Grammalecte  Check-in [debfd84fcd]

            weight += (1 - weight) * ((Num_com - i - 1) / (a_len * b_len - i*2 + 2));
          }
        }

        return weight;
    },

    distanceSift4: function (s1, s2, maxOffset=5) {
        // Sift4 - simplest version : https://siderite.dev/blog/super-fast-and-accurate-string-distance.html
        // online algorithm to compute the distance between two strings in O(n)
        // maxOffset is the number of characters to search for matching letters
        if (!s1 || !s1.length) {
            if (!s2) {
                return 0;
            }
            return s2.length;
        }

        if (!s2 || !s2.length) {
            return s1.length;
        }

        var l1 = s1.length;
        var l2 = s2.length;

        var c1 = 0; //cursor for string 1
        var c2 = 0; //cursor for string 2
        var lcss = 0; //largest common subsequence
        var local_cs = 0; //local common substring
        while ((c1 < l1) && (c2 < l2)) {
            if (s1.charAt(c1) == s2.charAt(c2)) {
                local_cs++;
            } else {
                lcss += local_cs;
                local_cs = 0;
                if (c1 != c2) {
                    c1 = c2 = Math.max(c1, c2); //using max to bypass the need for computer transpositions ('ab' vs 'ba')
                }
                for (var i = 0; i < maxOffset && (c1 + i < l1 || c2 + i < l2); i++) {
                    if ((c1 + i < l1) && (s1.charAt(c1 + i) == s2.charAt(c2))) {
                        c1 += i;
                        local_cs++;
                        break;
                    }
                    if ((c2 + i < l2) && (s1.charAt(c1) == s2.charAt(c2 + i))) {
                        c2 += i;
                        local_cs++;
                        break;
                    }
                }
            }
            c1++;
            c2++;
        }
        lcss += local_cs;
        return Math.round(Math.max(l1, l2) - lcss);
    },

    showDistance (s1, s2) {
        console.log(`Distance Jaro-Winkler: ${s1} / ${s2} = ${this.distanceJaroWinkler(s1, s2)})`);
        console.log(`Distance Damerau-Levenshtein: ${s1} / ${s2} = ${this.distanceDamerauLevenshtein(s1, s2)})`);
    showDistance: function (s1, s2) {
        console.log(`${s1} ≠ ${s2}`);
        let nDL = this.distanceDamerauLevenshtein(s1, s2);
        let nS4 = this.distanceSift4(s1, s2);
        let fJW = this.distanceJaroWinkler(s1, s2);
        console.log(`DL: ${nDL} — S4: ${nS4} — JW: ${fJW}`);
    },

    // Suffix only
    defineSuffixCode: function (sFlex, sStem) {
        /*
            Returns a string defining how to get stem from flexion
                "n(sfx)"

        if nMinLen > 4  and  nCommon > i + 1  and  2 * nCommon >= nMinLen + i:
            fWeight += (1 - fWeight) * ((nCommon - i - 1) / (nLen1 * nLen2 - i*2 + 2))
    return fWeight


def distanceSift4 (s1, s2, nMaxOffset=5):
    "implementation of general Sift4."
    # faster than Damerau-Levenshtein and Jaro-Winkler
    # https://siderite.blogspot.com/2014/11/super-fast-and-accurate-string-distance.html
    # https://siderite.dev/blog/super-fast-and-accurate-string-distance.html
    if not s1:
        return len(s2)
    if not s2:
        return len(s1)
    nLen1, nLen2 = len(s1), len(s2)
    i1, i2 = 0, 0   # Cursors for each string
    nLargestCS = 0  # Largest common substring

            i1 = i2 = min(i1, i2)
    nLargestCS += nLocalCS
    return round(max(nLen1, nLen2) - nLargestCS + nTrans)


def showDistance (s1, s2):
    "display Damerau-Levenshtein distance and Sift4 distance between <s1> and <s2>"
    print("Jaro-Winkler: " + s1 + "/" + s2 + " = " + distanceJaroWinkler(s1, s2))
    print("Damerau-Levenshtein: " + s1 + "/" + s2 + " = " + distanceDamerauLevenshtein(s1, s2))
    print("Sift4:" + s1 + "/" + s2 + " = " + distanceSift4(s1, s2))

    nDL = distanceDamerauLevenshtein(s1, s2)
    nS4 = distanceSift4(s1, s2)
    fJW = distanceJaroWinkler(s1, s2)
    print(s1, "≠", s2, "\tDL:", nDL, "\tS4:", nS4, "\tJW:", fJW)



#### STEMMING OPERATIONS

## No stemming