add compiler

3 files changed, 1341 insertions, 2 deletions

diff --git a/godel/js/compiler.js b/godel/js/compiler.js
new file mode 100644
index 0000000..65ebbcd
--- /dev/null
+++ b/godel/js/compiler.js
@@ -0,0 +1,163 @@
+class StringBuilder {
+  constructor() {
+    this.stringPieces = [];
+  }
+  add(s) {
+    this.stringPieces.push(s);
+  }
+  build() {
+    return this.stringPieces.join("");
+  }
+}
+
+const compileGoto = (gotoNode, stringBuilder) => {
+  stringBuilder.add(`this.followGoto("${gotoNode.label}");\nreturn;\n`);
+};
+
+const compileConditional = (conditionalNode, stringBuilder) => {
+  const { variable, goto: gotoNode } = conditionalNode;
+
+  stringBuilder.add(`if (this.get("${variable}") != 0) {\n`);
+  compileGoto(gotoNode, stringBuilder);
+  stringBuilder.add(`}\n`);
+};
+
+const compileAssignment = (assignmentNode, stringBuilder) => {
+  const { variable, expr } = assignmentNode;
+  if (expr.opr) {
+    if (expr.opr == "+") stringBuilder.add(`this.addOne("${variable}");\n`);
+    else if (expr.opr == "-")
+      stringBuilder.add(`this.subtractOne("${variable}");\n`);
+  } else {
+    stringBuilder.add("// noop \n");
+  }
+};
+
+const compileInstruction = (instruction, stringBuilder) => {
+  if (instruction.goto) {
+    compileGoto(instruction.goto, stringBuilder);
+    return; // ignore unreachable addition to instructionPointer
+  }
+
+  if (instruction.conditional) {
+    compileConditional(instruction.conditional, stringBuilder);
+  } else if (instruction.assignment) {
+    compileAssignment(instruction.assignment, stringBuilder);
+  }
+
+  stringBuilder.add("this.instructionPointer++;\n");
+};
+
+const compile = (ast) => {
+  const stringBuilder = new StringBuilder();
+  stringBuilder.add(`
+    class Program {
+      constructor() {
+        this.variables = new Map(); // variable -> natural number val
+        this.labelInstructions = new Map(); // labels to instruction indices
+        this.instructions = new Map(); // instruction indices to procedures
+
+        this.instructions.set(0, () => this.main());
+        this.instructionPointer = 0;
+        this.variables.set("Y", 0);
+
+        // -- program-specific state init --
+        this.finalInstruction = ${
+          ast.instructions.length + 1
+        }; // instruction of the implied "exit" label
+        this.labelInstructions.set("E", this.finalInstruction); // "E" is the exit label
+      }
+
+      get(variable) {
+        if (!this.variables.has(variable)) {
+          this.variables.set(variable, 0);
+        }
+        return this.variables.get(variable);
+      }
+
+      addOne(variable) {
+        const val = this.get(variable);
+        this.variables.set(variable, val + 1);
+      }
+
+      subtractOne(variable) {
+        const val = this.get(variable);
+        this.variables.set(variable, val - 1);
+      }
+
+      followGoto(label) {
+        this.instructionPointer = this.labelInstructions.get(label);
+      }
+
+      step() {
+        if (!this.isCompleted()) {
+          const procedure = this.instructions.get(this.instructionPointer);
+          procedure();
+ 
+        }
+        return this.instructionPointer;
+      }
+
+      isCompleted() {
+        return this.instructionPointer == this.finalInstruction;
+      }
+
+      getResult() {
+        return this.variables.get("Y");
+      }
+
+      run(maxIter=50000) {
+        let iter = 0;
+        while (!this.isCompleted() && (++iter) < maxIter) this.step();
+        if (iter < maxIter) {
+          return this.getResult();
+        }
+        throw new Error("Iterations went over maxIter=(" + maxIter + "). To resolve, please ask Turing how we can tell if a program will halt during compilation.");
+      }
+
+      main() {
+`);
+
+  stringBuilder.add("// -- build label -> instruction map --\n");
+  for (let i = 0; i < ast.instructions.length; i++) {
+    const line = ast.instructions[i];
+    const instructionIdx = i + 1;
+    if (line.label) {
+      stringBuilder.add(
+        `this.instructions.set(${instructionIdx}, () => this.${line.label}());\n`,
+      );
+      stringBuilder.add(
+        `this.labelInstructions.set("${line.label}", ${instructionIdx});\n`,
+      );
+    }
+  }
+
+  stringBuilder.add("// -- compiled instructions --\n");
+  for (let i = 0; i < ast.instructions.length; i++) {
+    let instruction = ast.instructions[i];
+    const instructionIdx = i + 1;
+    if (instruction.label) {
+      stringBuilder.add(
