derivative of any portion of the
+Library, but is designed to work with the Library by being compiled or
+linked with it, is called a ``work that uses the Library''. Such a
+work, in isolation, is not a derivative work of the Library, and
+therefore falls outside the scope of this License.
+
+ However, linking a ``work that uses the Library'' with the Library
+creates an executable that is a derivative of the Library (because it
+contains portions of the Library), rather than a ``work that uses the
+library''. The executable is therefore covered by this License.
+Section 6 states terms for distribution of such executables.
+
+ When a ``work that uses the Library'' uses material from a header file
+that is part of the Library, the object code for the work may be a
+derivative work of the Library even though the source code is not.
+Whether this is true is especially significant if the work can be
+linked without the Library, or if the work is itself a library. The
+threshold for this to be true is not precisely defined by law.
+
+ If such an object file uses only numerical parameters, data
+structure layouts and accessors, and small macros and small inline
+functions (ten lines or less in length), then the use of the object
+file is unrestricted, regardless of whether it is legally a derivative
+work. (Executables containing this object code plus portions of the
+Library will still fall under Section 6.)
+
+ Otherwise, if the work is a derivative of the Library, you may
+distribute the object code for the work under the terms of Section 6.
+Any executables containing that work also fall under Section 6,
+whether or not they are linked directly with the Library itself.
+
+@item
+As an exception to the Sections above, you may also combine or
+link a ``work that uses the Library'' with the Library to produce a
+work containing portions of the Library, and distribute that work
+under terms of your choice, provided that the terms permit
+modification of the work for the customer's own use and reverse
+engineering for debugging such modifications.
+
+ You must give prominent notice with each copy of the work that the
+Library is used in it and that the Library and its use are covered by
+this License. You must supply a copy of this License. If the work
+during execution displays copyright notices, you must include the
+copyright notice for the Library among them, as well as a reference
+directing the user to the copy of this License. Also, you must do one
+of these things:
+
+@enumerate a
+@item
+Accompany the work with the complete corresponding
+machine-readable source code for the Library including whatever
+changes were used in the work (which must be distributed under
+Sections 1 and 2 above); and, if the work is an executable linked
+with the Library, with the complete machine-readable ``work that
+uses the Library'', as object code and/or source code, so that the
+user can modify the Library and then relink to produce a modified
+executable containing the modified Library. (It is understood
+that the user who changes the contents of definitions files in the
+Library will not necessarily be able to recompile the application
+to use the modified definitions.)
+
+@item
+Use a suitable shared library mechanism for linking with the Library. A
+suitable mechanism is one that (1) uses at run time a copy of the
+library already present on the user's computer system, rather than
+copying library functions into the executable, and (2) will operate
+properly with a modified version of the library, if the user installs
+one, as long as the modified version is interface-compatible with the
+version that the work was made with.
+
+@item
+Accompany the work with a written offer, valid for at
+least three years, to give the same user the materials
+specified in Subsection 6a, above, for a charge no more
+than the cost of performing this distribution.
+
+@item
+If distribution of the work is made by offering access to copy
+from a designated place, offer equivalent access to copy the above
+specified materials from the same place.
+
+@item
+Verify that the user has already received a copy of these
+materials or that you have already sent this user a copy.
+@end enumerate
+
+ For an executable, the required form of the ``work that uses the
+Library'' must include any data and utility programs needed for
+reproducing the executable from it. However, as a special exception,
+the materials to be distributed need not include anything that is
+normally distributed (in either source or binary form) with the major
+components (compiler, kernel, and so on) of the operating system on
+which the executable runs, unless that component itself accompanies the
+executable.
+
+ It may happen that this requirement contradicts the license
+restrictions of other proprietary libraries that do not normally
+accompany the operating system. Such a contradiction means you cannot
+use both them and the Library together in an executable that you
+distribute.
