nltk.ccg.api module

class nltk.ccg.api.AbstractCCGCategory

Bases: object

Interface for categories in combinatory grammars.

abstractmethod can_unify(other)

Determines whether two categories can be unified.

• Returns None if they cannot be unified

• Returns a list of necessary substitutions if they can.

abstractmethod is_function()

Returns true if the category is a function application.

abstractmethod is_primitive()

Returns true if the category is primitive.

abstractmethod is_var()

Returns true if the category is a variable.

abstractmethod substitute(substitutions)

Takes a set of (var, category) substitutions, and replaces every occurrence of the variable with the corresponding category.

class nltk.ccg.api.CCGVar

Bases: AbstractCCGCategory

Class representing a variable CCG category. Used for conjunctions (and possibly type-raising, if implemented as a unary rule).

__init__(prim_only=False)

Initialize a variable (selects a new identifier)

Parameters:

prim_only (bool) – a boolean that determines whether the variable is restricted to primitives

can_unify(other)

If the variable can be replaced with other a substitution is returned.

id()

is_function()

Returns true if the category is a function application.

is_primitive()

Returns true if the category is primitive.

is_var()

Returns true if the category is a variable.

classmethod new_id()

A class method allowing generation of unique variable identifiers.

classmethod reset_id()

substitute(substitutions)

If there is a substitution corresponding to this variable, return the substituted category.

class nltk.ccg.api.Direction

Bases: object

Class representing the direction of a function application. Also contains maintains information as to which combinators may be used with the category.

__init__(dir, restrictions)

can_compose()

can_cross()

can_unify(other)

dir()

is_backward()

is_forward()

is_variable()

restrs()

A list of restrictions on the combinators. ‘.’ denotes that permuting operations are disallowed ‘,’ denotes that function composition is disallowed ‘_’ denotes that the direction has variable restrictions. (This is redundant in the current implementation of type-raising)

substitute(subs)

class nltk.ccg.api.FunctionalCategory

Bases: AbstractCCGCategory

Class that represents a function application category. Consists of argument and result categories, together with an application direction.

__init__(res, arg, dir)

arg()

can_unify(other)

Determines whether two categories can be unified.

• Returns None if they cannot be unified

• Returns a list of necessary substitutions if they can.

dir()

is_function()

Returns true if the category is a function application.

is_primitive()

Returns true if the category is primitive.

is_var()

Returns true if the category is a variable.

res()

substitute(subs)

Takes a set of (var, category) substitutions, and replaces every occurrence of the variable with the corresponding category.

class nltk.ccg.api.PrimitiveCategory

Bases: AbstractCCGCategory

Class representing primitive categories. Takes a string representation of the category, and a list of strings specifying the morphological subcategories.

__init__(categ, restrictions=[])

can_unify(other)

Determines whether two categories can be unified.

• Returns None if they cannot be unified

• Returns a list of necessary substitutions if they can.

categ()

is_function()

Returns true if the category is a function application.

is_primitive()

Returns true if the category is primitive.

is_var()

Returns true if the category is a variable.

restrs()

substitute(subs)

Takes a set of (var, category) substitutions, and replaces every occurrence of the variable with the corresponding category.