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zhuangzhuang/rational.ts

Created March 28, 2017 17:12
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  1. zhuangzhuang created this gist Mar 28, 2017.
    88 changes: 88 additions & 0 deletions rational.ts
    View file
    Original file line number Diff line number Diff line change
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    class Rational {
    readonly number: number
    readonly denom: number
    // -------------- public ----------
    constructor(n: number, d: number){
    this.number = n
    this.denom = d
    }

    add(that): Rational{
    return this._translate(that, (this_n, this_d, that_n, that_d)=>{
    const n = this_n * that_d + that_n * this_d
    const d = this_d * that_d
    return {n, d}
    });
    }
    sub(that): Rational {
    return this._translate(that, (this_n, this_d, that_n, that_d)=>{
    const n = this_n * that_d - that_n * this_d
    const d = this_d * that_d
    return {n, d}
    });
    }
    mul(that): Rational {
    return this._translate(that, (this_n, this_d, that_n, that_d)=>{
    const n = this_n * that_n
    const d = this_d * that_d
    return {n, d}
    });
    }
    div(that): Rational {
    return this._translate(that, (this_n, this_d, that_n, that_d)=>{
    const n = this_n * that_d
    const d = this_d * that_n
    return {n, d}
    });
    }

    toFloat(){
    return this.number / this.denom
    }

    // --------------- static ------------
    static of(n): Rational {
    if(n instanceof Rational) {
    return n;
    }
    if(typeof n === 'string'){
    n = parseFloat(n)
    }
    if(typeof n !== "number"){
    throw new Error("invalidate number")
    }
    const num = n.toPrecision()
    const parts = num.split('.')
    var denom = 1
    if(parts.length > 1){
    denom = Math.pow(10, parts[1].length)
    }
    var number = n * denom
    return new Rational(number, denom)
    }

    // private //
    private _translate(_that ,fn: (n:number, d:number, that_n:number, that_d:number)=>{n:number, d:number}) {
    var that = _that
    if(!(that instanceof Rational)){
    that = Rational.of(that)
    }
    const this_n = this.number,
    this_d = this.denom,
    that_n = that.number,
    that_d = that.denom;
    var r = fn(this_n, this_d, that_n, that_d)
    return new Rational(r.n, r.d)
    }
    }

    function safePlus(a, b){
    return Rational.of(a).add(b).toFloat()
    }

    // console.log(safePlus(1, 2))
    // console.log(safePlus(1.1, 2.1))
    // console.log(safePlus(100000.000001, 100000.000001))

    console.log(1213.11 * 10000)
    console.log(safePlus(1213.11, 10000))