42 lines
1.4 KiB
JavaScript
42 lines
1.4 KiB
JavaScript
/* frac.js (C) 2012-present SheetJS -- http://sheetjs.com */
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var frac = function frac(x/*:number*/, D/*:number*/, mixed/*:?boolean*/)/*:Array<number>*/ {
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var n1 = Math.floor(x), d1 = 1;
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var n2 = n1+1, d2 = 1;
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if(x !== n1) while(d1 + d2 <= D) {
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var m = (n1 + n2) / (d1 + d2);
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if(x === m) {
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if(d1 + d2 <= D) { d2 = (d1+=d2); n2 = (n1+=n2); }
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break;
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}
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else if(x < m) { n2 = n1+n2; d2 = d1+d2; }
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else { n1 = n1+n2; d1 = d1+d2; }
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}
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if(n2 / d2 - x <= x - n1 / d1 ) { d1 = d2; n1 = n2; }
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if(!mixed) return [0, n1, d1];
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var q = Math.floor(n1/d1);
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return [q, n1 - q*d1, d1];
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};
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frac.cont = function cont(x/*:number*/, D/*:number*/, mixed/*:?boolean*/)/*:Array<number>*/ {
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var sgn = x < 0 ? -1 : 1;
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var B = x * sgn;
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var P_2 = 0, P_1 = 1, P = 0;
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var Q_2 = 1, Q_1 = 0, Q = 0;
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var A = Math.floor(B);
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while(Q_1 < D) {
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A = Math.floor(B);
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P = A * P_1 + P_2;
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Q = A * Q_1 + Q_2;
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if((B - A) < 0.00000005) break;
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B = 1 / (B - A);
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P_2 = P_1; P_1 = P;
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Q_2 = Q_1; Q_1 = Q;
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}
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if(Q > D) { if(Q_1 > D) { Q = Q_2; P = P_2; } else { Q = Q_1; P = P_1; } }
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if(!mixed) return [0, sgn * P, Q];
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var q = Math.floor(sgn * P/Q);
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return [q, sgn*P - q*Q, Q];
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};
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/*:: declare var DO_NOT_EXPORT_FRAC: any; */
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// eslint-disable-next-line no-undef
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if(typeof module !== 'undefined' && typeof DO_NOT_EXPORT_FRAC === 'undefined') module.exports = frac;
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