+
+@item
+You may place library facilities that are a work based on the
+Library side-by-side in a single library together with other library
+facilities not covered by this License, and distribute such a combined
+library, provided that the separate distribution of the work based on
+the Library and of the other library facilities is otherwise
+permitted, and provided that you do these two things:
+
+@enumerate a
+@item
+Accompany the combined library with a copy of the same work
+based on the Library, uncombined with any other library
+facilities. This must be distributed under the terms of the
+Sections above.
+
+@item
+Give prominent notice with the combined library of the fact
+that part of it is a work based on the Library, and explaining
+where to find the accompanying uncombined form of the same work.
+@end enumerate
+
+@item
+You may not copy, modify, sublicense, link with, or distribute
+the Library except as expressly provided under this License. Any
+attempt otherwise to copy, modify, sublicense, link with, or
+distribute the Library is void, and will automatically terminate your
+rights under this License. However, parties who have received copies,
+or rights, from you under this License will not have their licenses
+terminated so long as such parties remain in full compliance.
+
+@item
+You are not required to accept this License, since you have not
+signed it. However, nothing else grants you permission to modify or
+distribute the Library or its derivative works. These actions are
+prohibited by law if you do not accept this License. Therefore, by
+modifying or distributing the Library (or any work based on the
+Library), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Library or works based on it.
+
+@item
+Each time you redistribute the Library (or any work based on the
+Library), the recipient automatically receives a license from the
+original licensor to copy, distribute, link with or modify the Library
+subject to these terms and conditions. You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties with
+this License.
+
+@item
+If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License. If you cannot
+distribute so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you
+may not distribute the Library at all. For example, if a patent
+license would not permit royalty-free redistribution of the Library by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Library.
+
+If any portion of this section is held invalid or unenforceable under any
+particular circumstance, the balance of the section is intended to apply,
+and the section as a whole is intended to apply in other circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system which is
+implemented by public license practices. Many people have made
+generous contributions to the wide range of software distributed
+through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing
+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+@item
+If the distribution and/or use of the Library is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Library under this License may add
+an explicit geographical distribution limitation excluding those countries,
+so that distribution is permitted only in or among countries not thus
+excluded. In such case, this License incorporates the limitation as if
+written in the body of this License.
+
+@item
+The Free Software Foundation may publish revised and/or new
+versions of the Lesser General Public License from time to time.
+Such new versions will be similar in spirit to the present version,
+but may differ in detail to address new problems or concerns.
+
+Each version is given a distinguishing version number. If the Library
+specifies a version number of this License which applies to it and
+``any later version'', you have the option of following the terms and
+conditions either of that version or of any later version published by
+the Free Software Foundation. If the Library does not specify a
+license version number, you may choose any version ever published by
+the Free Software Foundation.
+
+@item
+If you wish to incorporate parts of the Library into other free
+programs whose distribution conditions are incompatible with these,
+write to the author to ask for permission. For software which is
+copyrighted by the Free Software Foundation, write to the Free
+Software Foundation; we sometimes make exceptions for this. Our
+decision will be guided by the two goals of preserving the free status
+of all derivatives of our free software and of promoting the sharing
+and reuse of software generally.
+
+@center @b{NO WARRANTY}
+
+@item
+BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO
+WARRANTY FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE LAW.
+EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR
+OTHER PARTIES PROVIDE THE LIBRARY ``AS IS'' WITHOUT WARRANTY OF ANY
+KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE
+LIBRARY IS WITH YOU. SHOULD THE LIBRARY PROVE DEFECTIVE, YOU ASSUME
+THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+@item
+IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
+WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY
+AND/OR REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE LIABLE TO YOU
+FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
+CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
+LIBRARY (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
+RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
+FAILURE OF THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
+SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+DAMAGES.
+@end enumerate
+
+@subheading END OF TERMS AND CONDITIONS
+
+@page
+@subheading How to Apply These Terms to Your New Libraries
+
+ If you develop a new library, and you want it to be of the greatest
+possible use to the public, we recommend making it free software that
+everyone can redistribute and change. You can do so by permitting
+redistribution under these terms (or, alternatively, under the terms of the
+ordinary General Public License).
