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Parser
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license: mit |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
<!DOCTYPE html> | |
<head> | |
<meta charset="utf-8"> | |
</head> | |
<body> | |
<script> | |
function isLetter(str) { | |
return str.match(/[a-z]/i); | |
} | |
function parse(str) { | |
// Parse the next token. | |
// We assume each token is a single character. | |
var i = 0, sym; | |
function nextSym () { | |
sym = str[i++]; | |
if (sym && isLetter(sym)) { | |
sym += str[i++] | |
} | |
} | |
function symType () { | |
if (sym === "/" || sym === "+") { | |
return "operator"; | |
} | |
if (sym === "(" || sym === ")") { | |
return "paren"; | |
} | |
return "name"; | |
} | |
// Our grammar: | |
// expression = ["+"] term {("+") term} . | |
// term = factor {("/") factor} . | |
// factor = | |
// name | |
// | "(" expression ")" . | |
function factor (){ | |
if (symType() === "name") { | |
var name = sym; | |
nextSym(); | |
return name; | |
} | |
if (sym === "(") { | |
nextSym(); | |
var result = expression(); | |
if (sym === ")") { | |
nextSym(); | |
return result; | |
} | |
console.error("Expected end paren ')'.") | |
} | |
} | |
function operator (symbol, orientation, fn){ | |
return function () { | |
var result = fn(); | |
if (sym !== symbol) { | |
return result; | |
} | |
var children = [result]; | |
while (sym === symbol) { | |
nextSym(); | |
children = children.concat(fn()); | |
} | |
return { | |
orientation: orientation, | |
children: children | |
}; | |
} | |
} | |
var term = operator("/", "vertical", factor); | |
var expression = operator("+", "horizontal", term); | |
nextSym(); | |
return expression(); | |
} | |
function test (str, expected){ | |
if (JSON.stringify(parse(str)) !== JSON.stringify(expected)) { | |
console.error("Test failed for " + str); | |
console.error(JSON.stringify(parse(str))); | |
} | |
} | |
console.log("Running tests..."); | |
test("A", "A"); | |
test("A/B", { "orientation": "vertical", "children": ["A", "B"] }); | |
test("A+B", { "orientation": "horizontal", "children": ["A", "B"] }); | |
test("A/B/C", { "orientation": "vertical", "children": ["A", "B", "C"] }); | |
test("A+B+C", { "orientation": "horizontal", "children": ["A", "B", "C"] }); | |
test("A/B+C", { | |
"orientation": "horizontal", | |
"children": [ { "orientation": "vertical", "children": ["A", "B"] }, "C" ] | |
}); | |
test("A+B/C", { | |
"orientation": "horizontal", | |
"children": [ "A", { "orientation": "vertical", "children": ["B", "C"] } ] | |
}); | |
test("(A)", "A"); | |
test("(A/B)", { "orientation": "vertical", "children": ["A", "B"] }); | |
test("(A+B)", { "orientation": "horizontal", "children": ["A", "B"] }); | |
test("(A)/B", { "orientation": "vertical", "children": ["A", "B"] }); | |
test("A+(B)", { "orientation": "horizontal", "children": ["A", "B"] }); | |
test("(A)/B", { "orientation": "vertical", "children": ["A", "B"] }); | |
test("(A)+(B)", { "orientation": "horizontal", "children": ["A", "B"] }); | |
test("((A))", "A"); | |
test("((A)+(B))", { "orientation": "horizontal", "children": ["A", "B"] }); | |
test("(A)/(B)/(C)", { "orientation": "vertical", "children": ["A", "B", "C"] }); | |
test("A/(B/C)", { | |
"orientation":"vertical", | |
"children":["A",{"orientation":"vertical","children":["B","C"]}] | |
}); | |
test("(A/B)/C", { | |
"orientation":"vertical", | |
"children":[{"orientation":"vertical","children":["A","B"]},"C"] | |
}); | |
test("A+(B+C)", { | |
"orientation": "horizontal", | |
"children":["A",{"orientation":"horizontal","children":["B","C"]}] | |
}); | |
test("A/(B+C)", { | |
"orientation": "vertical", | |
"children":["A",{"orientation":"horizontal","children":["B","C"]}] | |
}); | |
test("A/(B+C/D+E)", { | |
"orientation":"vertical", | |
"children":[ | |
"A", | |
{ | |
"orientation":"horizontal", | |
"children":[ | |
"B", | |
{"orientation":"vertical","children":["C","D"]}, | |
"E" | |
] | |
} | |
] | |
}); | |
test("Foo", "Foo"); | |
console.log("Ran all tests!"); | |
//var complexCase = "A/(B+C/D+E)"; | |
</script> | |
</body> |
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