+        `  this.followGoto("${instruction.label}");\n}\n\n${instruction.label}() {\n`,
+      );
+      stringBuilder.add(`this.instructionPointer = ${instructionIdx};\n`);
+      instruction = instruction.instruction;
+    }
+
+    compileInstruction(instruction, stringBuilder);
+  }
+
+  stringBuilder.add(`  }\n}\n`);
+  stringBuilder.add("// -- \n");
+  stringBuilder.add("const program = new Program();\n\n");
+  stringBuilder.add("// set the initial Snapshot here\n");
+  stringBuilder.add('// program.variables.set("X1", 2);\n\n');
+  stringBuilder.add(
+    "program.run(50_000); // 50_000 is the max iterations before throwing an exception\n",
+  );
+
+  return js_beautify(stringBuilder.build(), {
+    indent_size: 2,
+    wrap_line_length: 120,
+  });
+};
diff --git a/godel/js/main.js b/godel/js/main.js
index 000ce7a..bd36ef9 100644
--- a/godel/js/main.js
+++ b/godel/js/main.js
@@ -1,5 +1,121 @@
-const MESSAGES = {};
+const MESSAGES = {
+  COMPILE: "COMPILE",
+  COMPILE_RESULT: "COMPILE_RESULT",
+  EVAL: "EVAL",
+  EVAL_STATUS: "EVAL_RESULT",
+};
 
-// -- the "real" code
+// -- the "real" code --
 
 const state = new Observable();
+
+const prepareSource = (text) => text.replaceAll(/\/\/.*/g, "").trim();
+
+const main = () => {
+  let program;
+
+  state.subscribe((msg) => {
+    if (msg.type == MESSAGES.COMPILE) {
+      const { value } = msg;
+      const source = prepareSource(value);
+      try {
+        const ast = parser.parse(source);
+        const program = compile(ast);
+
+        state.notify({
+          type: MESSAGES.COMPILE_RESULT,
+          value: program,
+        });
+      } catch (e) {
+        state.notify({
+          type: MESSAGES.COMPILE_RESULT,
+          error: e.toString(),
+        });
+      }
+    }
+    if (msg.type == MESSAGES.EVAL) {
+      const source = compiledEditorEl.getValue();
+      try {
+        const result = eval(source);
+        state.notify({
+          type: MESSAGES.EVAL_RESULT,
+          value: result,
+        });
+      } catch (e) {
+        state.notify({
+          type: MESSAGES.EVAL_RESULT,
+          error: e.toString(),
+        });
+      }
+    }
+  });
+};
+main();
+
+// -- a bit of some hacky ui code --
+
+const instructionsEl = document.getElementById("instructions");
+const instructionsEditorEl = CodeMirror.fromTextArea(instructionsEl, {
+  lineNumbers: true,
+});
+
+const compileButton = document.getElementById("compile");
+const evalButton = document.getElementById("eval");
+const evalStatusEl = document.getElementById("eval_status");
+const compileStatusEl = document.getElementById("compile_status");
+const compiledEl = document.getElementById("compiled");
+const compiledEditorEl = CodeMirror.fromTextArea(compiledEl, {
+  lineNumbers: true,
+});
+state.subscribe((msg) => {
+  if (msg.type == MESSAGES.COMPILE_RESULT) {
+    evalStatusEl.classList.remove("error");
+    evalStatusEl.classList.remove("success");
+    evalStatusEl.innerHTML = "";
+
+    if (typeof msg.value !== "undefined") {
+      compiledEditorEl.setValue(msg.value);
+
+      compileStatusEl.classList.add("success");
+      compileStatusEl.classList.remove("error");
+      compileStatusEl.innerHTML = `Successful compile at ${new Date().toLocaleString()}!`;
+    } else if (msg.error) {
+      compiledEditorEl.setValue("");
+
+      compileStatusEl.classList.remove("success");
+      compileStatusEl.classList.add("error");
+      compileStatusEl.innerHTML = msg.error;
+    }
+  }
+});
+state.subscribe((msg) => {
+  if (msg.type == MESSAGES.EVAL_RESULT) {
+    if (typeof msg.value !== "undefined") {
+      evalStatusEl.classList.add("success");
+      evalStatusEl.classList.remove("error");
+      evalStatusEl.innerHTML = `Result: ${msg.value}`;
+    } else if (msg.error) {
+      evalStatusEl.classList.remove("success");
+      evalStatusEl.classList.add("error");
+      evalStatusEl.innerHTML = msg.error;
+    }
+  }
+});
+
+const urlParams = new URLSearchParams(window.location.search);
+if (urlParams.get("instructions")) {
+  editorEl.setValue(atob(urlParams.get("instructions")));
+}
+
+compileButton.addEventListener("click", () => {
+  state.notify({
+    type: MESSAGES.COMPILE,
+    value: instructionsEditorEl.getValue(),
+  });
+});
+
+evalButton.addEventListener("click", () => {
+  state.notify({
+    type: MESSAGES.EVAL,
+  });
+});
diff --git a/godel/js/parser.js b/godel/js/parser.js
new file mode 100644
index 0000000..c582a28
--- /dev/null
+++ b/godel/js/parser.js
@@ -0,0 +1,1060 @@
+parser = /*
+ * Generated by PEG.js 0.10.0.
