Revision eae1904af2d80d198ecfb1b68a8b24251fd8fca0 authored by Andreas Stuhlmüller on 02 July 2017, 19:45:35 UTC, committed by GitHub on 02 July 2017, 19:45:35 UTC
Expand docs on conditioning
syntax.js
'use strict';
var types = require('ast-types').namedTypes;
var build = require('ast-types').builders;
var keys = require('estraverse').VisitorKeys;
var Syntax = require('estraverse').Syntax;
function makeGenvar() {
var gensym = require('./util').makeGensym();
return function(name) {
return build.identifier('_'.concat(gensym(name)));
};
}
function fail(message, node) {
return function() {
console.log(node);
console.log(message);
throw new Error(message);
};
}
// a clause matches a node type and calls a destructor with constituents
// a clause is a function from a node and failure thunk to a result
function clause(type, destructor) {
return function(node, fail) {
if (types.hasOwnProperty(type)) {
if (types[type].check(node)) {
return destructor.apply(this, keys[type].map(function(key) {
return node[key];
}));
}
else {
return fail();
}
}
else {
throw new Error('no type ' + type);
}
};
}
function match(node, clauses, fail) {
for (var i = 0; i < clauses.length; i++) {
var failed = false;
var value = clauses[i](node, function() {failed = true});
if (!failed) {
return value;
}
}
return fail();
}
function failSafe(who, fail) {
if (typeof fail === 'function') {
return fail();
}
else {
throw new Error(who + ': fail is not a function');
}
}
function inProgram(f, fail) {
return function(node) {
if (types.Program.check(node) &&
node.body.length === 1 &&
types.ExpressionStatement.check(node.body[0])) {
return build.program([
build.expressionStatement(f(node.body[0].expression))
]);
}
else {
return failSafe('inProgram', fail);
}
};
}
function inBody(f, fail) {
return inProgram(function(node) {
if (types.FunctionExpression.check(node)) {
return build.functionExpression(
node.id,
node.params,
build.blockStatement(f(build.program(node.body.body)).body));
}
else {
return failSafe('inBody', fail);
}
}, fail);
}
function returnify(nodes) {
if (nodes.length === 0) {
return nodes;
}
else {
var returnNode = match(nodes[nodes.length - 1], [
clause(Syntax.BlockStatement, function(body) {
return build.blockStatement(returnify(body));
}),
clause(Syntax.EmptyStatement, function() {
return build.emptyStatement();
}),
clause(Syntax.ExpressionStatement, function(expression) {
return build.returnStatement(expression);
}),
clause(Syntax.IfStatement, function(test, consequent, alternate) {
return build.ifStatement(
test,
build.blockStatement(returnify(consequent.body)),
alternate === null ? null : build.blockStatement(returnify([alternate])));
}),
clause(Syntax.ReturnStatement, function(argument) {
return build.returnStatement(argument);
})
], function() { return; });
if (returnNode) {
nodes[nodes.length - 1] = returnNode;
} else {
nodes = nodes.concat(build.returnStatement(build.identifier('undefined')));
}
return nodes;
}
}
function isPrimitive(node) {
switch (node.type) {
case Syntax.FunctionExpression:
case Syntax.Identifier:
case Syntax.CallExpression:
case Syntax.ConditionalExpression:
return false;
case Syntax.MemberExpression:
return (types.Identifier.check(node.object) ||
(!node.computed) && types.Identifier.check(node.property));
default:
console.log(node);
throw new Error("isPrimitive doesn't handle node");
}
}
function thunkify(node, fail) {
if (types.Program.check(node)) {
return build.program([
build.expressionStatement(
build.functionExpression(
null,
[],
build.blockStatement(returnify(node.body))
)
)
]);
}
else {
return failSafe('thunkify', fail);
}
}
module.exports = {
makeGenvar: makeGenvar,
fail: fail,
clause: clause,
match: match,
thunkify: thunkify,
inProgram: inProgram,
inBody: inBody,
isPrimitive: isPrimitive
};
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