Ninja doesn't accept some charaters in variable names (eg. +)

[rgeary1]

Ninja gives a lexing error if I create a build rule with a + in it. This causes difficulty as I'm trying to create a c++0x variant of my build and I have to adjust the target name for ninja

Can you extend the character set allowed in variable names?

[nico]

You can use ${a+b} to refer to variables that the straight $a syntax doesn't allow.

[evmar]

See lexer.in.cc, function ReadToken() for the regex (varname) defining allowed identifiers. I don't think there's any good reason to disallow +, but when I wrote it I wanted to be conservative in case we wanted to use that character for syntax later. I don't have any objection to allowing it, I think.