// wink-nlp-utils
// NLP Functions for amplifying negations, managing elisions,
// creating ngrams, stems, phonetic codes to tokens and more.
//
// Copyright (C) GRAYPE Systems Private Limited
//
// This file is part of “wink-nlp-utils”.
//
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// copy of this software and associated documentation files (the "Software"),
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//
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//
var rgx = require( './util_regexes.js' );
// ## string
// ### propagateNegations
/**
*
* It looks for negation tokens in the input array of tokens and propagates
* negation to subsequent `upto` tokens by prefixing them by a `!`. It is useful
* in handling text containing negations during tasks like similarity detection,
* classification or search.
*
* @alias tokens#propagateNegations
* @param {string[]} tokens the input tokens.
* @param {number} [upto=2] number of tokens to be negated after the negation
* token. Note, tokens are only negated either `upto` tokens or up to the token
* preceeding the **`, . ; : ! ?`** punctuations.
* @return {string[]} tokens with negation propagated.
* @example
* propagateNegations( [ 'mary', 'is', 'not', 'feeling', 'good', 'today' ] );
* // -> [ 'mary', 'is', 'not', '!feeling', '!good', 'today' ]
*/
var propagateNegations = function ( tokens, upto ) {
var i, imax, j, jmax;
var tkns = tokens;
var limit = upto || 2;
for ( i = 0, imax = tkns.length; i < imax; i += 1 ) {
if ( rgx.negations.test( tkns[ i ] ) ) {
for ( j = i + 1, jmax = Math.min( imax, i + limit + 1 ); j < jmax; j += 1 ) {
// Hit a punctuation mark, break out of the loop otherwise go *upto the limit*.
// > TODO: promote to utilities regex, after test cases have been added.
if ( ( /[\,\.\;\:\!\?]/ ).test( tkns[ j ] ) ) break;
// Propoage negation: invert the token by prefixing a `!` to it.
tkns[ j ] = '!' + tkns[ j ];
}
i = j;
}
}
return tkns;
}; // propagateNegations()
module.exports = propagateNegations;