+ *
+ * http://pegjs.org/
+ */
+(function() {
+  "use strict";
+
+  function peg$subclass(child, parent) {
+    function ctor() { this.constructor = child; }
+    ctor.prototype = parent.prototype;
+    child.prototype = new ctor();
+  }
+
+  function peg$SyntaxError(message, expected, found, location) {
+    this.message  = message;
+    this.expected = expected;
+    this.found    = found;
+    this.location = location;
+    this.name     = "SyntaxError";
+
+    if (typeof Error.captureStackTrace === "function") {
+      Error.captureStackTrace(this, peg$SyntaxError);
+    }
+  }
+
+  peg$subclass(peg$SyntaxError, Error);
+
+  peg$SyntaxError.buildMessage = function(expected, found) {
+    var DESCRIBE_EXPECTATION_FNS = {
+          literal: function(expectation) {
+            return "\"" + literalEscape(expectation.text) + "\"";
+          },
+
+          "class": function(expectation) {
+            var escapedParts = "",
+                i;
+
+            for (i = 0; i < expectation.parts.length; i++) {
+              escapedParts += expectation.parts[i] instanceof Array
+                ? classEscape(expectation.parts[i][0]) + "-" + classEscape(expectation.parts[i][1])
+                : classEscape(expectation.parts[i]);
+            }
+
+            return "[" + (expectation.inverted ? "^" : "") + escapedParts + "]";
+          },
+
+          any: function(expectation) {
+            return "any character";
+          },
+
+          end: function(expectation) {
+            return "end of input";
+          },
+
+          other: function(expectation) {
+            return expectation.description;
+          }
+        };
+
+    function hex(ch) {
+      return ch.charCodeAt(0).toString(16).toUpperCase();
+    }
+
+    function literalEscape(s) {
+      return s
+        .replace(/\\/g, '\\\\')
+        .replace(/"/g,  '\\"')
+        .replace(/\0/g, '\\0')
+        .replace(/\t/g, '\\t')
+        .replace(/\n/g, '\\n')
+        .replace(/\r/g, '\\r')
+        .replace(/[\x00-\x0F]/g,          function(ch) { return '\\x0' + hex(ch); })
+        .replace(/[\x10-\x1F\x7F-\x9F]/g, function(ch) { return '\\x'  + hex(ch); });
+    }
+
+    function classEscape(s) {
+      return s
+        .replace(/\\/g, '\\\\')
+        .replace(/\]/g, '\\]')
+        .replace(/\^/g, '\\^')
+        .replace(/-/g,  '\\-')
+        .replace(/\0/g, '\\0')
+        .replace(/\t/g, '\\t')
+        .replace(/\n/g, '\\n')
+        .replace(/\r/g, '\\r')
+        .replace(/[\x00-\x0F]/g,          function(ch) { return '\\x0' + hex(ch); })
+        .replace(/[\x10-\x1F\x7F-\x9F]/g, function(ch) { return '\\x'  + hex(ch); });
+    }
+
+    function describeExpectation(expectation) {
+      return DESCRIBE_EXPECTATION_FNS[expectation.type](expectation);
+    }
+
+    function describeExpected(expected) {
+      var descriptions = new Array(expected.length),
+          i, j;
+
+      for (i = 0; i < expected.length; i++) {
+        descriptions[i] = describeExpectation(expected[i]);
+      }
+
+      descriptions.sort();
+
+      if (descriptions.length > 0) {
+        for (i = 1, j = 1; i < descriptions.length; i++) {
+          if (descriptions[i - 1] !== descriptions[i]) {
+            descriptions[j] = descriptions[i];
+            j++;
+          }
+        }
+        descriptions.length = j;
+      }
+
+      switch (descriptions.length) {
+        case 1:
+          return descriptions[0];
+
+        case 2:
+          return descriptions[0] + " or " + descriptions[1];
+
+        default:
+          return descriptions.slice(0, -1).join(", ")
+            + ", or "
+            + descriptions[descriptions.length - 1];
+      }
+    }
+
+    function describeFound(found) {
+      return found ? "\"" + literalEscape(found) + "\"" : "end of input";
+    }
+
+    return "Expected " + describeExpected(expected) + " but " + describeFound(found) + " found.";
+  };
+
+  function peg$parse(input, options) {
+    options = options !== void 0 ? options : {};
+
+    var peg$FAILED = {},
+
+        peg$startRuleFunctions = { Program: peg$parseProgram },
+        peg$startRuleFunction  = peg$parseProgram,
+
+        peg$c0 = /^[\n]/,
+        peg$c1 = peg$classExpectation(["\n"], false, false),
+        peg$c2 = function(lines) {
+          return { instructions: lines.filter((line) => typeof line !== "string" || line.trim() != "") };
+        },
+        peg$c3 = function(instruction) {
+          return instruction;
+        },
+        peg$c4 = function(label, instruction) {
+          return { label, instruction };
+        },
+        peg$c5 = "[",
+        peg$c6 = peg$literalExpectation("[", false),
+        peg$c7 = "]",
+        peg$c8 = peg$literalExpectation("]", false),
+        peg$c9 = function(label) {
+          return label;
+        },
