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Short circuit evaluation #28

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Merged
merged 5 commits into from
Mar 7, 2020
Merged

Short circuit evaluation #28

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16f9c46
Test for short circuit evaluation
RoboPhred Feb 20, 2020
3eb2207
Implement short circuit evaluation
RoboPhred Feb 20, 2020
c65e1f5
Test short circuit eval for OR
RoboPhred Feb 22, 2020
72cc85d
Implement short circuit eval for OR
RoboPhred Feb 22, 2020
7c6c029
Remove dead branch
goto-bus-stop Mar 7, 2020
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22 changes: 19 additions & 3 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -40,12 +40,30 @@ module.exports = function (ast, vars) {
}
else if (node.type === 'BinaryExpression' ||
node.type === 'LogicalExpression') {
var op = node.operator;

if (op === '&&') {
var l = walk(node.left);
if (l === FAIL) return FAIL;
if (!l) return l;
var r = walk(node.right);
if (r === FAIL) return FAIL;
return r;
}
else if (op === '||') {
var l = walk(node.left);
if (l === FAIL) return FAIL;
if (l) return l;
var r = walk(node.right);
if (r === FAIL) return FAIL;
return r;
}

var l = walk(node.left);
if (l === FAIL) return FAIL;
var r = walk(node.right);
if (r === FAIL) return FAIL;

var op = node.operator;
if (op === '==') return l == r;
if (op === '===') return l === r;
if (op === '!=') return l != r;
Expand All @@ -62,8 +80,6 @@ module.exports = function (ast, vars) {
if (op === '|') return l | r;
if (op === '&') return l & r;
if (op === '^') return l ^ r;
if (op === '&&') return l && r;
if (op === '||') return l || r;

return FAIL;
}
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26 changes: 26 additions & 0 deletions test/eval.js
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Original file line number Diff line number Diff line change
Expand Up @@ -121,3 +121,29 @@ test('constructor at runtime only', function(t) {
var res = evaluate(ast);
t.equal(res, undefined);
});

test('short circuit evaluation AND', function(t) {
t.plan(1);

var variables = {
value: null
};
var src = 'value && value.func()';
var ast = parse(src).body[0].expression;
var res = evaluate(ast, variables);
t.equals(res, null);
})

test('short circuit evaluation OR', function(t) {
t.plan(1);

var fnInvoked = false;
var variables = {
value: true,
fn: function() { fnInvoked = true}
};
var src = 'value || fn()';
var ast = parse(src).body[0].expression;
evaluate(ast, variables);
t.equals(fnInvoked, false);
})