Use Set to improve performance of union (#298)

src/parsimmon.js

@@ -97,6 +97,15 @@ function bufferExists() {
   return typeof Buffer !== "undefined";
 }
 
+function setExists() {
+  if (Parsimmon._supportsSet !== undefined) {
+    return Parsimmon._supportsSet;
+  }
+  var exists = typeof Set !== "undefined";
+  Parsimmon._supportsSet = exists;
+  return exists;
+}
+
 function ensureBuffer() {
   if (!bufferExists()) {
     throw new Error(
@@ -388,6 +397,18 @@ function makeLineColumnIndex(input, i) {
 
 // Returns the sorted set union of two arrays of strings
 function union(xs, ys) {
+  // for newer browsers/node we can improve performance by using
+  // modern JS
+  if (setExists() && Array.from) {
+    // eslint-disable-next-line no-undef
+    var set = new Set(xs);
+    for (var y = 0; y < ys.length; y++) {
+      set.add(ys[y]);
+    }
+    var arr = Array.from(set);
+    arr.sort();
+    return arr;
+  }
   var obj = {};
   for (var i = 0; i < xs.length; i++) {
     obj[xs[i]] = true;

test/.eslintrc

@@ -5,6 +5,7 @@
   },
   "globals":{
     "Parsimmon": true,
-    "assert": true
+    "assert": true,
+    "testSetScenario": true
   }
 }

test/core/alt.test.js

@@ -1,37 +1,39 @@
 "use strict";
 
-it("Parsimmon.alt", function() {
-  var toNode = function(nodeType) {
-    return function(value) {
-      return { type: nodeType, value: value };
+testSetScenario(function() {
+  it("Parsimmon.alt", function() {
+    var toNode = function(nodeType) {
+      return function(value) {
+        return { type: nodeType, value: value };
+      };
     };
-  };
 
-  var stringParser = Parsimmon.seq(
-    Parsimmon.string('"'),
-    Parsimmon.regexp(/[^"]*/),
-    Parsimmon.string('"')
-  ).map(toNode("string"));
+    var stringParser = Parsimmon.seq(
+      Parsimmon.string('"'),
+      Parsimmon.regexp(/[^"]*/),
+      Parsimmon.string('"')
+    ).map(toNode("string"));
 
-  var identifierParser = Parsimmon.regexp(/[a-zA-Z]*/).map(
-    toNode("identifier")
-  );
+    var identifierParser = Parsimmon.regexp(/[a-zA-Z]*/).map(
+      toNode("identifier")
+    );
 
-  var parser = Parsimmon.alt(stringParser, identifierParser);
+    var parser = Parsimmon.alt(stringParser, identifierParser);
 
-  assert.deepEqual(parser.parse('"a string, to be sure"').value, {
-    type: "string",
-    value: ['"', "a string, to be sure", '"']
-  });
+    assert.deepEqual(parser.parse('"a string, to be sure"').value, {
+      type: "string",
+      value: ['"', "a string, to be sure", '"']
+    });
 
-  assert.deepEqual(parser.parse("anIdentifier").value, {
-    type: "identifier",
-    value: "anIdentifier"
-  });
+    assert.deepEqual(parser.parse("anIdentifier").value, {
+      type: "identifier",
+      value: "anIdentifier"
+    });
 
-  assert.throws(function() {
-    Parsimmon.alt("not a parser");
-  });
+    assert.throws(function() {
+      Parsimmon.alt("not a parser");
+    });
 
-  assert.strictEqual(Parsimmon.alt().parse("").status, false);
+    assert.strictEqual(Parsimmon.alt().parse("").status, false);
+  });
 });

test/core/chain.test.js

@@ -1,28 +1,30 @@
 "use strict";
 
-describe("chain", function() {
-  it("asserts that a parser is returned", function() {
-    var parser1 = Parsimmon.letter.chain(function() {
-      return "not a parser";
-    });
-    assert.throws(function() {
-      parser1.parse("x");
-    });
+testSetScenario(function() {
+  describe("chain", function() {
+    it("asserts that a parser is returned", function() {
+      var parser1 = Parsimmon.letter.chain(function() {
+        return "not a parser";
+      });
+      assert.throws(function() {
+        parser1.parse("x");
+      });
 
