GLSL isnan() function not supported on OSX

[orenbum]

OSX only supports up to GLSL v1.20 (see: https://developer.apple.com/graphicsimaging/opengl/capabilities/) which doesn't include the isnan() function. Trying to run the TaggedHeatMapExample results in the following error:

INFO: Compiling 'PIPELINE colormap'...
Mar 15, 2012 7:12:24 PM com.metsci.glimpse.gl.shader.GLShaderUtils logGLShaderInfoLog
WARNING: COMPILATION FAILED: 'FRAGMENT SHADER tagged_colorscale_shader' did not compile.
Mar 15, 2012 7:12:24 PM com.metsci.glimpse.gl.shader.GLShaderUtils logGLShaderInfoLog
WARNING: ERROR: 0:33: Call to undeclared function 'isnan'

I think the only shader this affects is the tagged_colorscale_shader.fs, which uses isnan() to discard values.

[ulmangt]

The call to isnan has been replaced with "x != x" which appears to have the same affect.