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18 lines
330 B
18 lines
330 B
10 years ago
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'use strict';
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var exp = Math.exp;
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module.exports = function (x) {
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var a, b;
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if (isNaN(x)) return NaN;
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x = Number(x);
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if (x === 0) return x;
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if (x === Infinity) return 1;
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if (x === -Infinity) return -1;
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a = exp(x);
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if (a === Infinity) return 1;
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b = exp(-x);
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if (b === Infinity) return -1;
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return (a - b) / (a + b);
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};
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