+
+ To apply these terms, attach the following notices to the library. It is
+safest to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least the
+``copyright'' line and a pointer to where the full notice is found.
+
+@smallexample
+@var{one line to give the library's name and an idea of what it does.}
+Copyright (C) @var{year} @var{name of author}
+
+This library is free software; you can redistribute it and/or modify it
+under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or (at
+your option) any later version.
+
+This library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+USA.
+@end smallexample
+
+Also add information on how to contact you by electronic and paper mail.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a ``copyright disclaimer'' for the library, if
+necessary. Here is a sample; alter the names:
+
+@smallexample
+Yoyodyne, Inc., hereby disclaims all copyright interest in the library
+`Frob' (a library for tweaking knobs) written by James Random Hacker.
+
+@var{signature of Ty Coon}, 1 April 1990
+Ty Coon, President of Vice
+@end smallexample
+
+That's all there is to it!
diff --git a/python/doc/tutorial.texi b/python/doc/tutorial.texi
@@ -0,0 +1,441 @@
+\input texinfo @c -*-texinfo-*-
+@c %**start of header
+@setfilename tutorial.info
+@include version.texi
+@settitle The GNU Taler tutorial for Web shop developers @value{VERSION}
+
+@c Define a new index for options.
+@defcodeindex op
+@c Combine everything into one index (arbitrarily chosen to be the
+@c concept index).
+@syncodeindex op cp
+@c %**end of header
+
+@copying
+This tutorial is about implementing a merchant frontend to run against a
+GNU Taler merchant backend (version @value{VERSION}, @value{UPDATED}),
+
+Copyright @copyright{} 2016 INRIA
+
+@quotation
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts. A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+@end quotation
+@end copying
+@c If your tutorial is published on paper by the FSF, it should include
+@c The standard FSF Front-Cover and Back-Cover Texts, as given in
+@c maintain.texi.
+@c
+@c Titlepage
+@c
+@titlepage
+@title The GNU Taler tutorial for Web shops
+@subtitle Version @value{VERSION}
+@subtitle @value{UPDATED}
+@author Marcello Stanisci (@email{marcello.stanisci@@inria.fr})
+@page
+@vskip 0pt plus 1filll
+@insertcopying
+@end titlepage
+
+@summarycontents
+@contents
+
+@ifnottex
+@node Top
+@top The GNU Taler tutorial for Web shops
+@insertcopying
+@end ifnottex
+
+@menu
+* Introduction:: Whom this tutorial is addressed to
+* Hello-world:: How to set up a donation page
+* Run How to run the code samples
+
+
+Appendices
+
+* GNU-LGPL:: The GNU Lesser General Public License says how you
+ can use the code of libtalermerchant.so in your own projects.
+* GNU-FDL:: The GNU Free Documentation License says how you
+ can copy and share the documentation of GNU Taler.
+
+Indices
+
+* Concept Index:: Index of concepts and programs.
+@end menu
+
+
+@node Introduction
+@chapter Introduction
+
+@section About GNU Taler
+
+GNU Taler is an open protocol for an electronic payment system with a
+free software reference implementation. GNU Taler offers secure, fast
+and easy payment processing using well understood cryptographic
+techniques. GNU Taler allows customers to remain anonymous, while
+ensuring that merchants can be held accountable by governments.
+Hence, GNU Taler is compatible with anti-money-laundering (AML) and
+know-your-customer (KYC) regulation, as well as data protection
+regulation (such as GDPR).
+
+
+@section About this tutorial
+
+This tutorial is for Web developers and addresses how to integrate GNU
+Taler with Web shops. It describes how to create a Web shop that
+processes payments with the help of a GNU Taler merchant
+@emph{backend}. In the second chapter, you will learn how to trigger
+the payment process from the Web site, how to communicate with the
+backend, how to generate a contract and process the payment.
