Created
August 24, 2021 17:10
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function parse(fullString) { | |
let strArray = fullString.split(" "); | |
let pos = 0; | |
function checkPos() { | |
return strArray[pos]; | |
} | |
function isNumber(e) { | |
return e !== undefined && e.match(/^-?([1-9][0-9]*|([0]))$/) !== null; | |
} | |
function jumpNext() { | |
pos++; | |
} | |
function parseNumber() { | |
let k = checkPos(); | |
if (isNumber(k)) { | |
jumpNext(); | |
return { type: "number", value: k }; | |
} else { | |
throw SyntaxError("Invalid Format"); | |
} | |
} | |
function parseMulDiv() { | |
let expr = parseNumber(); | |
let k = checkPos(); | |
while (k === "*" || k === "/") { | |
jumpNext(); | |
let rhs = parseNumber(); | |
expr = { type: k, left: expr, right: rhs }; | |
k = checkPos(); | |
} | |
return expr; | |
} | |
function parseAddSub() { | |
let expr = parseMulDiv(); | |
let k = checkPos(); | |
while (k === "-" || k === "+") { | |
jumpNext(); | |
let rhs = parseMulDiv(); | |
expr = { type: k, left: expr, right: rhs }; | |
k = checkPos(); | |
} | |
return expr; | |
} | |
let output = parseAddSub(); | |
return output; | |
} |
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