commit 3c808661c6552fd2700cd25c42d5ff1e170f87c1
parent dc44d170215db9f843f684ab5a2aae0c44bf743c
Author: Christian Grothoff <christian@grothoff.org>
Date: Fri, 11 Aug 2023 16:30:40 +0200
add STEFAN support to exchange
Diffstat:
3 files changed, 49 insertions(+), 1 deletion(-)
diff --git a/core/api-exchange.rst b/core/api-exchange.rst
@@ -116,6 +116,31 @@ possibly by using HTTPS.
// The exchange's currency or asset unit.
currency: string;
+ // How many digits should the amounts be rendered
+ // with by default. Small capitals should
+ // be used to render fractions beyond the number
+ // given here (like on gas stations).
+ currency_fraction_digits: integer;
+
+ // Absolute cost offset for the STEFAN curve used
+ // to (over) approximate fees payable by amount.
+ stefan_abs: Amount;
+
+ // Factor to multiply the logarithm of the amount
+ // with to (over) approximate fees payable by amount.
+ // Note that the total to be paid is first to be
+ // divided by the smallest denomination to obtain
+ // the value that the logarithm is to be taken of.
+ stefan_log: Amount;
+
+ // Linear cost factor for the STEFAN curve used
+ // to (over) approximate fees payable by amount.
+.
+ // Note that the total to be paid is first to be
+ // divided by the smallest denomination to obtain
+ // the value to be multiplied with.
+ stefan_lin: Amount;
+
// Type of the asset. "fiat", "crypto", "regional"
// or "stock". Wallets should adjust their UI/UX
// based on this value.
diff --git a/design-documents/047-stefan.rst b/design-documents/047-stefan.rst
@@ -38,7 +38,10 @@ Proposed Solution
The proposal is for the exchange to advertise three STEFAN-parameters that
encode a fee curve of the form ``stefan_abs + stefan_log * log P +
-stefan_lin * P`` where P is the price to be paid. The fee curve will be the
+stefan_lin * P`` where P represents the price to be paid.
+Here, the numerical value for P is to be computed by
+dividing the actual price by the smallest denomination
+offered by the exchange. The fee curve will be the
displayed fee, except in cases where the coin selection is exceptionally bad
(which should happen in substantially less than 1% of all cases). The fee
curve will also be used as the maximum fee a merchant will cover unless the
diff --git a/manpages/taler.conf.5.rst b/manpages/taler.conf.5.rst
@@ -113,6 +113,26 @@ ENABLE_REWARDS
rewards is enabled or disabled, and protocol-compliant merchant
backends will then enable or disable the feature accordingly.
+CURRENCY_FRACTION_DIGITS
+ How many digits should amounts be rendered
+ with by default. Small capitals should
+ be used to render fractions beyond the number
+ given here (like on gas stations). Defaults to 0.
+ For EUR and USD, the value would be 2, while for
+ JPY it would be 0.
+
+STEFAN_ABS
+ Absolte amount to use in the STEFAN fee approximation
+ curve (see DD47). Defaults to 0 if not specified.
+
+STEFAN_LOG
+ Logarithmic factor to use in the STEFAN fee approximation
+ curve (see DD47). Defaults to 0 if not specified.
+
+STEFAN_LIN
+ Linear factor to use in the STEFAN fee approximation
+ curve (see DD47). Defaults to 0 if not specified.
+
BASE_URL
The base URL under which the exchange can be reached.
Added to wire transfers to enable tracking by merchants.