+        peg$c10 = function(conditional) { return { conditional }; },
+        peg$c11 = function(assignment) { return { assignment }; },
+        peg$c12 = function(goto) { return { goto }; },
+        peg$c13 = function(label) {
+          return { label };
+        },
+        peg$c14 = "IF",
+        peg$c15 = peg$literalExpectation("IF", false),
+        peg$c16 = "!=",
+        peg$c17 = peg$literalExpectation("!=", false),
+        peg$c18 = "0",
+        peg$c19 = peg$literalExpectation("0", false),
+        peg$c20 = function(variable, goto) {
+          return { variable, goto };
+        },
+        peg$c21 = "<-",
+        peg$c22 = peg$literalExpectation("<-", false),
+        peg$c23 = function(variable, expr) {
+          if (expr.left != variable) {
+            error("left hand variable must match right hand");
+          }
+          return { variable, expr };
+        },
+        peg$c24 = "1",
+        peg$c25 = peg$literalExpectation("1", false),
+        peg$c26 = function(left, opr) {
+          return { left, opr };
+        },
+        peg$c27 = function(left) {
+          return { left };
+        },
+        peg$c28 = "Y",
+        peg$c29 = peg$literalExpectation("Y", false),
+        peg$c30 = function(symbol) { return symbol },
+        peg$c31 = "X",
+        peg$c32 = peg$literalExpectation("X", false),
+        peg$c33 = "Z",
+        peg$c34 = peg$literalExpectation("Z", false),
+        peg$c35 = function(symbol, ind) {
+          return symbol + ind;
+        },
+        peg$c36 = "GOTO",
+        peg$c37 = peg$literalExpectation("GOTO", false),
+        peg$c38 = "+",
+        peg$c39 = peg$literalExpectation("+", false),
+        peg$c40 = "-",
+        peg$c41 = peg$literalExpectation("-", false),
+        peg$c42 = /^[A-E]/,
+        peg$c43 = peg$classExpectation([["A", "E"]], false, false),
+        peg$c44 = "E",
+        peg$c45 = peg$literalExpectation("E", false),
+        peg$c46 = peg$otherExpectation("integer"),
+        peg$c47 = /^[0-9]/,
+        peg$c48 = peg$classExpectation([["0", "9"]], false, false),
+        peg$c49 = function() { return parseInt(text(), 10); },
+        peg$c50 = peg$otherExpectation("whitespace"),
+        peg$c51 = /^[ \t]/,
+        peg$c52 = peg$classExpectation([" ", "\t"], false, false),
+        peg$c53 = function() {  },
+
+        peg$currPos          = 0,
+        peg$savedPos         = 0,
+        peg$posDetailsCache  = [{ line: 1, column: 1 }],
+        peg$maxFailPos       = 0,
+        peg$maxFailExpected  = [],
+        peg$silentFails      = 0,
+
+        peg$result;
+
+    if ("startRule" in options) {
+      if (!(options.startRule in peg$startRuleFunctions)) {
+        throw new Error("Can't start parsing from rule \"" + options.startRule + "\".");
+      }
+
+      peg$startRuleFunction = peg$startRuleFunctions[options.startRule];
+    }
+
+    function text() {
+      return input.substring(peg$savedPos, peg$currPos);
+    }
+
+    function location() {
+      return peg$computeLocation(peg$savedPos, peg$currPos);
+    }
+
+    function expected(description, location) {
+      location = location !== void 0 ? location : peg$computeLocation(peg$savedPos, peg$currPos)
+
+      throw peg$buildStructuredError(
+        [peg$otherExpectation(description)],
+        input.substring(peg$savedPos, peg$currPos),
+        location
+      );
+    }
+
+    function error(message, location) {
+      location = location !== void 0 ? location : peg$computeLocation(peg$savedPos, peg$currPos)
+
+      throw peg$buildSimpleError(message, location);
+    }
+
+    function peg$literalExpectation(text, ignoreCase) {
+      return { type: "literal", text: text, ignoreCase: ignoreCase };
+    }
+
+    function peg$classExpectation(parts, inverted, ignoreCase) {
+      return { type: "class", parts: parts, inverted: inverted, ignoreCase: ignoreCase };
+    }
+
+    function peg$anyExpectation() {
+      return { type: "any" };
+    }
+
+    function peg$endExpectation() {
+      return { type: "end" };
+    }
+
+    function peg$otherExpectation(description) {
+      return { type: "other", description: description };
+    }
+
+    function peg$computePosDetails(pos) {
+      var details = peg$posDetailsCache[pos], p;
+
+      if (details) {
+        return details;
+      } else {
+        p = pos - 1;
+        while (!peg$posDetailsCache[p]) {
+          p--;
+        }
+
+        details = peg$posDetailsCache[p];
+        details = {
+          line:   details.line,
+          column: details.column
+        };
+
+        while (p < pos) {
+          if (input.charCodeAt(p) === 10) {
+            details.line++;
+            details.column = 1;
+          } else {
+            details.column++;
+          }
+
+          p++;
+        }
+
+        peg$posDetailsCache[pos] = details;
