On Sat, Jun 15, 2024, 4:56 PM Léa Gris <lea.g...@noiraude.net> wrote:
> On 15/06/2024 à 15:29, Koichi Murase wrote : > > at which point does the conversion happens > > The conversion to LC_NUMERIC format only happens during variable > expansion outside of a numerical context. > The numerical context can be explicit if the assigned variable has a > numeric flag; it is implicit within ((numeric context)) > > Tgere are other numerical context in Bash, like string and array > indexes, but those may retain only integer support. > > > So this means that the arithmetic expansions $(()) would produce a > > format incompatible with the arithmetic expression. This seems > > inconsistent to me, but it might be a valid option if there is no > > other option. > > The numerical context with a $ prefix $(()) indeed implies a string > conversion after resolving the computation within. So yes it would > perform the string conversion using th LC_NUMERIC format. > > An other change is that witin a declare statement or if the assigned > variable has a numeric flag it is considered a numerical context. > > # Numerical context of the assigned pi variable allow use of > # C format of the 3.1415 literal to be used in assignment > declare -i pi=3.1415 > > # give a a numeric flag > typeset -i e > # Because a has a numeric flag it accepts the dot radix delimiter within > # the assigned value > e=2.71828 > > # Numerical context pi / 2 computes to 1.57 > # but as it is expanded into a string, it uses > # the comma radix delimiter from LC_NUMERIC=fr_FR.UTF8 > str=$((pi / 2)) > # Then str=1,57 > > # This is illegal, becahse the right-side is expanded > # to string and may not use the correct dot delimiter > declare -i arc=$(((2 * pi) / 3) > ^ missing a ) # This is a correct assignemnt > ((arc = (2 * pi) / 3)) > > # Although arc has not been declared with a numeric flag > # it was assigned within a numerical context > > > > I feel it is better to allow the printf implementations > > to extend the conversion rather than trying to invent strange and > > inconsistent behaviors among the arithmetic expressions > > I agree this printf limitation is questionable. > > Anyway, given the slow pace of standard evolution and to not break the > standard. Having consideration for the context when manipulation values > or expanding these values to a string can greatly help workaround this > POSIX C restriction. > > It is really a simple rule: > > 1. Within a numerical context, floating-point literals use the dot radix > delimiter. Internally it could yse whatever fit best like IEEE 754 > double precision binary64 > 2. Outside a numerical context, when creating a string representation of > a floating-point number, the LC_NUMERIC format applies. > > -- > Léa Gris > >
