gen_fst v0.4.1 GenFST View Source

GenFST implements a generic finite state transducer with customizable rules expressed in a DSL.

A finite-state transducer (FST) is a finite-state machine with two memory tapes, following the terminology for Turing machines: an input tape and an output tape.

A FST will read a set of strings on the input tape and generates a set of relations on the output tape. An FST can be thought of as a translator or relater between strings in a set.

In morphological parsing, an example would be inputting a string of letters into the FST, the FST would then output a string of morphemes.

Example

Here we implement a simple morphological parser for English language. This morphological parser recognize different inflectional morphology of the verbs.

fst = GenFST.new
|> GenFST.rule(["play", {"s", "^s"}])
|> GenFST.rule(["act", {"s", "^s"}])
|> GenFST.rule(["act", {"ed", "^ed"}])
|> GenFST.rule(["act", {"ing", ""}])

assert "play^s" == fst |> GenFST.parse("plays")

For example if we pass the third-person singluar tense of the verb act, GenFST.parse(fst, "acts"), the morphological parser will output "act^s". The semantic of rule definition is given at rule/2.

Link to this section Summary

Types

fst()

fst_rule()

Functions

new()

Create a new finite state transducer

parse(fst, input)

Parse the input by transducing it with the given fst

rule(fst, r)

Define a transducing rule, adding it to the fst

Link to this section Types

fst()

fst

fst_rule()

fst_rule() :: String.t | {String.t, String.t}

Link to this section Functions

new()

new() :: fst

Create a new finite state transducer.

See example usage in Module Example

parse(fst, input)

parse(fst, String.t) :: String.t

Parse the input by transducing it with the given fst.

See example usage in Module Example

rule(fst, r)

rule(fst, [fst_rule]) :: fst

Define a transducing rule, adding it to the fst

A transducing rule is a List of String.t | {String.t, String.t}.

For example: rule fst, ["play", {"s", "^s"}] means outputing "play" verbatimly, and transform "s" into "^s". If a finite state transducer built with this rule is fed with string "plays", then the output will be "play^s"

See example usage in Module Example