+        return details;
+      }
+    }
+
+    function peg$computeLocation(startPos, endPos) {
+      var startPosDetails = peg$computePosDetails(startPos),
+          endPosDetails   = peg$computePosDetails(endPos);
+
+      return {
+        start: {
+          offset: startPos,
+          line:   startPosDetails.line,
+          column: startPosDetails.column
+        },
+        end: {
+          offset: endPos,
+          line:   endPosDetails.line,
+          column: endPosDetails.column
+        }
+      };
+    }
+
+    function peg$fail(expected) {
+      if (peg$currPos < peg$maxFailPos) { return; }
+
+      if (peg$currPos > peg$maxFailPos) {
+        peg$maxFailPos = peg$currPos;
+        peg$maxFailExpected = [];
+      }
+
+      peg$maxFailExpected.push(expected);
+    }
+
+    function peg$buildSimpleError(message, location) {
+      return new peg$SyntaxError(message, null, null, location);
+    }
+
+    function peg$buildStructuredError(expected, found, location) {
+      return new peg$SyntaxError(
+        peg$SyntaxError.buildMessage(expected, found),
+        expected,
+        found,
+        location
+      );
+    }
+
+    function peg$parseProgram() {
+      var s0, s1, s2;
+
+      s0 = peg$currPos;
+      s1 = [];
+      s2 = peg$parseLine();
+      if (s2 === peg$FAILED) {
+        s2 = peg$parse_();
+        if (s2 === peg$FAILED) {
+          if (peg$c0.test(input.charAt(peg$currPos))) {
+            s2 = input.charAt(peg$currPos);
+            peg$currPos++;
+          } else {
+            s2 = peg$FAILED;
+            if (peg$silentFails === 0) { peg$fail(peg$c1); }
+          }
+        }
+      }
+      while (s2 !== peg$FAILED) {
+        s1.push(s2);
+        s2 = peg$parseLine();
+        if (s2 === peg$FAILED) {
+          s2 = peg$parse_();
+          if (s2 === peg$FAILED) {
+            if (peg$c0.test(input.charAt(peg$currPos))) {
+              s2 = input.charAt(peg$currPos);
+              peg$currPos++;
+            } else {
+              s2 = peg$FAILED;
+              if (peg$silentFails === 0) { peg$fail(peg$c1); }
+            }
+          }
+        }
+      }
+      if (s1 !== peg$FAILED) {
+        peg$savedPos = s0;
+        s1 = peg$c2(s1);
+      }
+      s0 = s1;
+
+      return s0;
+    }
+
+    function peg$parseLine() {
+      var s0, s1, s2, s3, s4;
+
+      s0 = peg$currPos;
+      s1 = peg$parse_();
+      if (s1 === peg$FAILED) {
+        s1 = null;
+      }
+      if (s1 !== peg$FAILED) {
+        s2 = peg$parseLabeledInstruction();
+        if (s2 === peg$FAILED) {
+          s2 = peg$parseInstruction();
+        }
+        if (s2 !== peg$FAILED) {
+          s3 = peg$parse_();
+          if (s3 === peg$FAILED) {
+            s3 = null;
+          }
+          if (s3 !== peg$FAILED) {
+            if (peg$c0.test(input.charAt(peg$currPos))) {
+              s4 = input.charAt(peg$currPos);
+              peg$currPos++;
+            } else {
+              s4 = peg$FAILED;
+              if (peg$silentFails === 0) { peg$fail(peg$c1); }
+            }
+            if (s4 === peg$FAILED) {
+              s4 = null;
+            }
+            if (s4 !== peg$FAILED) {
+              peg$savedPos = s0;
+              s1 = peg$c3(s2);
+              s0 = s1;
+            } else {
+              peg$currPos = s0;
+              s0 = peg$FAILED;
+            }
+          } else {
+            peg$currPos = s0;
+            s0 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s0;
+          s0 = peg$FAILED;
+        }
+      } else {
+        peg$currPos = s0;
+        s0 = peg$FAILED;
+      }
+
+      return s0;
+    }
+
+    function peg$parseLabeledInstruction() {
+      var s0, s1, s2, s3;
+
+      s0 = peg$currPos;
+      s1 = peg$parseLabel();
+      if (s1 !== peg$FAILED) {
+        s2 = peg$parse_();
+        if (s2 !== peg$FAILED) {
+          s3 = peg$parseInstruction();
+          if (s3 !== peg$FAILED) {
+            peg$savedPos = s0;
+            s1 = peg$c4(s1, s3);
+            s0 = s1;
+          } else {
+            peg$currPos = s0;
+            s0 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s0;
+          s0 = peg$FAILED;
+        }
+      } else {
+        peg$currPos = s0;
+        s0 = peg$FAILED;
+      }
+
+      return s0;
+    }
+
+    function peg$parseLabel() {
+      var s0, s1, s2, s3, s4, s5;
+
+      s0 = peg$currPos;
+      if (input.charCodeAt(peg$currPos) === 91) {
+        s1 = peg$c5;
+        peg$currPos++;
+      } else {
+        s1 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c6); }
+      }
+      if (s1 !== peg$FAILED) {
+        s2 = peg$parse_();
+        if (s2 === peg$FAILED) {
+          s2 = null;
+        }
+        if (s2 !== peg$FAILED) {
+          s3 = peg$parseLABEL_V();
+          if (s3 !== peg$FAILED) {
+            s4 = peg$parse_();
