Expand elementary functions in math module

[ZibingZhang]

feature is completed, just needs more tests

Overview

Adds more functions which can be expanded.

Details

References

#65

Blocked by

None

[ZibingZhang]

Not sure how much test coverage is best, but I've decided it might be easiest to test the base expansion in function_expander_test (as well as in regression_test), and that testing that nested functions get expanded properly should be done in regression_test. This is so we don't have to deal with constructing asts by hand.

Not sure what the best way to test that for all these functions you need exactly n arguments. The last PR used the test method test_hypot_expanded_no_args, but it'd be nice if there was a way to specify any number of args except for n would raise an error.

Also maybe it would be nice to include an ast_utils.make_name, that way we can stop setting ctx=ast.Load() for every single one of them.

[odashi]

Great, thanks!