Add while and until loops

Author: jamiehale

examples/tests/loops.tab

@@ -0,0 +1,23 @@
+x = 1
+while (x == 2) {
+  assert(false)
+}
+
+x = 1
+y = while (x < 10) {
+  x += 1
+}
+assert(x == 10)
+assert(y == 10)
+
+x = 1
+until (x == 1) {
+  assert(false)
+}
+
+x = 1
+y = until (x == 10) {
+  x += 1
+}
+assert(x == 10)
+assert(y == 10)

src/expressions/assignment.js

@@ -23,21 +23,32 @@ import { expressionTypes } from './types';
 const operators = {
   '=': (context, leftHandSideValue, leftValue, value) => {
     leftHandSideValue.assignFrom(context, value);
+    return value;
   },
   '+=': (context, leftHandSideValue, leftValue, value) => {
-    leftHandSideValue.assignFrom(context, leftValue.add(context, value));
+    const result = leftValue.add(context, value);
+    leftHandSideValue.assignFrom(context, result);
+    return result;
   },
   '-=': (context, leftHandSideValue, leftValue, value) => {
-    leftHandSideValue.assignFrom(context, leftValue.subtract(context, value));
+    const result = leftValue.subtract(context, value);
+    leftHandSideValue.assignFrom(context, result);
+    return result;
   },
   '*=': (context, leftHandSideValue, leftValue, value) => {
-    leftHandSideValue.assignFrom(context, leftValue.multiplyBy(context, value));
+    const result = leftValue.multiplyBy(context, value);
+    leftHandSideValue.assignFrom(context, result);
+    return result;
   },
   '/=': (context, leftHandSideValue, leftValue, value) => {
-    leftHandSideValue.assignFrom(context, leftValue.divideBy(context, value));
+    const result = leftValue.divideBy(context, value);
+    leftHandSideValue.assignFrom(context, result);
+    return result;
   },
   '%=': (context, leftHandSideValue, leftValue, value) => {
-    leftHandSideValue.assignFrom(context, leftValue.modulo(context, value));
+    const result = leftValue.modulo(context, value);
+    leftHandSideValue.assignFrom(context, result);
+    return result;
   },
 };
 
@@ -50,11 +61,9 @@ const evaluate = (location, leftHandSideExpression, operator, valueExpression) =
   const value = await valueExpression.evaluate(context);
   if (operators[operator]) {
     const leftValue = (operator === '=') ? undefined : await leftHandSideExpression.evaluate(context);
-    operators[operator](context, leftHandSideValue, leftValue, value);
-  } else {
-    throwRuntimeError(`Unknown operator ${operator}`, context);
+    return operators[operator](context, leftHandSideValue, leftValue, value);
   }
-  return value;
+  throwRuntimeError(`Unknown operator ${operator}`, context);
 };
 
 export const createAssignmentExpression = (location, leftHandSideExpression, operator, valueExpression) => {

src/expressions/types.js

@@ -37,7 +37,9 @@ export const expressionTypes = {
   TEMPLATE_STRING: Symbol('TEMPLATE_STRING'),
   UNARY: Symbol('UNARY'),
   UNDEFINED: Symbol('UNDEFINED'),
+  UNTIL: Symbol('UNTIL'),
   VARIABLE: Symbol('VARIABLE'),
+  WHILE: Symbol('WHILE'),
 };
 
 export const expressionTypeName = type => {
@@ -84,8 +86,12 @@ export const expressionTypeName = type => {
       return 'unary';
     case expressionTypes.UNDEFINED:
       return 'undefined';
+    case expressionTypes.UNTIL:
+      return 'until';
     case expressionTypes.VARIABLE:
       return 'variable';
+    case expressionTypes.WHILE:
+      return 'while';
     default:
       return '<TYPE UNSET>';
   }