+
+@cindex examples
+@cindex git
+You can download all of the code examples given in this tutorial from
+@url{https://git.taler.net/merchant-frontend-examples.git/tree/python/example/}.
+
+@c Add section giving an overview of what we will do in the tutorial!
+
+
+@section Architecture overview
+
+The Taler software stack for a merchant consists of the following
+main components:
+
+@itemize
+@cindex frontend
+@item A frontend which interacts with the customer's browser. The
+ frontend enables the customer to build a shopping cart and place
+ an order. Upon payment, it triggers the respective business logic
+ to satisfy the order. This component is not included with Taler,
+ but rather assumed to exist at the merchant. This tutorial
+ describes how to develop a Taler frontend.
+@cindex backend
+@item A Taler-specific payment backend which makes it easy for the
+ frontend to process financial transactions with Taler. For this
+ tutorial, you will use a public backend, but for a production
+ deployment a merchant-specific backend will need to be setup
+ by a system administrator.
+@end itemize
+
+The following image illustrates the various interactions of these
+key components:
+
+@image{arch_nobo, 3in, 4in}
+
+
+Basically, the backend provides the cryptographic protocol support,
+stores Taler-specific financial information and communicates
+with the GNU Taler exchange over the Internet. The frontend accesses
+the backend via a RESTful API. As a result, the frontend never has to
+directly communicate with the exchange, and also does not deal with
+sensitive data. In particular, the merchant's signing keys and bank
+account information are encapsulated within the Taler backend.
+
+@node Hello-world
+@chapter Setting up a simple donation page
+
+This section describes how to setup a simple shop, which exposes a
+button to get donations via Taler. The expected behaviour is that once
+the ``donate'' button is clicked, the customer will receive a Taler
+proposal offering him the opportunity to make a fixed donation,
+for example to donate 1.0 KUDOS to the charity operating the shop.
+
+All the code samples shown below in the tutorial can be found at
+@url{https://git.taler.net/merchant-frontend-examples.git/tree/python/example/}.
+Each sample is part of a 100% functional frontend that the reader
+can run and modify to suit their needs.
+The language is Python, and the Web is served by Flask.
+
+@c NOTE: include explaining wallet installation to Web developer here!
+
+A error message will be prompted to the user if no Taler wallet is
+installed in the browser.
+
+@section Specifying the backend
+
+@cindex backend
+@cindex configuration
+@cindex currency
+For many critical operations, the frontend needs to communicate
+with a Taler backend. Assuming that you do not yet have a backend
+configured, you can use the public backend provided by the Taler
+project for testing. This public backend has been set-up at
+@code{http://backend.test.taler.net/} specifically for testing
+frontends. It uses the currency ``PUDOS'' and all payments will
+go into the ``Tutorial'' account at the Taler ``bank'' running at
+@code{https://bank.test.taler.net/public-accounts}.
+
+In our example, backend and currency are specified by setting two
+global variables, as shown below.
+
+@smallexample
+..
+CURRENCY = "PUDOS"
+BACKEND_URL = "http://backend.test.taler.net/"
+..
+@end smallexample
+
+
+@section Talking to the backend
+
+@cindex backend
+The frontend only needs to issue HTTP POST requests to the backend;
+this is easily made by the `requests` library. See below.
+
+
+@smallexample
+import flask
+import requests
+from urllib.parse import urljoin
+..
+
+# In this example we use the /proposal API offered by the
+# backend, which is in charge of signing orders.
+r = requests.post(urljoin(BACKEND_URL, 'proposal'), json=dict(order=order))
+
+if r.status_code != 200:
+ logger.error("failed to POST to '%s'", url)
+ return r.text, r.status_code
+
+@end smallexample
+
+@node Prompting for payment
+@section Prompting for payment
+
+@cindex button
+Our goal is to trigger a Taler payment once the customer has clicked
+on a donation button. We will use a button that issues an HTTP GET
+to the frontend @code{/donate.php} URL. For this, the HTML would be as
+follows:
+
+@smallexample
+// ../example/templates/index.html
+@verbatiminclude ../example/templates/index.html
+@end smallexample
+
+When the server-side handler for @code{/donate} receives the form submission,
+it will return a HTML page that will take care of:
+
+@itemize
+@item showing a error message if no wallet is installed
+@item instruct the wallet to download the proposal related to this donation
+@end itemize
+
+The @code{/donate} endpoint would then look like follows.
