New in version 2.5.
True when expr is an integer-equivalent number:
abjad> from abjad.tools import mathtools
abjad> mathtools.is_integer_equivalent_expr(12.0)
True
True when expr evaluates to an integer:
abjad> mathtools.is_integer_equivalent_expr('12')
True
Otherwise false:
abjad> mathtools.is_integer_equivalent_expr('foo')
False
Return boolean.