X-Git-Url: https://git.yukkurigames.com/?p=string-lerp.git;a=blobdiff_plain;f=string-lerp.js;h=5e8201c942e8afa1d29b1949c7e47813ff95acd0;hp=4a2c80f1533cad299063a7bdcc644defa5e5fe8b;hb=a2ba0c21bc1e59f8269051458266896cb928f905;hpb=ce8d91dd9711ad0216e44f8ae69d114bd4fc85c8 diff --git a/string-lerp.js b/string-lerp.js index 4a2c80f..5e8201c 100644 --- a/string-lerp.js +++ b/string-lerp.js @@ -3,54 +3,44 @@ var MAX_MATRIX_SIZE = 256 * 256; - function repeat(n, v) { - var r = []; - while (n--) - r.push(v); - return r; - } - - function createMatrix(i, j) { - var m = []; - while (i--) - m.push(repeat(j, 0)); - return m; - } - function levenshteinMatrix(s, t) { /** Calculate the Levenshtein edit distance matrix for two strings + + The matrix is returned as a flat unsigned typed array. - // Following http://en.wikipedia.org/wiki/Levenshtein_distance + Following http://en.wikipedia.org/wiki/Levenshtein_distance */ var m = s.length + 1; var n = t.length + 1; - var d = createMatrix(m, n); + var d = new Uint32Array(m * n); var i, j; for (i = 1; i < m; ++i) - d[i][0] = i; + d[n * i] = i; for (j = 1; j < n; ++j) - d[0][j] = j; + d[j] = j; for (j = 1; j < n; ++j) for (i = 1; i < m; ++i) if (s[i - 1] === t[j - 1]) - d[i][j] = d[i - 1][j - 1]; + d[n * i + j] = d[n * (i - 1) + j - 1]; else - d[i][j] = 1 + Math.min(d[i - 1][ j ], - d[ i ][j - 1], - d[i - 1][j - 1]); + d[n * i + j] = 1 + Math.min(d[n * (i - 1) + j ], + d[n * i + j - 1], + d[n * (i - 1) + j - 1]); return d; } - function editPath(m, s, t) { - var path = [] - var i = s.length; + function editPath(d, t) { + /** Given a Levenshtein matrix and target, create an edit list */ + var path = []; var j = t.length; + var n = j + 1; + var i = d.length / n - 1; while (i || j) { - var sub = (i && j) ? m[i - 1][j - 1] : Infinity; - var del = i ? m[i - 1][j] : Infinity; - var ins = j ? m[i][j - 1] : Infinity; + var sub = (i && j) ? d[n * (i - 1) + j - 1] : Infinity; + var del = i ? d[n * (i - 1) + j] : Infinity; + var ins = j ? d[n * i + j - 1] : Infinity; if (sub <= ins && sub <= del) { - if (m[i][j] !== m[i - 1][j - 1]) + if (d[n * i + j] !== d[n * (i - 1) + j - 1]) path.push(["sub", i - 1, t[j - 1]]); --i; --j; } else if (ins <= del) { @@ -64,7 +54,13 @@ return path; } - function applyEdits(edits, s, t) { + function diff(s, t) { + /** Create a diff between string s and t */ + return editPath(levenshteinMatrix(s, t), t); + } + + function patch(edits, s) { + /** Apply the list of edits to s */ var i; for (i = 0; i < edits.length; ++i) { var edit = edits[i]; @@ -83,33 +79,112 @@ return s; } - function slowLerp(a, b, p) { - var m = levenshteinMatrix(a, b); - var edits = editPath(m, a, b); + function diffLerp(a, b, p) { + /** Interpolate between two strings based on edit distance + + This interpolation algorithm applys a partial edit of one + string into the other. This produces nice looking results, + but can take a significant amount of time and memory to + compute the edits. It is not recommended for strings + longer than a few hundred characters. + */ + var edits = diff(a, b); var partial = edits.slice(0, Math.round(p * edits.length)); - return applyEdits(partial, a, b); + return patch(partial, a); + } + + var NUMBERS = /(-?\d+(?:\.\d+)?)/g; + + function areNumericTwins(a, b) { + /** Check if a and b differ only in numerals + + A leading "-" counts as part of numbers; a leading "+" + does not. Numbers may contain a single ".", but no other + floating point syntax. + */ + return a.replace(NUMBERS, "0") === b.replace(NUMBERS, "0"); + } + + function nlerp(a, b, p) { + return a + (b - a) * p; + } + + function numericLerp(a, b, p) { + /** Interpolate numerically between two strings containing numbers + + Numbers may have a leading "-" and a single "." to mark + the decimal point, but something must be after the ".". + If both of the numbers in a pair are integers, the result + is clamped to an integer. + + For example, numericLerp("0.0", "100", 0.123) === "12.3" + because the "." in "0.0" is intepreted as a decimal point. + But numericLerp("0.", "100.", 0.123) === "12." because the + strings are interpreted as integers followed by a full + stop. + + Calling this functions on strings that differ in more than + numerals gives undefined results. + */ + var aParts = a.split(NUMBERS); + var bParts = b.split(NUMBERS); + for (var i = 1; i < aParts.length; i += 2) { + var part = nlerp(+aParts[i], +bParts[i], p); + if (aParts[i].indexOf(".") === -1 && bParts[i].indexOf(".") === -1) + part = Math.round(part); + aParts[i] = part.toString(); + } + return aParts.join(""); } function fastLerp(a, b, p) { + /** Interpolate between two strings based on length + + This interpolation algorithm progressively replaces the + front of one string with another. This approach is fast + but does not look good when the strings are similar. + */ var alen = Math.round(a.length * p); var blen = Math.round(b.length * p); return b.substring(0, blen) + a.substring(alen, a.length); } function lerp(a, b, p) { + /** Interpolate between two strings as best as possible + + If the strings are identical aside from numbers in them, + they are passed through numericLerp. + + If the strings are not numbers and short, they are passed + through diffLerp. + + Otherwise, they are passed through fastLerp. + */ a = a.toString(); b = b.toString(); + + // Fast path for boundary cases. + if (p === 0) return a; + if (p === 1) return b; + + if (areNumericTwins(a, b)) + return numericLerp(a, b, p); + + // Numeric lerps should over- and under-shoot when fed numbers + // outside 0 to 1, but other types cannot. + if (p < 0) return a; + if (p > 1) return b; + var n = a.length * b.length; - return (n && n < MAX_MATRIX_SIZE) - ? slowLerp(a, b, p) - : fastLerp(a, b, p); + return ((n && n < MAX_MATRIX_SIZE) ? diffLerp : fastLerp)(a, b, p); } exports.levenshteinMatrix = levenshteinMatrix; - exports.editPath = editPath; + exports.patch = patch; + exports.diff = diff; exports.fastLerp = fastLerp; - exports.slowLerp = slowLerp; - exports.applyEdits = applyEdits; + exports.diffLerp = diffLerp; + exports.numericLerp = numericLerp; exports.lerp = lerp; })(typeof exports === "undefined" ? (this.stringLerp = {}) : exports);