expressions: modulus or modulo operator?

[Andreas Albarello]

Michael Schulz wrote:
> When i looked in mapparser.y i found this line:
> 345:  math_exp '%' math_exp   { $$ = (int)$1 * (int)$3; }
> 
> This looks like the modulo operator is defined, but the calculation is
> not modulo.

Michael,

indeed, that isn't modulo nor is it modulus, that's a multiplication of 
two truncated values (hence the (int) typecast). And 
http://trac.osgeo.org/mapserver/changeset/5151 confirms that line in 
mapparser.y is the actual implementation of what was called "modulus 
operator" in HISTORY.TXT.

I'd file a bug report about this, since at least it isn't clear what is 
meant with "modulus" in this instance. If you need the actual modulo 
operator, I'd suggest changing that line to

math_exp '%' math_exp   { $$ = (int)$1 % (int)$3; }

and regenerating the parser with yacc -p msyy -d -omapparser.c mapparser.y.

Best regards,
-- 
--------------------------------------------------------------------
Andreas Albarello
Analysis & SW Development

Territorium Online srl/GmbH
Via Buozzi/Buozzistraße 12 - I 39100 Bolzano/Bozen
email: andreas.albarello at territoriumonline.com
web:   www.territoriumonline.com
--------------------------------------------------------------------