Feature language generator and Chomsky normal form

.travis.yml

@@ -12,7 +12,7 @@ before_script:
   - ./cc-test-reporter before-build
 
 script:
-  - npm run cover
+  - npm run travis
 
 after_script:
   - ./cc-test-reporter after-build --exit-code $TRAVIS_TEST_RESULT

README.md

@@ -4,8 +4,8 @@
 Grammar compilation toolkit for JavaScript. Served with asynchronous goodness.
 See [docs](https://aureooms.github.io/js-grammar/index.html).
 
-> :warning: The code needs a ES2015+ polyfill to work (`regeneratorRuntime`),
-> for instance [@babel/polyfill](https://babeljs.io/docs/usage/polyfill).
+> :warning: The code requires `regeneratorRuntime` to be defined, for instance by importing
+> [regenerator-runtime/runtime](https://www.npmjs.com/package/regenerator-runtime).
 
 ```js
 const G = grammar.from( { root , start , eof , productions } ) ;

doc/manual/usage.md

@@ -1,13 +1,13 @@
 # Usage
 
-> :warning: The code needs a ES2015+ polyfill to work (`regeneratorRuntime`),
-> for instance [@babel/polyfill](https://babeljs.io/docs/usage/polyfill).
+> :warning: The code requires `regeneratorRuntime` to be defined, for instance by importing
+> [regenerator-runtime/runtime](https://www.npmjs.com/package/regenerator-runtime).
 
 First, require the polyfill at the entry point of your application
 ```js
-require( '@babel/polyfill' ) ;
+require( 'regenerator-runtime/runtime' );
 // or
-import '@babel/polyfill' ;
+import 'regenerator-runtime/runtime.js' ;
 ```
 
 Then, import the library where needed

package.json

@@ -5,7 +5,7 @@
   "author": "aureooms",
   "ava": {
     "require": [
-      "@babel/polyfill",
+      "regenerator-runtime/runtime",
       "@babel/register"
     ],
     "files": [
@@ -17,11 +17,57 @@
     "presets": [
       "@babel/preset-env"
     ],
-    "plugins": [
-      "@babel/plugin-proposal-async-generator-functions"
-    ],
     "env": {
+      "test": {
+        "presets": [
+          "babel-preset-power-assert"
+        ],
+        "plugins": [
+          [
+            "transform-remove-console",
+            {
+              "exclude": [
+                "log",
+                "error",
+                "warn"
+              ]
+            }
+          ]
+        ],
+        "sourceMaps": "inline"
+      },
       "development": {
+        "presets": [
+          "babel-preset-power-assert"
+        ],
+        "plugins": [
+          [
+            "transform-remove-console",
+            {
+              "exclude": [
+                "log",
+                "error",
+                "warn"
+              ]
+            }
+          ]
+        ],
+        "sourceMaps": "inline"
+      },
+      "production": {
+        "plugins": [
+          "babel-plugin-unassert",
+          [
+            "transform-remove-console",
+            {
+              "exclude": [
+                "log",
+                "error",
+                "warn"
+              ]
+            }
+          ]
+        ],
         "sourceMaps": "inline"
       }
     }
@@ -30,26 +76,32 @@
     "url": "https://github.com/aureooms/js-grammar/issues"
   },
   "dependencies": {
-    "@aureooms/js-itertools": "^4.0.1"
+    "@aureooms/js-itertools": "^4.1.0",
+    "@aureooms/js-pairs": "^0.0.0",
+    "@aureooms/js-red-black-tree": "^2.0.7"
   },
   "devDependencies": {
-    "@aureooms/js-compare": "1.4.5",
+    "@aureooms/js-compare": "1.4.8",
     "@aureooms/js-tape": "7.0.0",
-    "@babel/cli": "7.10.5",
-    "@babel/core": "7.11.0",
+    "@babel/cli": "7.11.6",
+    "@babel/core": "7.11.6",
     "@babel/plugin-proposal-async-generator-functions": "7.10.5",
-    "@babel/polyfill": "7.10.4",
-    "@babel/preset-env": "7.11.0",
-    "@babel/register": "7.10.5",
-    "ava": "3.11.1",
+    "@babel/preset-env": "7.11.5",
+    "@babel/register": "7.11.5",
+    "ava": "3.12.1",
+    "babel-plugin-transform-remove-console": "6.9.4",
+    "babel-plugin-unassert": "3.0.1",
+    "babel-preset-power-assert": "3.0.0",
     "coveralls": "3.1.0",
     "esdoc": "1.1.0",
     "esdoc-ecmascript-proposal-plugin": "1.0.0",
     "esdoc-inject-script-plugin": "1.0.0",
     "esdoc-inject-style-plugin": "1.0.0",
     "esdoc-standard-plugin": "1.0.0",
-    "np": "6.3.2",