+
+@cindex pay handler
+@cindex 402
+@cindex X-Taler-Contract-Url
+@smallexample
+@@app.route("/donate")
+def donate():
+ response = flask.Response("No wallet installed!", status=402)
+ response.headers["X-Taler-Contract-Url"] = "/generate-proposal"
+ return response
+@end smallexample
+Whenever the wallet detects the 402 status, it reacts by downloading
+the proposal from @code{/generate-proposal}.
+
+If the wallet is not present, the error message will be shown and
+the Taler headers and the 402 status code ought to be ignored by
+the browser.
+
+@section A helper function to generate the proposed contract
+The next step is then to generate the proposal whenever the
+wallet tries to GET @code{/generate-proposal}. In our example,
+this logic is implemented by the function @code{generate_proposal()},
+as shown below.
+
+@cindex contract
+@smallexample
+..
+CURRENCY = "PUDOS"
+..
+@@app.route("/generate-proposal")
+def generate_proposal():
+ DONATION = amounts.string_to_amount("0.1:%s" % CURRENCY)
+ MAX_FEE = amounts.string_to_amount("0.05:%s" % CURRENCY)
+ order = dict(
+ nonce=flask.request.args.get("nonce"),
+ amount=DONATION,
+ max_fee=MAX_FEE,
+ products=[
+ dict(
+ description="Donation",
+ quantity=1,
+ product_id=0,
+ price=DONATION,
+ ),
+ ],
+ fulfillment_url=make_url("/fulfillment"),
+ merchant=dict(
+ address="nowhere",
+ name="Donation tutorial",
+ jurisdiction="none",
+ ),
+ )
+
+ url = urljoin(BACKEND_URL, "proposal")
+
+ r = requests.post(url, json=dict(order=order))
+ if r.status_code != 200:
+ logger.error("failed to POST to '%s'", url)
+ return r.text, r.status_code
+ proposal_resp = r.json()
+ return flask.jsonify(**proposal_resp)
+@end smallexample
+The function @code{amounts.string_to_amount()} is defined by the
+`pytaler` library, and it's used to convert amount given as strings
+(in the form @code{"1.2:EUR"}) to amount as `dict` (in the form
+@code{@{value:1, fraction:20000000, currency:"EUR"@}}).
+@cindex signature
+@cindex backend
+@cindex proposal
+One important thing that @code{generate_proposal()} needs to do is to
+POST the ``order'' to the backend. This is needed because the backend
+has to fill some missing fields and sign the whole order; once the backend
+has done that, it returns the completed data and its signature to the
+frontend that can eventually relay it to the wallet.
+
+The @code{make_url} function is used to ``attach'' paths to the shop's
+base URL. For example, if the shop is run at @code{https://shop.com},
+then @code{make_url("/path")} would result in @code{https://shop.com/path}.
+
+
+@node Initiating the payment process
+@section Initiating the payment process
+
+@cindex fulfillment URL
+After the wallet has fetched the proposal, the user will be
+given the opportunity to affirm the payment. Assuming the user
+affirms, the browser will navigate to the ``fulfillment_url'' that
+was specified in the offer.
+
+The fulfillment page can be called by users that have already paid for
+the item, as well as by users that have not yet paid at all. The
+fulfillment page must thus use the HTTP session state to detect if the
+payment has been performed already, and if not request payment from
+the wallet.
+
+The fulfillment handler at @code{/fulfillment} will firstly figure out
+if the user has already paid, and if so confirm the donation.
