# Coerce maps¶

Coerce maps

class sage.structure.coerce_maps.CCallableConvertMap_class

Bases: sage.categories.map.Map

class sage.structure.coerce_maps.CallableConvertMap

Bases: sage.categories.map.Map

This lets one easily create maps from any callable object.

This is especially useful to create maps from bound methods.

EXAMPLES:

sage: from sage.structure.coerce_maps import CallableConvertMap
sage: def foo(P, x): return x/2
sage: f = CallableConvertMap(ZZ, QQ, foo)
sage: f(3)
3/2
sage: f
Conversion via foo map:
From: Integer Ring
To:   Rational Field


Create a homomorphism from $$\RR$$ to $$\RR^+$$ viewed as additive groups.

sage: f = CallableConvertMap(RR, RR, exp, parent_as_first_arg=False)
sage: f(0)
1.00000000000000
sage: f(1)
2.71828182845905
sage: f(-3)
0.0497870683678639

class sage.structure.coerce_maps.DefaultConvertMap

Bases: sage.categories.map.Map

This morphism simply calls the codomain’s element_constructor method, passing in the codomain as the first argument.

class sage.structure.coerce_maps.DefaultConvertMap_unique

This morphism simply defers action to the codomain’s element_constructor method, WITHOUT passing in the codomain as the first argument.

This is used for creating elements that don’t take a parent as the first argument to their __init__ method, for example, Integers, Rationals, Algebraic Reals... all have a unique parent. It is also used when the element_constructor is a bound method (whose self argument is assumed to be bound to the codomain).

class sage.structure.coerce_maps.ListMorphism

Bases: sage.categories.map.Map

class sage.structure.coerce_maps.NamedConvertMap

Bases: sage.categories.map.Map

This is used for creating a elements via the _xxx_ methods.

For example, many elements implement an _integer_ method to convert to ZZ, or a _rational_ method to convert to QQ.

method_name
class sage.structure.coerce_maps.TryMap

Bases: sage.categories.map.Map

TESTS:

sage: sage.structure.coerce_maps.TryMap(RDF.coerce_map_from(QQ), RDF.coerce_map_from(ZZ))
Traceback (most recent call last):
...
TypeError: incorrectly matching parent

sage.structure.coerce_maps.test_CCallableConvertMap(domain, name=None)

For testing CCallableConvertMap_class.

TESTS:

sage: from sage.structure.coerce_maps import test_CCallableConvertMap
sage: f = test_CCallableConvertMap(ZZ, 'test'); f
Conversion via c call 'test' map:
From: Integer Ring
To:   Integer Ring
sage: f(3)
24
sage: f(9)
720


Coerce actions