Merge pull request #22 from streamich/calculator

Calculator

Author: streamich

src/grammars/__tests__/calculator.spec.ts

@@ -0,0 +1,33 @@
+import {CodegenGrammar} from '../../codegen/CodegenGrammar';
+import {CodegenContext, ParseContext} from '../../context';
+import {GrammarPrinter, printCst, printTraceNode} from '../../print';
+import {RootTraceNode} from '../../types';
+import {grammar} from '../calculator';
+
+const codegenCtx = new CodegenContext(true, true, true);
+const codegen = new CodegenGrammar(grammar, codegenCtx);
+
+const toCst = (src: string) => {
+  const parser = codegen.compile();
+  const trace: RootTraceNode = {pos: 0, children: []};
+  const ctx = new ParseContext(src, true, [trace]);
+  const cst = parser(ctx, 0)!;
+  // console.log(printTraceNode(trace.children[0], '', src));
+  // console.log(printCst(cst, '', src));
+  return {cst, trace};
+};
+
+const toAst = (src: string) => {
+  const cst = toCst(src);
+  const ast = cst.cst.ptr.toAst(cst.cst, src);
+  return {...cst, ast};
+};
+
+test('can evaluate a simple expression', () => {
+  const text = '2 * 2 + 4 * 3';
+  const res = toAst(text);
+  // console.log(GrammarPrinter.print(grammar));
+  // console.log(printTraceNode(res.trace, '', text));
+  // console.log(printCst(res.cst, '', text));
+  expect(res.ast).toBe(16);
+});

src/grammars/calculator.ts

@@ -0,0 +1,83 @@
+import type {Grammar} from '../types';
+
+/**
+ * A simple math expression grammar.
+ */
+export const grammar: Grammar = {
+  start: 'SingleExpression',
+
+  cst: {
+    Whitespace: {t: /\s*/, ast: null},
+
+    SingleExpression: {
+      p: [{r: 'Whitespace'}, {r: 'Expression'}, {r: 'Whitespace'}],
+      ast: ['$', '/children/0'],
+    },
+
+    Expression: {
+      u: [{r: 'AdditiveExpression'}, {r: 'Literal'}],
+      ast: ['$', '/children/0'],
+    },
+
+    AdditiveExpression: {
+      p: [{r: 'MultiplicativeExpression'}, {r: 'AdditiveExpressionCont'}],
+      ast: [
+        '?',
+        ['==', ['len', ['$', '/children']], 1],
+        ['$', '/children/0'],
+        [
+          '?',
+          ['==', ['$', '/children/1/children/0'], '+'],
+          ['+', ['$', '/children/0'], ['$', '/children/1/children/1', 1]],
+          ['-', ['$', '/children/0'], ['$', '/children/1/children/1', 1]],
+        ],
+      ],
+    },
+    AdditiveExpressionCont: {
+      u: [
+        [
+          {r: 'Whitespace'},
+          {t: ['+', '-'], ast: ['$', '/raw']},
+          {r: 'Whitespace'},
+          {r: 'AdditiveExpression'},
+          {r: 'AdditiveExpressionCont'},
+        ],
+        '',
+      ],
+      ast: ['$', '/children/0', 0],
+    },
+
+    MultiplicativeExpression: {
+      p: [{r: 'Literal'}, {r: 'MultiplicativeExpressionCont'}],
+      ast: [
+        '?',
+        ['==', ['len', ['$', '/children']], 1],
+        ['$', '/children/0'],
+        [
+          '?',
+          ['==', ['$', '/children/1/children/0'], '*'],
+          ['*', ['$', '/children/0'], ['$', '/children/1/children/1', 1]],
+          ['/', ['$', '/children/0'], ['$', '/children/1/children/1', 1]],
+        ],
+      ],
+    },
+    MultiplicativeExpressionCont: {
+      u: [
+        [
+          {r: 'Whitespace'},
+          {t: ['*', '/'], ast: ['$', '/raw']},
+          {r: 'Whitespace'},
+          {r: 'MultiplicativeExpression'},
+          {r: 'MultiplicativeExpressionCont'},
+        ],
+        '',
+      ],
+      ast: ['$', '/children/0', 0],
+    },
+
+    Literal: {
+      t: /\d+/,
+      ast: ['num', ['$', '/raw']],
+    },
+  },
+};