Henning: Indeed, the proposal follows the description in p57-58 of http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf, which dates back to 2007. (Some Haskell related deviations do exist, like dropping the final suffix, since Haskell doesn't need it; and requiring digits both before and after the dot.) I think of the format as precisely representing the value "mantissa x 2^exp"; where the mantissa is written in hexadecimal, and the exponent is left as a regular decimal integer. The discrepancy is rather weird, but I guess it made more sense when the standard was drafted. More importantly, all the other languages (C, Java, Python: http://www.exploringbinary.com/hexadecimal-floating-point-constants/) follow this convention as well; so it would be unfortunate if Haskell diverged. For the change in semantics for "reads:" That is indeed unfortunate since we lose backwards compatibility. But it's a very minor one and I would be curious if anyone depended on the existing semantics for any legitimate reason. I personally do not see any issues with it. -Levent. On Tue, Feb 28, 2017 at 11:20 AM, Henning Thielemann < lemming@henning-thielemann.de> wrote:
On Tue, 28 Feb 2017, Iavor Diatchki wrote:
This may affect existing programs---although it doesn't seem very likely.
Here is an example:
current behavior:
reads "0x10p10" = [(16.0,"p10")]
new behavior:
reads "0x10p10" = [(16384,"")]
"p" refers to a power of two and the exponent is written in decimal for a hexadecimal mantissa. Looks pretty confusing to me but it seems that the standard was made somewhen before this proposal. _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries