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Re: [PATCHv2 06/14] Replace M_PI2l with pi_2_d in

On Mon, 23 May 2016, Paul E. Murphy wrote:

> > For the API for float128 to be feature-complete compared to long double, 
> > it should include constants such as M_PI_2f128 for all the long double 
> > constants in <math.h>.  Which means that there is always a constant from 
> > <math.h> that can be used in these cases; you don't need yet another copy 
> > of the digits of this constant.  You might, for example, have a macro MCST 
> > defined for each type and use MCST (PI_2) here (which would expand to 
> > M_PI_2 for float and double - there aren't float versions of these 
> > <math.h> constants - M_PI_2l for long double, M_PI_2f128 for float128).
> Are you suggesting removing the new constants entirely, or just redefining
> these macros in terms of existing macros?

My suggestion was removing them entirely (and using MCST (PI_2) etc. in 
individual tests), but I suppose you could define them in terms of 
existing macros.

> I'd prefer to keep the M prefixed constants out of the individual test cases,
> and maintain consistency with the other lower case constants.  It's too easy
> to overlook them otherwise.

Actually, I think there is a case for the following: the individual tests 
all use names that are not M_*, for both the constants that are in 
<math.h> and the local ones - but those names all have some common prefix 
in place of M_, rather than being like the other lower-case constants 
without any fixed prefix.

Rationale: these constants are logically different from those such as 
min_value, in that, when used as expected results, the ideal result would 
depend on the rounding mode.  So having a unique prefix would facilitate 
hypothetical future enhancements to detect such constants 
in expected results and replace them by references to per-rounding-mode 
macros, where the values of those macros are automatically generated for 
each format and rounding modes by gen-auto-libm-tests.c or similar.

Joseph S. Myers

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