+            if (s4 === peg$FAILED) {
+              s4 = null;
+            }
+            if (s4 !== peg$FAILED) {
+              if (input.charCodeAt(peg$currPos) === 93) {
+                s5 = peg$c7;
+                peg$currPos++;
+              } else {
+                s5 = peg$FAILED;
+                if (peg$silentFails === 0) { peg$fail(peg$c8); }
+              }
+              if (s5 !== peg$FAILED) {
+                peg$savedPos = s0;
+                s1 = peg$c9(s3);
+                s0 = s1;
+              } else {
+                peg$currPos = s0;
+                s0 = peg$FAILED;
+              }
+            } else {
+              peg$currPos = s0;
+              s0 = peg$FAILED;
+            }
+          } else {
+            peg$currPos = s0;
+            s0 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s0;
+          s0 = peg$FAILED;
+        }
+      } else {
+        peg$currPos = s0;
+        s0 = peg$FAILED;
+      }
+
+      return s0;
+    }
+
+    function peg$parseInstruction() {
+      var s0, s1;
+
+      s0 = peg$currPos;
+      s1 = peg$parseConditional();
+      if (s1 !== peg$FAILED) {
+        peg$savedPos = s0;
+        s1 = peg$c10(s1);
+      }
+      s0 = s1;
+      if (s0 === peg$FAILED) {
+        s0 = peg$currPos;
+        s1 = peg$parseAssignment();
+        if (s1 !== peg$FAILED) {
+          peg$savedPos = s0;
+          s1 = peg$c11(s1);
+        }
+        s0 = s1;
+        if (s0 === peg$FAILED) {
+          s0 = peg$currPos;
+          s1 = peg$parseGoto();
+          if (s1 !== peg$FAILED) {
+            peg$savedPos = s0;
+            s1 = peg$c12(s1);
+          }
+          s0 = s1;
+        }
+      }
+
+      return s0;
+    }
+
+    function peg$parseGoto() {
+      var s0, s1, s2, s3;
+
+      s0 = peg$currPos;
+      s1 = peg$parseGOTO();
+      if (s1 !== peg$FAILED) {
+        s2 = peg$parse_();
+        if (s2 !== peg$FAILED) {
+          s3 = peg$parseLABEL_V();
+          if (s3 !== peg$FAILED) {
+            peg$savedPos = s0;
+            s1 = peg$c13(s3);
+            s0 = s1;
+          } else {
+            peg$currPos = s0;
+            s0 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s0;
+          s0 = peg$FAILED;
+        }
+      } else {
+        peg$currPos = s0;
+        s0 = peg$FAILED;
+      }
+
+      return s0;
+    }
+
+    function peg$parseConditional() {
+      var s0, s1, s2, s3, s4, s5, s6, s7, s8, s9;
+
+      s0 = peg$currPos;
+      if (input.substr(peg$currPos, 2) === peg$c14) {
+        s1 = peg$c14;
+        peg$currPos += 2;
+      } else {
+        s1 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c15); }
+      }
+      if (s1 !== peg$FAILED) {
+        s2 = peg$parse_();
+        if (s2 !== peg$FAILED) {
+          s3 = peg$parseVAR();
+          if (s3 !== peg$FAILED) {
+            s4 = peg$parse_();
+            if (s4 === peg$FAILED) {
+              s4 = null;
+            }
+            if (s4 !== peg$FAILED) {
+              if (input.substr(peg$currPos, 2) === peg$c16) {
+                s5 = peg$c16;
+                peg$currPos += 2;
+              } else {
+                s5 = peg$FAILED;
+                if (peg$silentFails === 0) { peg$fail(peg$c17); }
+              }
+              if (s5 !== peg$FAILED) {
+                s6 = peg$parse_();
+                if (s6 === peg$FAILED) {
+                  s6 = null;
+                }
+                if (s6 !== peg$FAILED) {
+                  if (input.charCodeAt(peg$currPos) === 48) {
+                    s7 = peg$c18;
+                    peg$currPos++;
+                  } else {
+                    s7 = peg$FAILED;
+                    if (peg$silentFails === 0) { peg$fail(peg$c19); }
+                  }
+                  if (s7 !== peg$FAILED) {
+                    s8 = peg$parse_();
+                    if (s8 !== peg$FAILED) {
+                      s9 = peg$parseGoto();
+                      if (s9 !== peg$FAILED) {
+                        peg$savedPos = s0;
+                        s1 = peg$c20(s3, s9);
+                        s0 = s1;
+                      } else {
+                        peg$currPos = s0;
+                        s0 = peg$FAILED;
+                      }
+                    } else {
+                      peg$currPos = s0;
+                      s0 = peg$FAILED;
+                    }
+                  } else {
+                    peg$currPos = s0;
+                    s0 = peg$FAILED;
+                  }
+                } else {
+                  peg$currPos = s0;
+                  s0 = peg$FAILED;
+                }
+              } else {
+                peg$currPos = s0;
+                s0 = peg$FAILED;
+              }
+            } else {
+              peg$currPos = s0;
+              s0 = peg$FAILED;
