Re: [Groff] pic: nasty little trap in function!

[Werner LEMBERG]

>  Tadziu Hoffmann wrote:
>  a better definition would have been:
> define d2r {($1)*pi/180}
> 

> Yes.  Macros are expanded by simple textual substitution. They are
> totally disconnected from the language syntax.  It is a cardinal
> rule that parameters which you see as subexpressions in formulas be
> parenthesized in the macro definition to assure that they are
> treated as such regardless of what is substituted.  The same rule
> applies to macros in C and troff.  We all learn it the hard way.

:-)   The recommendation to use parentheses is explicitly mentioned in
the pic manual, section 14 (`Macros').


    Werner