"%e" floating point format and exponent digits
David Nadlinger
see at klickverbot.at
Wed Feb 20 14:04:31 PST 2013
In Phobos, there are quite a few unit tests (std.format,
std.json, ...) which assume that the %e floating point format
zero-pads the exponent to (at least) two digits.
However, the printf-family functions in the MSVC and MinGW
runtimes pad the exponent to *three* digits. For example,
1.223e+24 is printed as "1.223e+024".
By extension, this also applies to the std.format (and thus
std.stdio) floating point code, which relies on snprintf.
What is the correct fix here? Adjusting those unit tests? Doing
something crazy along the lines of "if (result[$-4] == 'e' &&
result[$-3] == '0') { /+ trim zero +/ }"? (How) Is this handled
on DMD/Win64?
The best way would probably be to just implement floating point
printing in D as well, to isolate our code from such C runtime
implementation differences.
David
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