+            }
+          } else {
+            peg$currPos = s0;
+            s0 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s0;
+          s0 = peg$FAILED;
+        }
+      } else {
+        peg$currPos = s0;
+        s0 = peg$FAILED;
+      }
+
+      return s0;
+    }
+
+    function peg$parseAssignment() {
+      var s0, s1, s2, s3, s4, s5;
+
+      s0 = peg$currPos;
+      s1 = peg$parseVAR();
+      if (s1 !== peg$FAILED) {
+        s2 = peg$parse_();
+        if (s2 !== peg$FAILED) {
+          if (input.substr(peg$currPos, 2) === peg$c21) {
+            s3 = peg$c21;
+            peg$currPos += 2;
+          } else {
+            s3 = peg$FAILED;
+            if (peg$silentFails === 0) { peg$fail(peg$c22); }
+          }
+          if (s3 !== peg$FAILED) {
+            s4 = peg$parse_();
+            if (s4 !== peg$FAILED) {
+              s5 = peg$parseExpression();
+              if (s5 !== peg$FAILED) {
+                peg$savedPos = s0;
+                s1 = peg$c23(s1, s5);
+                s0 = s1;
+              } else {
+                peg$currPos = s0;
+                s0 = peg$FAILED;
+              }
+            } else {
+              peg$currPos = s0;
+              s0 = peg$FAILED;
+            }
+          } else {
+            peg$currPos = s0;
+            s0 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s0;
+          s0 = peg$FAILED;
+        }
+      } else {
+        peg$currPos = s0;
+        s0 = peg$FAILED;
+      }
+
+      return s0;
+    }
+
+    function peg$parseExpression() {
+      var s0, s1, s2, s3, s4, s5;
+
+      s0 = peg$currPos;
+      s1 = peg$parseVAR();
+      if (s1 !== peg$FAILED) {
+        s2 = peg$parse_();
+        if (s2 !== peg$FAILED) {
+          s3 = peg$parseOPERATION();
+          if (s3 !== peg$FAILED) {
+            s4 = peg$parse_();
+            if (s4 !== peg$FAILED) {
+              if (input.charCodeAt(peg$currPos) === 49) {
+                s5 = peg$c24;
+                peg$currPos++;
+              } else {
+                s5 = peg$FAILED;
+                if (peg$silentFails === 0) { peg$fail(peg$c25); }
+              }
+              if (s5 !== peg$FAILED) {
+                peg$savedPos = s0;
+                s1 = peg$c26(s1, s3);
+                s0 = s1;
+              } else {
+                peg$currPos = s0;
+                s0 = peg$FAILED;
+              }
+            } else {
+              peg$currPos = s0;
+              s0 = peg$FAILED;
+            }
+          } else {
+            peg$currPos = s0;
+            s0 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s0;
+          s0 = peg$FAILED;
+        }
+      } else {
+        peg$currPos = s0;
+        s0 = peg$FAILED;
+      }
+      if (s0 === peg$FAILED) {
+        s0 = peg$currPos;
+        s1 = peg$parseVAR();
+        if (s1 !== peg$FAILED) {
+          peg$savedPos = s0;
+          s1 = peg$c27(s1);
+        }
+        s0 = s1;
+      }
+
+      return s0;
+    }
+
+    function peg$parseVAR() {
+      var s0, s1, s2, s3;
+
+      s0 = peg$currPos;
+      if (input.charCodeAt(peg$currPos) === 89) {
+        s1 = peg$c28;
+        peg$currPos++;
+      } else {
+        s1 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c29); }
+      }
+      if (s1 !== peg$FAILED) {
+        peg$savedPos = s0;
+        s1 = peg$c30(s1);
+      }
+      s0 = s1;
+      if (s0 === peg$FAILED) {
+        s0 = peg$currPos;
+        if (input.charCodeAt(peg$currPos) === 88) {
+          s1 = peg$c31;
+          peg$currPos++;
+        } else {
+          s1 = peg$FAILED;
+          if (peg$silentFails === 0) { peg$fail(peg$c32); }
+        }
+        if (s1 === peg$FAILED) {
+          if (input.charCodeAt(peg$currPos) === 90) {
+            s1 = peg$c33;
+            peg$currPos++;
+          } else {
+            s1 = peg$FAILED;
+            if (peg$silentFails === 0) { peg$fail(peg$c34); }
+          }
+        }
+        if (s1 !== peg$FAILED) {
+          s2 = [];
+          s3 = peg$parseInteger();
+          if (s3 !== peg$FAILED) {
+            while (s3 !== peg$FAILED) {
+              s2.push(s3);
+              s3 = peg$parseInteger();
+            }
+          } else {
+            s2 = peg$FAILED;
+          }
+          if (s2 !== peg$FAILED) {
+            peg$savedPos = s0;
+            s1 = peg$c35(s1, s2);
+            s0 = s1;
+          } else {
+            peg$currPos = s0;
+            s0 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s0;
+          s0 = peg$FAILED;
+        }
+      }
+
+      return s0;
+    }
+
+    function peg$parseGOTO() {
+      var s0;
+
+      if (input.substr(peg$currPos, 4) === peg$c36) {
+        s0 = peg$c36;
+        peg$currPos += 4;
+      } else {
+        s0 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c37); }
