// 4.2.js
// 2024-09-03
// $Id: 4.2.js 1.1 2024/10/26 13:57:12 s Exp $
// s, current spot rate curve
// s2, next year's spot rate curve

'use strict'
// function
const f_1 = function (j){ // forward rate, i = 1
    return ((1 + s[j]) ** j / (1 + s[1])) ** (1 / (j - 1)) - 1;
}

// input
const s_percent = [0, 5.0, 5.3, 5.6, 5.8, 6.0, 6.1];

// calculating
const s   = s_percent.map(x => x / 100);
const sd1 = (((1 + s[2]) ** 2 / (1 + s[1])) ** (1 / (2-1)) - 1) * 100;
const sd2 = (((1 + s[3]) ** 3 / (1 + s[1])) ** (1 / (3-1)) - 1) * 100;
const sd3 = (((1 + s[4]) ** 4 / (1 + s[1])) ** (1 / (4-1)) - 1) * 100;
const sd4 = (((1 + s[5]) ** 5 / (1 + s[1])) ** (1 / (5-1)) - 1) * 100;
const sd5 = (((1 + s[6]) ** 6 / (1 + s[1])) ** (1 / (6-1)) - 1) * 100;
const sd  = [sd1, sd2, sd3, sd4, sd5];
let   s2  = [0];
for(let j = 2; j < s.length; j++ ){
    s2[j - 1] = f_1(j);
}

// output
console.log('4.2.js');
console.log("current spot rate curve");
console.log("s=", ...s_percent.map(x => x.toFixed(1)));
console.log("next year's spot rate curve");
console.log("calculating without function");
console.log(...sd.map(x => x.toFixed(1)));
console.log("calculating with function");
console.log(...s2.map(x => (x * 100).toFixed(1)));
// end

// reference 
// David Flanagan著 『JavaScript 第7版』(オライリー・ジャパン) 2022-09-13.
// ... : p.215.
// ** : p.80.
// => : p.202.
// console.log() : p.630.
// const : p.57.
// length : p.176.
// let : p.57.
// map() : p.182.
// toFixed() : p.51.
// use strict : p.134.
// end reference