[CMake] math(EXPR) and unary operators

[j s]

Make sure you set the precedence and associativity of this operator.
Look for the prec declaration and resulting rule at:
http://www.gnu.org/software/bison/manual/html_node/Infix-Calc.html

For example:
     /* Bison declarations.  */
     %token NUM
     %left '-' '+'
     %left '*' '/'
     %left NEG     /* negation--unary minus */
     %right '^'    /* exponentiation */

and

     exp:      NUM                { $$ = $1;         }
             | exp '+' exp        { $$ = $1 + $3;    }
             | exp '-' exp        { $$ = $1 - $3;    }
             | exp '*' exp        { $$ = $1 * $3;    }
             | exp '/' exp        { $$ = $1 / $3;    }
             | '-' exp  %prec NEG { $$ = -$2;        }
             | exp '^' exp        { $$ = pow ($1, $3); }
             | '(' exp ')'        { $$ = $2;         }
     ;

Regards,

Juan


On Tue, Mar 6, 2012 at 4:05 PM, George Koehler <xkernigh at netscape.net> wrote:
> math(EXPR) rejects expressions with negative numbers. This is awful because
> math() can reject its own negative results. For example, this code fails:
>
>  math(EXPR negative "1 - 2")
>  math(EXPR sum "100 + ${negative}")
>
> The second expression, "100 + -1", causes an error.
>
> This contradicts cmake --help-command math, which claims, "Supported
> operators are + - * / % | & ^ ~ << >> * / %.  They have the same meaning as
> they do in c code."
>
> I can write -2 or ~2 in C, but not in CMake. The ~ (bitwise not) seems
> impossible to use. My every attempt to use ~ in math() causes an error.
>
> To fix this bug, I taught the grammar about unary operators:
>
> diff --git a/Source/cmExprParser.y b/Source/cmExprParser.y
> index 317b0ba..57820ec 100644
> --- a/Source/cmExprParser.y
> +++ b/Source/cmExprParser.y
> @@ -150,6 +150,16 @@ term exp_MOD factor
>  {$<Number>$ = $<Number>1 % $<Number>3;}
>
>  factor:
> +value
> +{$<Number>$ = $<Number>1;}
> +|
> +exp_MINUS factor
> +{$<Number>$ = -$<Number>2;}
> +|
> +exp_NOT factor
> +{$<Number>$ = ~$<Number>2;}
> +
> +value:
>  exp_NUMBER
>  {$<Number>$ = $<Number>1;}
>  |
>
> I pasted this same patch at http://pastebin.com/7j5Pu3AL
>
> After applying this patch, one must run the bison command from the comment
> in cmExprParser.y.
>
> --George Koehler
>
> --
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