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|
(** Sonority module for determining the sonority of phonetic segments.
This module provides functionality to determine the sonority of IPA
(International Phonetic Alphabet) segments on a scale of 1 to 9, where:
- 9: Low vowels (most sonorous)
- 8: High vowels
- 7: Glides/approximants
- 6: Liquids
- 5: Nasals
- 4: Voiced fricatives
- 3: Voiceless fricatives
- 2: Voiced stops
- 1: Voiceless stops (least sonorous) *)
(** Decision tree for computing sonority values *)
type bool_tree =
| Leaf of int (** Terminal node with sonority value *)
| Node of {
test : Feature.segment -> bool; (** Test function *)
t_branch : bool_tree; (** Branch to follow if test is true *)
f_branch : bool_tree; (** Branch to follow if test is false *)
}
(** Main Sonority module functionality *)
module Sonority = struct
(** Initialize the module by loading IPA data *)
let init data_dir =
let csv_file = Filename.concat data_dir "ipa_all.csv" in
Ipa_table.load_csv csv_file
(** Build the decision tree for sonority calculation *)
let build_tree () =
let open Feature in
let plusSyl = test (Syllabic, Plus) in
let minusHi = test (High, Minus) in
let minusCons = test (Consonantal, Minus) in
let plusSon = test (Sonorant, Plus) in
let minusNas = test (Nasal, Minus) in
let plusCont = test (Continuant, Plus) in
let plusVoi = test (Voiced, Plus) in
(* Build the tree bottom-up *)
let minusHi_branch =
Node
{
test = minusHi;
t_branch = Leaf 9;
(* -hi vowels = low vowels *)
f_branch = Leaf 8;
(* +hi vowels = high vowels *)
}
in
let plusVoi1_branch =
Node
{
test = plusVoi;
t_branch = Leaf 4;
(* +voi +cont = voiced fricatives *)
f_branch = Leaf 3;
(* -voi +cont = voiceless fricatives *)
}
in
let plusVoi2_branch =
Node
{
test = plusVoi;
t_branch = Leaf 2;
(* +voi -cont = voiced stops *)
f_branch = Leaf 1;
(* -voi -cont = voiceless stops *)
}
in
let plusCont_branch =
Node
{
test = plusCont;
t_branch = plusVoi1_branch;
(* +cont = fricatives *)
f_branch = plusVoi2_branch;
(* -cont = stops *)
}
in
let minusNas_branch =
Node
{
test = minusNas;
t_branch = Leaf 6;
(* -nas +son = liquids *)
f_branch = Leaf 5;
(* +nas +son = nasals *)
}
in
let plusSon_branch =
Node
{
test = plusSon;
t_branch = minusNas_branch;
(* +son = sonorants *)
f_branch = plusCont_branch;
(* -son = obstruents *)
}
in
let minusCons_branch =
Node
{
test = minusCons;
t_branch = Leaf 7;
(* -cons = glides *)
f_branch = plusSon_branch;
(* +cons = true consonants *)
}
in
Node
{
test = plusSyl;
t_branch = minusHi_branch;
(* +syl = vowels *)
f_branch = minusCons_branch;
(* -syl = non-vowels *)
}
(** Evaluate the decision tree for a segment *)
let rec eval_tree tree segment =
match tree with
| Leaf value -> value
| Node { test; t_branch; f_branch } ->
if test segment then eval_tree t_branch segment
else eval_tree f_branch segment
(** The main decision tree instance *)
let sonority_tree = lazy (build_tree ())
(** Get sonority value from feature specifications *)
let sonority_from_features segment =
eval_tree (Lazy.force sonority_tree) segment
(** Get sonority value from an IPA character *)
let sonority ipa =
match Ipa_table.lookup_segment ipa with
| Some features -> sonority_from_features features
| None -> failwith (Printf.sprintf "Unknown IPA segment: %s" ipa)
end
(** Public interface *)
(** Initialize the sonority module with the data directory *)
let init = Sonority.init
(** Get the sonority value (1-9) for an IPA character *)
let sonority = Sonority.sonority
(** Get the sonority value from a feature specification *)
let sonority_from_features = Sonority.sonority_from_features
|