src/expressions/until.js

@@ -0,0 +1,39 @@
+// Copyright 2017 Jamie Hale
+//
+// This file is part of Tablescript.js.
+//
+// Tablescript.js is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Tablescript.js is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Tablescript.js. If not, see <http://www.gnu.org/licenses/>.
+
+import { createExpression } from './default';
+import { expressionTypes } from './types';
+
+const evaluate = (location, condition, loopBlock) => async context => {
+  context.setLocation(location);
+  let expressionValue = await condition.evaluate(context);
+  let result = context.factory.createUndefined();
+  while (!expressionValue.asNativeBoolean(context)) {
+    result = await loopBlock.evaluate(context);
+    expressionValue = await condition.evaluate(context);
+  }
+  return result;
+};
+
+export const createUntilExpression = (
+  location,
+  condition,
+  loopBlock
+) => createExpression(
+  expressionTypes.UNTIL,
+  evaluate(location, condition, loopBlock)
+);

src/expressions/while.js

@@ -0,0 +1,39 @@
+// Copyright 2017 Jamie Hale
+//
+// This file is part of Tablescript.js.
+//
+// Tablescript.js is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Tablescript.js is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Tablescript.js. If not, see <http://www.gnu.org/licenses/>.
+
+import { createExpression } from './default';
+import { expressionTypes } from './types';
+
+const evaluate = (location, condition, loopBlock) => async context => {
+  context.setLocation(location);
+  let expressionValue = await condition.evaluate(context);
+  let result = context.factory.createUndefined();
+  while (expressionValue.asNativeBoolean(context)) {
+    result = await loopBlock.evaluate(context);
+    expressionValue = await condition.evaluate(context);
+  }
+  return result;
+};
+
+export const createWhileExpression = (
+  location,
+  condition,
+  loopBlock
+) => createExpression(
+  expressionTypes.WHILE,
+  evaluate(location, condition, loopBlock)
+);

src/grammar/tablescript.pegjs

@@ -51,6 +51,8 @@
   const { createTemplateStringLiteral } = require('../expressions/template-string-literal');
   const { createUndefinedLiteral } = require('../expressions/undefined-literal');
   const { createIfExpression } = require('../expressions/if');
+  const { createWhileExpression } = require('../expressions/while');
+  const { createUntilExpression } = require('../expressions/until');
   const { createSpreadExpression } = require('../expressions/spread');
 
   const composeBinaryExpression = (context, head, tail) => {
@@ -302,6 +304,22 @@ IfBlock "if block"
   }
   / Block
 
+WhileExpression "while expression"
+  = WhileToken __ '(' __ e:Expression __ ')' __ loopBlock:LoopBlock {
+    return createWhileExpression(createLocation(location(), options), e, loopBlock);
+  }
+
+UntilExpression "until expression"
+  = UntilToken __ '(' __ e:Expression __ ')' __ loopBlock:LoopBlock {
+    return createUntilExpression(createLocation(location(), options), e, loopBlock);
+  }
+
+LoopBlock "loop block"
+  = e:AssignmentExpression {
+    return createBlockExpression(createLocation(location(), options), [e]);
+  }
+  / Block
+
 SpreadExpression "spread"
   = '...' e:Expression {
     return createSpreadExpression(createLocation(location(), options), e);
@@ -319,6 +337,8 @@ PrimaryExpression
     return e;
   }
   / IfExpression
+  / WhileExpression
+  / UntilExpression
   / SpreadExpression
 
 Literal
@@ -505,6 +525,8 @@ ReservedWord
   / FalseToken
   / IfToken
   / ElseToken
+  / WhileToken
+  / UntilToken
   / AndToken
   / OrToken
   / NotToken
@@ -517,6 +539,8 @@ TrueToken = "true" !IdentifierPart
 FalseToken = "false" !IdentifierPart
 IfToken = "if" !IdentifierPart
 ElseToken = "else" !IdentifierPart
+WhileToken = "while" !IdentifierPart
+UntilToken = "until" !IdentifierPart
 AndToken = $("and" !IdentifierPart)
 OrToken = $("or" !IdentifierPart)
 NotToken = "not" !IdentifierPart { return 'not'; }