greaterthan and lessthan syntax error in template about swig HOT 4 CLOSED

It's a known limitation of SWIG's parser that it doesn't handle < or > in constant expressions. Here's a closely related existing bug which gives a bit more background:

http://sourceforge.net/p/swig/bugs/1139/

I don't know of a good general workaround I'm afraid. If you can modify the header being wrapped, then using !(a <= b) instead of (a > b) is an option as <= and >= are handled.

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That bug also hit me in Eigen headers: https://bitbucket.org/eigen/eigen/src/60f8b0f18340337e036b566bc583c77deb52f965/Eigen/src/Core/PlainObjectBase.h?at=default&fileviewer=file-view-default#PlainObjectBase.h-142

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I wondered if we could at least support < and > when in a subexpression inside ( ... ) which looks like it would cover all the examples here, in #635 and in the older linked issue in the SF tracker. The Eigen link above doesn't work for me now so I can't easily check that. This wouldn't be a completely perfect solution, but would fix some cases.

I had a quick try and managed to avoid introducing any reduce/reduce conflicts (which is great) but handling < introduces 2 new shift/reduce conflicts (which we ideally want to avoid). I'll mull this over and see if I can figure out how to make it work without any new conflicts, but if someone with bison expertise wants to take a look please say.

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Great tactical solution @ojwb

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