関数型プログラミング練習.js

kansuugataProgramming.js

(function() {
    const show = (x) => {
        console.log(x);
    };

    //総和
    var arr = [1, 3, 5, 7, 9];
    show(arr.reduce((x, y) => x + y));

    //最大値
    var arr1 = [1, 10, 4, 30, 2, 9];
    show(arr1.reduce((x, y) => x > y ? x : y));

    //最小値
    var arr2 = [3, 5, 18, -2, 9, 1, -1];
    show(arr2.reduce((x, y) => x > y ? y : x));

    //加算
    const add = (x) => (y) => x + y;
    /*
	次は'const add = (x) => (y) => x + y;'と等価

		    const add = (x) => (y) => {return x + y};

		    const add = function(x){
				return function(y){
					return x + y;
				};
		    };
    */
    let add2 = add(2);
    show(add2(3));
    show(add(5)(6));

    //乗算
    const mul = (x) => (y) => x * y;
    show(mul(5)(6));

    //論理演算
    const T = true;
    const F = false;
    const and = (x) => (y) => x && y;
    const or = (x) => (y) => x || y;

    show(and(T)(F));
    show(or(F)(T));
    show(and(or(F)(F))(and(F)(T)));

    const ln = (x) => Math.log(x);
    const E = Math.E;
    show(ln(E));
    show(-ln(E ** (-3)));


    //偶数の中の最大値
    var arr3 = [10, 3, 4, 5, 21, 8, 9, 2];
    const even = (x) => x % 2 === 0;
    const max = (xs) => Math.max(...xs);
    show(max(arr3.filter(even)));

    //奇数の中の最小値
    const odd = (x) => x % 2 === 1;
    const min = (xs) => Math.min(...xs);
    show(min(arr3.filter(odd)));

    //pipe
    const pipe = (fns) => (x) => fns.reduce((v, f) => f(v), x);

    let op = pipe([add(3),mul(2),add(5),mul(1),add(1),mul(7)]);
    show(op(0));
    show(op(1));
    show(op(3));
    show(pipe([add(1),mul(2),add(3),mul(4)])(1));



    return;
})();