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trampoline.js
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trampoline.js
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'use strict';
var replace = require('estraverse').replace;
var Syntax = require('estraverse').Syntax;
var build = require('ast-types').builders;
var types = require('ast-types').namedTypes;
var parse = require('esprima').parse;
var fail = require('../syntax').fail;
var inProgram = require('../syntax').inProgram;
var isPrimitive = require('../syntax').isPrimitive;
function thunkify(node) {
return build.functionExpression(
null, [],
build.blockStatement([
build.returnStatement(node)
]), false, false);
}
function skip(node) {
if (types.ReturnStatement.check(node)) {
this.skip();
}
}
function trampoline(node) {
switch (node.type) {
// re-direct all non-primitive calls through trampoline
// this is only okay in cps where no implicit stack is used!
case Syntax.ExpressionStatement:
switch (node.expression.type) {
case Syntax.CallExpression:
if (isPrimitive(node.expression.callee)) {
return node;
}
else {
return build.returnStatement(thunkify(node.expression));
}
default:
return build.returnStatement(thunkify(node.expression));
}
default:
return node;
}
}
var driver = parse(
['(function(p) {',
' return function(s, k, a) {',
' var trampoline = p(s, k, a);',
' while (trampoline) {',
' trampoline = trampoline();',
' }',
' }',
'})'].join('\n')
).body[0].expression;
function trampolineMain(node) {
return inProgram(function(node) {
return build.callExpression(driver, [replace(node, {
enter: skip,
leave: trampoline
})]);
})(node, fail('trampoline', node));
}
module.exports = {
trampoline: trampolineMain
};