hfst.rules Namespace Reference

rules... More...

Functions
def	coercion
	A transducer that requires that one of the mappings defined by mapping must occur in each context in contexts. More...
def	deep_coercion
	A transducer that specifies that a string from the output language of the transducer mapping always has to be mapped to one of its input strings (according to transducer mappings) if it appears in any of the contexts in contexts. More...
def	deep_restriction
	A transducer that specifies that a string from the output language of the transducer mapping may only be mapped to one of its input strings (according to transducer mappings) if it appears in any of the contexts in contexts.Symbols outside of the matching substrings are mapped to any symbol allowed by alphabet. More...
def	deep_restriction_and_coercion
	A transducer that is equivalent to the intersection of deep_restriction and deep_coercion. More...
def	left_replace_down
	Inversion of the replace_up and the result needs to be composed on the upper side of the input language. More...
def	left_replace_down_karttunen
	Inversion of the replace_up and the result needs to be composed on the upper side of the input language. More...
def	left_replace_left
	Inversion of the replace_up and the result needs to be composed on the upper side of the input language. More...
def	left_replace_right
	Inversion of the replace_up and the result needs to be composed on the upper side of the input language. More...
def	left_replace_up
	Inversion of the replace_up and the result needs to be composed on the upper side of the input language. More...
def	left_replace_up
	Inversion of the replace_up and the result needs to be composed on the upper side of the input language. More...
def	replace_down
	The same as replace_up, but matching is done on the output side of mapping. More...
def	replace_down
	The same as replace_down(context, mapping, optional, alphabet) but mapping is performed in every context. More...
def	replace_down_karttunen
	TODO: document. More...
def	replace_left
	The same as replace_up, but left context matching is done on the output side of mapping and right context on the input side of mapping. More...
def	replace_right
	The same as replace_up, but left context matching is done on the input side of mapping and right context on the output side of mapping. More...
def	replace_up
	A transducer that performs an upward mapping mapping in the context context when the alphabet is alphabet. More...
def	replace_up
	The same as replace_up but mapping is performed in every context. More...
def	restriction
	A transducer that allows any (substring) mapping defined by mapping only if it occurs in any of the contexts in contexts. More...
def	restriction_and_coercion
	A transducer that is equivalent to the intersection of restriction and coercion and requires that the mappings defined by mapping occur always and only in the given contexts in contexts. More...
def	surface_coercion
	A transducer that specifies that a string from the input language of the transducer mapping always has to the mapped to one of its output strings according to transducer mapping if it appears in any of the contexts in contexts. More...
def	surface_restriction
	A transducer that specifies that a string from the input language of the transducer mapping may only be mapped to one of its output strings (according to transducer mapping) if it appears in any of the contexts in contexts. More...
def	surface_restriction_and_coercion
	A transducer that is equivalent to the intersection of surface_restriction and surface_coercion. More...
def	two_level_if
	A transducer that obligatorily performs the mappings defined by mappings in the context context when the alphabet is alphabet. More...
def	two_level_if_and_only_if
	A transducer that always performs the mappings defined by mappings in the context context and only in that context, when the alphabet is alphabet. More...
def	two_level_only_if
	A transducer that allows the mappings defined by mappings only in the context context, when the alphabet is alphabet. More...

Detailed Description

rules...

Function Documentation

def hfst.rules.coercion	(		contexts,
			mapping,
			alphabet
	)

A transducer that requires that one of the mappings defined by mapping must occur in each context in contexts.

Symbols outside of the matching substrings are mapped to any symbol allowed by alphabet.

See also

SFST manual.

Parameters

contexts	A tuple of HfstTransducer pairs.
mapping	An HfstTransducer.
alphabet	A tuple of string pairs.

def hfst.rules.deep_coercion	(		contexts,
			mapping,
			alphabet
	)

A transducer that specifies that a string from the output language of the transducer mapping always has to be mapped to one of its input strings (according to transducer mappings) if it appears in any of the contexts in contexts.

Symbols outside of the matching substrings are mapped to any symbol allowed by alphabet.

See also

SFST manual.

Parameters

contexts	A tuple of HfstTransducer pairs.
mapping	An HfstTransducer.
alphabet	A tuple of string pairs.

def hfst.rules.deep_restriction	(		contexts,
			mapping,
			alphabet
	)

A transducer that specifies that a string from the output language of the transducer mapping may only be mapped to one of its input strings (according to transducer mappings) if it appears in any of the contexts in contexts.Symbols outside of the matching substrings are mapped to any symbol allowed by alphabet.