+      }
+
+      return s0;
+    }
+
+    function peg$parseOPERATION() {
+      var s0;
+
+      if (input.charCodeAt(peg$currPos) === 43) {
+        s0 = peg$c38;
+        peg$currPos++;
+      } else {
+        s0 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c39); }
+      }
+      if (s0 === peg$FAILED) {
+        if (input.charCodeAt(peg$currPos) === 45) {
+          s0 = peg$c40;
+          peg$currPos++;
+        } else {
+          s0 = peg$FAILED;
+          if (peg$silentFails === 0) { peg$fail(peg$c41); }
+        }
+      }
+
+      return s0;
+    }
+
+    function peg$parseLABEL_V() {
+      var s0, s1, s2, s3;
+
+      s0 = peg$currPos;
+      s1 = peg$parseEND_LABEL();
+      if (s1 !== peg$FAILED) {
+        peg$savedPos = s0;
+        s1 = peg$c30(s1);
+      }
+      s0 = s1;
+      if (s0 === peg$FAILED) {
+        s0 = peg$currPos;
+        if (peg$c42.test(input.charAt(peg$currPos))) {
+          s1 = input.charAt(peg$currPos);
+          peg$currPos++;
+        } else {
+          s1 = peg$FAILED;
+          if (peg$silentFails === 0) { peg$fail(peg$c43); }
+        }
+        if (s1 !== peg$FAILED) {
+          s2 = [];
+          s3 = peg$parseInteger();
+          if (s3 !== peg$FAILED) {
+            while (s3 !== peg$FAILED) {
+              s2.push(s3);
+              s3 = peg$parseInteger();
+            }
+          } else {
+            s2 = peg$FAILED;
+          }
+          if (s2 !== peg$FAILED) {
+            peg$savedPos = s0;
+            s1 = peg$c35(s1, s2);
+            s0 = s1;
+          } else {
+            peg$currPos = s0;
+            s0 = peg$FAILED;
+          }
+        } else {
+          peg$currPos = s0;
+          s0 = peg$FAILED;
+        }
+      }
+
+      return s0;
+    }
+
+    function peg$parseEND_LABEL() {
+      var s0;
+
+      if (input.charCodeAt(peg$currPos) === 69) {
+        s0 = peg$c44;
+        peg$currPos++;
+      } else {
+        s0 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c45); }
+      }
+
+      return s0;
+    }
+
+    function peg$parseInteger() {
+      var s0, s1, s2;
+
+      peg$silentFails++;
+      s0 = peg$currPos;
+      s1 = [];
+      if (peg$c47.test(input.charAt(peg$currPos))) {
+        s2 = input.charAt(peg$currPos);
+        peg$currPos++;
+      } else {
+        s2 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c48); }
+      }
+      if (s2 !== peg$FAILED) {
+        while (s2 !== peg$FAILED) {
+          s1.push(s2);
+          if (peg$c47.test(input.charAt(peg$currPos))) {
+            s2 = input.charAt(peg$currPos);
+            peg$currPos++;
+          } else {
+            s2 = peg$FAILED;
+            if (peg$silentFails === 0) { peg$fail(peg$c48); }
+          }
+        }
+      } else {
+        s1 = peg$FAILED;
+      }
+      if (s1 !== peg$FAILED) {
+        peg$savedPos = s0;
+        s1 = peg$c49();
+      }
+      s0 = s1;
+      peg$silentFails--;
+      if (s0 === peg$FAILED) {
+        s1 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c46); }
+      }
+
+      return s0;
+    }
+
+    function peg$parse_() {
+      var s0, s1, s2;
+
+      peg$silentFails++;
+      s0 = peg$currPos;
+      s1 = [];
+      if (peg$c51.test(input.charAt(peg$currPos))) {
+        s2 = input.charAt(peg$currPos);
+        peg$currPos++;
+      } else {
+        s2 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c52); }
+      }
+      if (s2 !== peg$FAILED) {
+        while (s2 !== peg$FAILED) {
+          s1.push(s2);
+          if (peg$c51.test(input.charAt(peg$currPos))) {
+            s2 = input.charAt(peg$currPos);
+            peg$currPos++;
+          } else {
+            s2 = peg$FAILED;
+            if (peg$silentFails === 0) { peg$fail(peg$c52); }
+          }
+        }
+      } else {
+        s1 = peg$FAILED;
+      }
+      if (s1 !== peg$FAILED) {
+        peg$savedPos = s0;
+        s1 = peg$c53();
+      }
+      s0 = s1;
+      peg$silentFails--;
+      if (s0 === peg$FAILED) {
+        s1 = peg$FAILED;
+        if (peg$silentFails === 0) { peg$fail(peg$c50); }
+      }
+
+      return s0;
+    }
+
+    peg$result = peg$startRuleFunction();
+
+    if (peg$result !== peg$FAILED && peg$currPos === input.length) {
+      return peg$result;
+    } else {
+      if (peg$result !== peg$FAILED && peg$currPos < input.length) {
+        peg$fail(peg$endExpectation());
+      }
+
+      throw peg$buildStructuredError(
+        peg$maxFailExpected,
+        peg$maxFailPos < input.length ? input.charAt(peg$maxFailPos) : null,
+        peg$maxFailPos < input.length
+          ? peg$computeLocation(peg$maxFailPos, peg$maxFailPos + 1)
+          : peg$computeLocation(peg$maxFailPos, peg$maxFailPos)
+      );
+    }
+  }
+
+  return {
+    SyntaxError: peg$SyntaxError,
+    parse:       peg$parse
+  };
+})();