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| From: | Doug McIlroy |
| Subject: | Re: [Groff] pic: nasty little trap in function! |
| Date: | Mon, 02 Mar 2015 21:41:41 -0500 |
| User-agent: | Heirloom mailx 12.5 7/5/10 |
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.
Doug
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