See also

SFST manual.

Parameters

contexts	A tuple of HfstTransducer pairs.
mapping	An HfstTransducer.
alphabet	A tuple of string pairs.

def hfst.rules.deep_restriction_and_coercion	(		contexts,
			mapping,
			alphabet
	)

A transducer that is equivalent to the intersection of deep_restriction and deep_coercion.

See also

deep_restriction deep_coercion SFST manual.

Parameters

contexts	A tuple of HfstTransducer pairs.
mapping	An HfstTransducer.
alphabet	A tuple of string pairs.

def hfst.rules.left_replace_down	(		context,
			mapping,
			optional,
			alphabet
	)

Inversion of the replace_up and the result needs to be composed on the upper side of the input language.

However, matching is done on the output side of mapping.

See also

replace_up

def hfst.rules.left_replace_down_karttunen	(		context,
			mapping,
			optional,
			alphabet
	)

Inversion of the replace_up and the result needs to be composed on the upper side of the input language.

However, matching is done on the output side of mapping.

See also

replace_up

def hfst.rules.left_replace_left	(		context,
			mapping,
			optional,
			alphabet
	)

Inversion of the replace_up and the result needs to be composed on the upper side of the input language.

However, left context matching is done on the input side of mapping and right context on the output side of mapping.

See also

replace_up */

def hfst.rules.left_replace_right	(		context,
			mapping,
			optional,
			alphabet
	)

Inversion of the replace_up and the result needs to be composed on the upper side of the input language.

However, left context matching is done on the output side of mapping and right context on the input side of mapping.

See also

replace_up

def hfst.rules.left_replace_up	(		mapping,
			optional,
			alphabet
	)

Inversion of the replace_up and the result needs to be composed on the upper side of the input language.

B <- A is the inversion of A -> B. mapping is performed in every context.

See also

replace_up

def hfst.rules.left_replace_up	(		context,
			mapping,
			optional,
			alphabet
	)

Inversion of the replace_up and the result needs to be composed on the upper side of the input language.

B <- A is the inversion of A -> B.

See also

replace_up

def hfst.rules.replace_down	(		context,
			mapping,
			optional,
			alphabet
	)

The same as replace_up, but matching is done on the output side of mapping.

See also

replace_up SFST manual.

def hfst.rules.replace_down	(		mapping,
			optional,
			alphabet
	)

The same as replace_down(context, mapping, optional, alphabet) but mapping is performed in every context.

See also

replace_up

def hfst.rules.replace_down_karttunen	(		context,
			mapping,
			optional,
			alphabet
	)

TODO: document.

def hfst.rules.replace_left	(		context,
			mapping,
			optional,
			alphabet
	)

The same as replace_up, but left context matching is done on the output side of mapping and right context on the input side of mapping.

See also

replace_up

def hfst.rules.replace_right	(		context,
			mapping,
			optional,
			alphabet
	)

The same as replace_up, but left context matching is done on the input side of mapping and right context on the output side of mapping.

See also

replace_up SFST manual.

def hfst.rules.replace_up	(		context,
			mapping,
			optional,
			alphabet
	)

A transducer that performs an upward mapping mapping in the context context when the alphabet is alphabet.

optional defines whether the mapping is optional.

Parameters

context	A pair of transducers where the first transducer defines the left context and the second transducer the right context. Both transducers must be automata, i.e. map strings onto themselves.
mapping	The mapping (transducer) that the resulting transducer will perform in the context given in context.
optional	Whether the mapping is optional.
alphabet	The set of symbol pairs that defines the alphabet (a tuple of string pairs).

Each substring s of the input string which is in the input language of the transducer mapping and whose left context is matched by the expression [.* l] (where l is the first element of context) and whose right context is matched by [r .*] (where r is the second element in the context) is mapped to the respective surface strings defined by transducer mapping. Any other character is mapped to the characters specified in alphabet. The left and right contexts must be automata (i.e. transducers which map strings onto themselves).

For example, a transducer yielded by the following arguments (in pseudocode)

 context = pair( [c], [c] )
 mappings = [ a:b a:b ]
 alphabet = set(a, b, c)

would map the string "caacac" to "cbbcac".

Note that the alphabet must contain the characters a and b, but not the pair a:b (unless this replacement is to be allowed everywhere in the context).

Note that replace operations (unlike the two-level rules) have to be combined by composition rather than intersection.

Exceptions

ContextTransducersAreNotAutomataException

See also

SFST manual

def hfst.rules.replace_up	(		mapping,
			optional,
			alphabet
	)

The same as replace_up but mapping is performed in every context.

