Re: Help fixing parser for negative exponents to **

[Andrew Pinski <pinskia at physics dot uc dot edu>]

On May 24, 2004, at 15:17, Roger Sayle wrote:

> Unfortunately, I don't have access to the official grammars for
> fortran95 and fortran2003, but I suspect that there's a bug in
> gfortran's parser for processing power expressions.  Currently,
> we fail to parse unary minus (and unary plus) expressions
> immediately following an exponentiation/power operator.
>
>        X = 2.0
>        Y = X**-1.5D0
>        PRINT 10, Y
> 10     FORMAT (F8.5)
>        END
>
>        X = 2.0
>        Y = X**+1.5D0
>        PRINT 10, Y
> 10     FORMAT (F8.5)
>        END
>
>        X = 2.0
>        Y = 1.5
>        Z = X**-Y
>        PRINT 10, Z
> 10     FORMAT (F8.5)
>        END
>
>
> I believe these are all valid, and compile fine with g77.  They might
> however be a "common" extension, so I thought I'd check with this list
> first.  The examples in gfortran.fortran-torture/execute/power.f90 all
> use parenthesis around negative exponents.

This is a common extension as if you -pedantic with g77 you get a 
message.
prthgfdhgfds.f: In program `MAIN__':
prthgfdhgfds.f:3:
          Z = X**-Y
               1 2
Two arithmetic operators in a row at (1) and (2) -- use parentheses

And I think this is PR 13912 as the issue is the same with
multiplication also.

Thanks,
Andrew Pinski