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40 results

number.ts

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  • number.ts 1.51 KiB
    /**
     * Copyright (c) 2018 mol* contributors, licensed under MIT, See LICENSE file for more info.
     */
    
    /**
     * Determine the number of digits in a floating point number
     * Find a number M such that round(M * v) - M * v <= delta.
     * If no such M exists, return -1.
     */
    export function getMantissaMultiplier(v: number, maxDigits: number, delta: number) {
        let m = 1, i;
        for (i = 0; i < maxDigits; i++) {
            let mv = m * v;
            if (Math.abs(Math.round(mv) - mv) <= delta) return i;
            m *= 10;
        }
        return -1;
    }
    
    export function integerDigitCount(v: number, delta: number) {
        const f = Math.abs(v);
        if (f < delta) return 0;
        return Math.floor(Math.log10(Math.abs(v))) + 1;
    }
    
    /**
     * Determine the maximum number of digits in a floating point array.
     * Find a number M such that round(M * v) - M * v <= delta.
     * If no such M exists, return -1.
     */
    export function getArrayDigitCount(xs: ArrayLike<number>, maxDigits: number, delta: number) {
        let mantissaDigits = 1;
        let integerDigits = 0;
        for (let i = 0, _i = xs.length; i < _i; i++) {
            if (mantissaDigits >= 0) {
                const t = getMantissaMultiplier(xs[i], maxDigits, delta);
                if (t < 0) mantissaDigits = -1;
                else if (t > mantissaDigits) mantissaDigits = t;
            }
            const abs = Math.abs(xs[i]);
            if (abs > delta) {
                const d = Math.floor(Math.log10(Math.abs(abs))) + 1;
                if (d > integerDigits) integerDigits = d;
            }
        }
        return { mantissaDigits, integerDigits };
    }