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fix(log): ensure series expansion can handle small x values #23

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Merged
nberlette merged 2 commits into from
Jan 24, 2026
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fix(log): ensure series expansion can handle small x values #23

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fix(log): ensure series expansion can handle small x values
nberlette Jan 24, 2026
4d0ee56
chore: update lockfile
nberlette Jan 24, 2026
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4 changes: 4 additions & 0 deletions deno.lock
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1 change: 1 addition & 0 deletions src/log.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ export function log(x: number): number {
const seriesEpsilon = EPSILON * 16;
let n = 0;
while (x > 2) x /= 2, n++;
while (x < 0.5) x *= 2, n--;
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Copilot AI Jan 24, 2026

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PR metadata says it fixes issue #22 about fround hanging on small values, but this change only affects log() (and fround() does not call log() in this repo). Please either update the linked issue/PR description to reflect the actual bug being fixed, or include the corresponding fround fix if that's the intended target.

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Copilot AI Jan 24, 2026

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This change addresses convergence for x < 0.5, but the existing tests for log() only cover down to 0.5. Add test cases for very small positive values (e.g., Number.MIN_VALUE, 1e-300, subnormals) to prevent regressions (including non-termination/timeouts) and to validate accuracy against Math.log.

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const z = (x - 1) / (x + 1), z2 = z * z;
let sum = 0, term = z, i = 1;
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