See also

replace_up

def hfst.rules.restriction	(		contexts,
			mapping,
			alphabet
	)

A transducer that allows any (substring) mapping defined by mapping only if it occurs in any of the contexts in contexts.

Symbols outside of the matching substrings are mapped to any symbol allowed by alphabet.

Exceptions

EmptySetOfContextsException

See also

SFST manual.

Parameters

contexts	A tuple of HfstTransducer pairs.
mapping	An HfstTransducer.
alphabet	A tuple of string pairs.

def hfst.rules.restriction_and_coercion	(		contexts,
			mapping,
			alphabet
	)

A transducer that is equivalent to the intersection of restriction and coercion and requires that the mappings defined by mapping occur always and only in the given contexts in contexts.

Symbols outside of the matching substrings are mapped to any symbol allowed by alphabet.

See also

restriction coercion SFST manual

Parameters

contexts	A tuple of HfstTransducer pairs.
mapping	An HfstTransducer.
alphabet	A tuple of string pairs.

def hfst.rules.surface_coercion	(		contexts,
			mapping,
			alphabet
	)

A transducer that specifies that a string from the input language of the transducer mapping always has to the mapped to one of its output strings according to transducer mapping if it appears in any of the contexts in contexts.

Symbols outside of the matching substrings are mapped to any symbol allowed by alphabet.

See also

SFST manual.

Parameters

contexts	A tuple of HfstTransducer pairs.
mapping	An HfstTransducer.
alphabet	A tuple of string pairs.

def hfst.rules.surface_restriction	(		contexts,
			mapping,
			alphabet
	)

A transducer that specifies that a string from the input language of the transducer mapping may only be mapped to one of its output strings (according to transducer mapping) if it appears in any of the contexts in contexts.

Symbols outside of the matching substrings are mapped to any symbol allowed by alphabet.

See also

SFST manual.

Parameters

contexts	A tuple of HfstTransducer pairs.
mapping	An HfstTransducer.
alphabet	A tuple of string pairs.

def hfst.rules.surface_restriction_and_coercion	(		contexts,
			mapping,
			alphabet
	)

A transducer that is equivalent to the intersection of surface_restriction and surface_coercion.

See also

surface_restriction surface_coercion SFST manual.

Parameters

contexts	A tuple of HfstTransducer pairs.
mapping	An HfstTransducer.
alphabet	A tuple of string pairs.

def hfst.rules.two_level_if	(		context,
			mappings,
			alphabet
	)

A transducer that obligatorily performs the mappings defined by mappings in the context context when the alphabet is alphabet.

Parameters

context	A pair of transducers where the first transducer defines the left context and the second transducer the right context.
mappings	A set of mappings (a tuple of string pairs) that the resulting transducer will perform in the context given in context.
alphabet	The set of symbol pairs (a tuple of string pairs) that defines the alphabet (see the example).

For example, a transducer yielded by the following arguments (in pseudcode)

 context = pair( [c|d], [e] )
 mappings = set(a:b)
 alphabet = set(a, a:b, b, c, d, e, ...)

obligatorily maps the symbol a to b if c or d precedes and e follows. (Elsewhere, the mapping of a to b is optional). This expression is identical to ![.* [c|d] [a:. & !a:b] [e] .*] Note that the alphabet must contain the pair a:b here.

See also

SFST manual

def hfst.rules.two_level_if_and_only_if	(		context,
			mappings,
			alphabet
	)

A transducer that always performs the mappings defined by mappings in the context context and only in that context, when the alphabet is alphabet.

If called with the same arguments as in the example of two_level_if, the transducer maps symbol a to b only and only if c or d precedes and e follows. The mapping of a to b is obligatory in this context and cannot occur in any other context.

The expression is equivalent to ![.* [c|d] [a:. & !a:b] [e] .*] & ![ [ ![.* [c|d]] a:b .* ] | [ .* a:b ![[e] .*] ] ]

See also

two_level_if

def hfst.rules.two_level_only_if	(		context,
			mappings,
			alphabet
	)

A transducer that allows the mappings defined by mappings only in the context context, when the alphabet is alphabet.

If called with the same arguments as in the example of two_level_if, the transducer allows the mapping of symbol a to b only if c or d precedes and e follows. The mapping of a to b is optional in this context but cannot occur in any other context.

The expression is equivalent to ![ [ ![.* [c|d]] a:b .* ] | [ .* a:b ![[e] .*] ] ]

See also

two_level_if