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15 lines
289 B
JavaScript
15 lines
289 B
JavaScript
'use strict';
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var log = Math.log;
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module.exports = function (x) {
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if (isNaN(x)) return NaN;
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x = Number(x);
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if (x < -1) return NaN;
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if (x > 1) return NaN;
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if (x === -1) return -Infinity;
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if (x === 1) return Infinity;
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if (x === 0) return x;
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return 0.5 * log((1 + x) / (1 - x));
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};
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