逆ポーランド電卓

逆ポーランド電卓

を作る

実装のポイント

スタックから取り出すときの二項の扱い方

a + b = b + a

a * b = b * a

一時変数においてから計算

code:ts

console.log("execute result:", (() => {

var inputs = "1 2 3 - * 4 5 + +".split(" ");

// var inputs = "2 3 +".split(" ");

var stack = [];

var answer = 0;

type Operator = (a: number, b: number) => number;

var add: Operator = (a, b) => a + b;

var substact: Operator = (a, b) => a - b;

var multiply: Operator = (a, b) => a * b;

var divide: Operator = (a, b) => a / b;

const isOperator = (char: String) =>

"+ - / *"

.split(" ")

.reduce(

(includes, currentOperator) => {

if (includes)

return includes;

return char.includes(currentOperator);

},

false

);

var getFunc = (char: string) => {

if (char === "+")

return add;

else if (char === "-")

return substact;

else if (char === "*")

return multiply;

else if (char === "/")

return divide;

else

return undefined;

}

function factory(a: number) {

if (typeof a === 'undefined')

return undefined;

var f = (b: number) => {

var g = (callback: Function) => {

return callback(a, b);

}

return g;

}

return f;

}

// parse

for (var i = 0; i < inputs.length; ++i) {

var isOp = isOperator(char);

if (isOp) {

var fnc = getFunc(char);

if (typeof fnc === 'undefined')

return 1;

stack.pop();

var f = factory(last);

if (typeof f === 'undefined')

return 2;

stack.pop();

var g = f(last);

var h = g(fnc);

answer = h;

stack.push(answer);

} else {

stack.push(parseInt(char));

}

}

console.log(answer);

return 0;

})());