-    assert.throws(function() {
-      Parsimmon.letter.then("x");
+      assert.throws(function() {
+        Parsimmon.letter.then("x");
+      });
     });
-  });
 
-  it("with a function that returns a parser, continues with that parser", function() {
-    var piped;
-    var parser = Parsimmon.string("x").chain(function(x) {
-      piped = x;
-      return Parsimmon.string("y");
-    });
+    it("with a function that returns a parser, continues with that parser", function() {
+      var piped;
+      var parser = Parsimmon.string("x").chain(function(x) {
+        piped = x;
+        return Parsimmon.string("y");
+      });
 
-    assert.deepEqual(parser.parse("xy"), { status: true, value: "y" });
-    assert.equal(piped, "x");
-    assert.ok(!parser.parse("x").status);
+      assert.deepEqual(parser.parse("xy"), { status: true, value: "y" });
+      assert.equal(piped, "x");
+      assert.ok(!parser.parse("x").status);
+    });
   });
 });

test/core/createLanguage.test.js

@@ -1,71 +1,73 @@
 "use strict";
 
-describe("Parsimmon.createLanguage", function() {
-  before(function() {
-    Object.prototype.NASTY = "dont extend Object.prototype please";
-  });
+testSetScenario(function() {
+  describe("Parsimmon.createLanguage", function() {
+    before(function() {
+      Object.prototype.NASTY = "dont extend Object.prototype please";
+    });
 
-  after(function() {
-    delete Object.prototype.NASTY;
-  });
+    after(function() {
+      delete Object.prototype.NASTY;
+    });
 
-  it("should return an object of parsers", function() {
-    var lang = Parsimmon.createLanguage({
-      a: function() {
-        return Parsimmon.string("a");
-      },
-      b: function() {
-        return Parsimmon.string("b");
-      }
+    it("should return an object of parsers", function() {
+      var lang = Parsimmon.createLanguage({
+        a: function() {
+          return Parsimmon.string("a");
+        },
+        b: function() {
+          return Parsimmon.string("b");
+        }
+      });
+      assert.ok(Parsimmon.isParser(lang.a));
+      assert.ok(Parsimmon.isParser(lang.b));
     });
-    assert.ok(Parsimmon.isParser(lang.a));
-    assert.ok(Parsimmon.isParser(lang.b));
-  });
 
-  it("should allow direct recursion in parsers", function() {
-    var lang = Parsimmon.createLanguage({
-      Parentheses: function(r) {
-        return Parsimmon.alt(
-          Parsimmon.string("()"),
-          Parsimmon.string("(")
-            .then(r.Parentheses)
-            .skip(Parsimmon.string(")"))
-        );
-      }
+    it("should allow direct recursion in parsers", function() {
+      var lang = Parsimmon.createLanguage({
+        Parentheses: function(r) {
+          return Parsimmon.alt(
+            Parsimmon.string("()"),
+            Parsimmon.string("(")
+              .then(r.Parentheses)
+              .skip(Parsimmon.string(")"))
+          );
+        }
+      });
+      lang.Parentheses.tryParse("(((())))");
     });
-    lang.Parentheses.tryParse("(((())))");
-  });
 
-  it("should ignore non-own properties", function() {
-    var obj = Object.create({
-      foo: function() {
-        return Parsimmon.of(1);
-      }
+    it("should ignore non-own properties", function() {
+      var obj = Object.create({
+        foo: function() {
+          return Parsimmon.of(1);
+        }
+      });
+      var lang = Parsimmon.createLanguage(obj);
+      assert.strictEqual(lang.foo, undefined);
     });
-    var lang = Parsimmon.createLanguage(obj);
-    assert.strictEqual(lang.foo, undefined);
-  });
 