+If the user has not yet paid, it will instead return another ``402 Payment
+Required'' header, requesting the wallet to pay:
+
+@cindex 402 payment required
+@smallexample
+@@app.route("/fulfillment")
+def fulfillment():
+ # Ask the state whether the user has paid or not
+ paid = flask.session.get("paid", False)
+ if paid:
+ return "Thank you!"
+
+ # At this point, the user did not pay yet, so we set some
+ # appropriate HTTP headers that will instruct the wallet to
+ # accomplish the payment
+ response = flask.Response(status=402)
+ response.headers["X-Taler-Contract-Url"] = make_url("/generate-proposal")
+ response.headers["X-Taler-Contract-Query"] = "fulfillment_url"
+ # At this URL the wallet can sand the coins.
+ response.headers["X-Taler-Pay-Url"] = make_url("/pay")
+ # This URL will be visited in case the user has clicked
+ # on someone else's fulfillment URL. As a result, the
+ # user will be prompted by a new proposal.
+ response.headers["X-Taler-Offer-Url"] = make_url("/donate")
+
+ return response
+@end smallexample
+
+@section Receiving payments via Taler
+
+The final next step for the frontend is to accept the payment from the
+wallet. For this, the frontend must implement a payment handler at
+the URI specified in the @code{X-Taler-Pay-Url} header, as explained
+above.
+
+The role of the @code{/pay} handler is to receive the payment
+from the wallet and forward it to the backend. If the backend
+reports that the payment was successful, the handler needs to update
+the session state with the browser to remember that the user paid.
+
+In our example, that is done by the @code{pay} function; see below.
+
+@smallexample
+@@app.route("/pay", methods=["POST"])
+def pay():
+ # Here we get the payment from the wallet. The
+ # "payment" is a JSON containing coins and proposal
+ # signed by the wallet, plus some other metadata.
+ deposit_permission = flask.request.get_json()
+ if deposit_permission is None:
+ e = flask.jsonify(error="no json in body")
+ return e, 400
+
+ # Forwarding the payment to the backend that will cryptographically
+ # verify it.
+ r = requests.post(urljoin(BACKEND_URL, 'pay'), json=deposit_permission)
+
+ if 200 != r.status_code:
+ return r.text, r.status_code
+
+ # The payment went through, so we can set the state as "paid".
+ # Note that once this page will return "200 OK", the wallet will
+ # automatically re-visit the fulfillment page (and get the "Thank
+ # you" message now).
+ flask.session["paid"] = True
+
+ return flask.Response(status=200)
+@end smallexample
+
+@node Run
+@chapter Run
+The file @code{python/example/example.py} contains all the code samples
+seen so far, plus some additional helper function, and it is fully operational.
+It is run as a normal Flask application, by the following commands:
+
+@smallexample
+$ cd python/example/
+$ export FLASK_APP=example.py
+$ flask run
+@end smallexample
+
+At this point you should have the site running at localhost on port 5000.
+
+Before proceeding with a paying experience, you need to withdraw a few coins
+from our demonstration bank running at @code{https://bank.test.taler.net/}.
+After that, you should be able to point your browser at @code{http://localhost:5000/}
+and start making donations!
+
+Please visit @code{https://test.taler.net/} to know how to install the Taler
+wallet.
+
+
+@c **********************************************************
+@c ******************* Appendices *************************
+@c **********************************************************
+
+@node GNU-LGPL
+@unnumbered GNU-LGPL
+@cindex license
+@cindex LGPL
+@include lgpl.texi
+
+@node GNU-FDL
+@unnumbered GNU-FDL
+@cindex license
+@cindex GNU Free Documentation License
+@include fdl-1.3.texi
+
+@node Concept Index
+@unnumbered Concept Index
+
+@printindex cp
+
+@bye
diff --git a/python/doc/version.texi b/python/doc/version.texi
@@ -0,0 +1,4 @@
+@set UPDATED 11 November 2016
+@set UPDATED-MONTH November 2016
+@set EDITION 0.2.0
+@set VERSION 0.2.0