-    "nyc": "15.1.0"
+    "np": "6.5.0",
+    "nyc": "15.1.0",
+    "power-assert": "1.6.1",
+    "regenerator-runtime": "0.13.7"
   },
   "files": [
     "lib"
@@ -67,12 +119,14 @@
     "url": "https://github.com/aureooms/js-grammar"
   },
   "scripts": {
-    "build": "rm -rf lib && babel src -d lib",
+    "build": "babel --delete-dir-on-start --env-name production src -d lib",
     "cover": "nyc --reporter=lcov npm test",
+    "dev": "npm run cover -- -- -st --fail-fast",
     "esdoc": "esdoc",
     "prepare": "npm run build",
     "release": "np",
-    "test": "ava"
+    "test": "ava",
+    "travis": "npm run cover"
   },
   "sideEffects": false
 }

src/ast/flatten.js

@@ -1,3 +1,4 @@
+import assert from 'assert' ;
 import { anyIterator } from '../util' ;
 
 function getCount ( object ) {
@@ -7,7 +8,7 @@ function getCount ( object ) {
 
 export default async function* flatten ( root ) {
 
-	// assert root.type === 'node'
+	assert(root.type === 'node');
 
 	const stack = [
 		{ // no need to use the exhaustive iterator since flatten exhausts the whole subtree

src/ast/index.js

@@ -7,6 +7,7 @@ import materialize from './materialize' ;
 import rmap from './rmap' ;
 import transform from './transform' ;
 
+/* eslint import/no-anonymous-default-export: [2, {"allowObject": true}] */
 export default {
 	Children ,
 	_children_exhaust ,

src/ast/materialize.js

@@ -1,8 +1,9 @@
+import assert from 'assert';
 import { anyIterator } from '../util' ;
 
 export default async function materialize ( root ) {
 
-	// assert root.type === 'node'
+	assert(root.type === 'node');
 
 	const parents = [
 		{

src/ast/transform.js

@@ -1,5 +1,7 @@
+import assert from 'assert' ;
+
 export default async function transform ( tree , match , ctx ) {
-	// assert tree.type === 'node'
+	assert(tree.type === 'node');
 	const { nonterminal , production } = tree ;
 	return await match[nonterminal][production]( tree , match , ctx ) ;
 }

src/cfg/index.js

@@ -0,0 +1,13 @@
+import nullable from './nullable' ;
+import unitrules from './unitrules' ;
+
+/* eslint import/no-anonymous-default-export: [2, {"allowObject": true}] */
+export default {
+	nullable ,
+	unitrules ,
+} ;
+
+export {
+	nullable ,
+	unitrules ,
+} ;

src/cfg/nullable.js

@@ -0,0 +1,53 @@
+import assert from 'assert' ;
+import { list , any , map , all } from '@aureooms/js-itertools' ;
+import { simplify_zol_system_dnf_no_negation } from '../math/logic' ;
+
+/**
+ * Compute the set of nullable terminals from a list of productions.
+ *
+ * NB: this corresponds to computing the set of variables that are true given a
+ * system of equations in disjunctive normal form. Given the grammar
+ *
+ *     A -> B | BB | C
+ *     B -> CC | b
+ *     C -> C | ε
+ *
+ * we get the following system of equations
+ *
+ *     A = B or (B and B) or C
+ *     B = (C and C) or FALSE
+ *     C = C or TRUE
+ *
+ * where terminals have been replaced by FALSE and the empty word has been
+ * replaced by TRUE.
+ *
+ * The solution for this example is
+ *
+ *     A = B = C = TRUE
+ *
+ * If some symbol is not defined (has no productions) then it is FALSE (empty
+ * disjunction).
+ *
+ * TODO Use solver for this kind of system instead of ad-hoc code.
+ *
+ * @param {Iterable} productions - A sequence of (nonterminal, rule) pairs.
+ * @return {Set} The set of nullable terminals.
+ */
+export default function nullable ( productions ) {
+
+	const system = nullable_zol_system_dnf_no_negation(productions);
+	return simplify_zol_system_dnf_no_negation(system);
+
+}
+
+function* nullable_zol_system_dnf_no_negation ( productions ) {
+
+	for ( const [ nonterminal , rule ] of productions ) {
+		assert(typeof nonterminal === 'string');
+		assert(rule instanceof Array);
+		if (any(map(x => x.type === 'leaf', rule))) continue ;
+		assert(all(map(x => x.type === 'node', rule))) ;
+		yield [ nonterminal , list(map(x => x.nonterminal, rule)) ] ;
+	}
+
+}

src/cfg/unitrules.js

@@ -0,0 +1,11 @@
+export default function* unitrules ( productions ) {
+
+	for ( const [A, rule] of productions ) {
+		if ( rule.length === 1 && rule[0].type === 'node' ) {
+			// A -> B
+			const B = rule[0].nonterminal ;
+			yield [A, B];
+		}
+	}
+
+}