-  it("should allow indirect recursion in parsers", function() {
-    var lang = Parsimmon.createLanguage({
-      Value: function(r) {
-        return Parsimmon.alt(r.Number, r.Symbol, r.List);
-      },
-      Number: function() {
-        return Parsimmon.regexp(/[0-9]+/).map(Number);
-      },
-      Symbol: function() {
-        return Parsimmon.regexp(/[a-z]+/);
-      },
-      List: function(r) {
-        return Parsimmon.string("(")
-          .then(Parsimmon.sepBy(r.Value, r._))
-          .skip(Parsimmon.string(")"));
-      },
-      _: function() {
-        return Parsimmon.optWhitespace;
-      }
+    it("should allow indirect recursion in parsers", function() {
+      var lang = Parsimmon.createLanguage({
+        Value: function(r) {
+          return Parsimmon.alt(r.Number, r.Symbol, r.List);
+        },
+        Number: function() {
+          return Parsimmon.regexp(/[0-9]+/).map(Number);
+        },
+        Symbol: function() {
+          return Parsimmon.regexp(/[a-z]+/);
+        },
+        List: function(r) {
+          return Parsimmon.string("(")
+            .then(Parsimmon.sepBy(r.Value, r._))
+            .skip(Parsimmon.string(")"));
+        },
+        _: function() {
+          return Parsimmon.optWhitespace;
+        }
+      });
+      lang.Value.tryParse("(list 1 2 foo (list nice 3 56 989 asdasdas))");
     });
-    lang.Value.tryParse("(list 1 2 foo (list nice 3 56 989 asdasdas))");
   });
 });

test/core/many.test.js

@@ -1,34 +1,36 @@
 "use strict";
 
-describe("many", function() {
-  it("simple case", function() {
-    var letters = Parsimmon.letter.many();
-    assert.deepEqual(letters.parse("x").value, ["x"]);
-    assert.deepEqual(letters.parse("xyz").value, ["x", "y", "z"]);
-    assert.deepEqual(letters.parse("").value, []);
-    assert.ok(!letters.parse("1").status);
-    assert.ok(!letters.parse("xyz1").status);
-  });
-
-  it("followed by then", function() {
-    var parser = Parsimmon.string("x")
-      .many()
-      .then(Parsimmon.string("y"));
-    assert.equal(parser.parse("y").value, "y");
-    assert.equal(parser.parse("xy").value, "y");
-    assert.equal(parser.parse("xxxxxy").value, "y");
-  });
-
-  it("throws on parsers that accept zero characters", function() {
-    var parser = Parsimmon.regexp(/a*/).many();
-    assert.throws(function() {
-      parser.parse("a");
+testSetScenario(function() {
+  describe("many", function() {
+    it("simple case", function() {
+      var letters = Parsimmon.letter.many();
+      assert.deepEqual(letters.parse("x").value, ["x"]);
+      assert.deepEqual(letters.parse("xyz").value, ["x", "y", "z"]);
+      assert.deepEqual(letters.parse("").value, []);
+      assert.ok(!letters.parse("1").status);
+      assert.ok(!letters.parse("xyz1").status);
     });
-    assert.throws(function() {
-      parser.parse("b");
+
+    it("followed by then", function() {
+      var parser = Parsimmon.string("x")
+        .many()
+        .then(Parsimmon.string("y"));
+      assert.equal(parser.parse("y").value, "y");
+      assert.equal(parser.parse("xy").value, "y");
+      assert.equal(parser.parse("xxxxxy").value, "y");
     });
-    assert.throws(function() {
-      parser.parse("");
+
+    it("throws on parsers that accept zero characters", function() {
+      var parser = Parsimmon.regexp(/a*/).many();
+      assert.throws(function() {
+        parser.parse("a");
+      });
+      assert.throws(function() {
+        parser.parse("b");
+      });
+      assert.throws(function() {
+        parser.parse("");
+      });
     });
   });
 });

test/core/map.test.js

@@ -1,19 +1,21 @@
 "use strict";
 
-describe("map", function() {
-  it("with a function, pipes the value in and uses that return value", function() {
-    var piped;
-    var parser = Parsimmon.string("x").map(function(x) {
-      piped = x;
-      return "y";
+testSetScenario(function() {
+  describe("map", function() {
+    it("with a function, pipes the value in and uses that return value", function() {
+      var piped;
+      var parser = Parsimmon.string("x").map(function(x) {
+        piped = x;
+        return "y";
+      });
+      assert.deepEqual(parser.parse("x"), { status: true, value: "y" });
+      assert.equal(piped, "x");
     });
-    assert.deepEqual(parser.parse("x"), { status: true, value: "y" });
-    assert.equal(piped, "x");
-  });
 
-  it("asserts that a function was given", function() {
-    assert.throws(function() {
-      Parsimmon.string("x").map("not a function");
+    it("asserts that a function was given", function() {
+      assert.throws(function() {
+        Parsimmon.string("x").map("not a function");
+      });
     });
   });
 });