Support for special float values

[glennib]

I think this genmsg issue is more appropriate here.

In cases where constants in messages are set to special floats, for example:

float32 a = NaN
float32 p = Inf
float32 n = -Inf 

The successfully generated Python script declare those as:

a = nan
p = inf
n = -inf

However, those causes NameError as nan, inf don't exist.

The following works in Python:

a = float('nan')
p = float('inf')
n = float('-inf')

A suggestion is to add the lines

nan = float('nan')
inf = float('inf')

at the top of the output of msg_generator:

genpy/src/genpy/generator.py

Lines 817 to 821 in 5008399

	yield '# This Python file uses the following encoding: utf-8'
	yield '"""autogenerated by genpy from %s.msg. Do not edit."""' % spec.full_name
	yield 'import sys'
	yield 'python3 = True if sys.hexversion > 0x03000000 else False'
	yield 'import genpy\nimport struct\n'

Another solution would be to have special handling of these types of values at

genpy/src/genpy/generator.py

Line 864 in 5008399

yield ' %s = %s' % (c.name, c.val)

[dirk-thomas]

As stated on the referenced ticket already: please consider to provide a pull request for that enhancement.