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node_modules/recast/example/to-while

@@ -0,0 +1,84 @@
+#!/usr/bin/env node
+
+// This script converts for and do-while loops into equivalent while loops.
+// Note that for-in statements are left unmodified, as they do not have a
+// simple analogy to while loops. Also note that labeled continue statements
+// are not correctly handled at this point, and will trigger an assertion
+// failure if encountered.
+
+var assert = require("assert");
+var recast = require("recast");
+var types = recast.types;
+var n = types.namedTypes;
+var b = types.builders;
+
+recast.run(function(ast, callback) {
+    recast.visit(ast, {
+        visitForStatement: function(path) {
+            var fst = path.node;
+
+            path.replace(
+                fst.init,
+                b.whileStatement(
+                    fst.test,
+                    insertBeforeLoopback(fst, fst.update)
+                )
+            );
+
+            this.traverse(path);
+        },
+
+        visitDoWhileStatement: function(path) {
+            var dwst = path.node;
+            return b.whileStatement(
+                b.literal(true),
+                insertBeforeLoopback(
+                    dwst,
+                    b.ifStatement(
+                        dwst.test,
+                        b.breakStatement()
+                    )
+                )
+            );
+        }
+    });
+
+    callback(ast);
+});
+
+function insertBeforeLoopback(loop, toInsert) {
+    var body = loop.body;
+
+    if (!n.Statement.check(toInsert)) {
+        toInsert = b.expressionStatement(toInsert);
+    }
+
+    if (n.BlockStatement.check(body)) {
+        body.body.push(toInsert);
+    } else {
+        body = b.blockStatement([body, toInsert]);
+        loop.body = body;
+    }
+
+    recast.visit(body, {
+        visitContinueStatement: function(path) {
+            var cst = path.node;
+
+            assert.equal(
+                cst.label, null,
+                "Labeled continue statements are not yet supported."
+            );
+
+            path.replace(toInsert, path.node);
+            return false;
+        },
+
+        // Do not descend into nested loops.
+        visitWhileStatement: function() {},
+        visitForStatement: function() {},
+        visitForInStatement: function() {},
+        visitDoWhileStatement: function() {}
+    });
+
+    return body;
+}