Constant functions
Bases: sage.structure.sage_object.SageObject
A class for function objects implementing constant functions.
EXAMPLES:
sage: f = ConstantFunction(3)
sage: f
The constant function (...) -> 3
sage: f()
3
sage: f(5)
3
Such a function could be implemented as a lambda expression, but this is not (currently) picklable:
sage: g = lambda x: 3
sage: g == loads(dumps(g))
Traceback (most recent call last):
...
PicklingError: Can't pickle <type 'function'>: attribute lookup __builtin__.function failed
sage: f == loads(dumps(f))
True
Also, in the long run, the information that this function is constant could be used by some algorithms.
TODO:
TESTS:
These tests do fail if we try to use UniqueRepresentation:
sage: f = ConstantFunction(True)
sage: g = ConstantFunction(1)
sage: f(), g()
(True, 1)
That’s because 1 and True cannot be distinguished as keys in a dictionary (argl!):
sage: { 1: 'a', True: 'b' }
{1: 'b'}