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Read an indeterminate power under a function through its exponent - #2381
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Rafael-SOWNet merged 1 commit intoNov 7, 2026
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x^x at 0+ is 1, and sin(x^x) there was unevaluated. The rule that reads 0^0 and oo^0 through the exponent, e^(g ln f), was asked only of a whole expression at the top level; the descent substituted the parts' limits, met 0^0, evaluated it to NaN, and the function above it had nothing. The power's descent now asks the same rule of the power, one-sided or at an infinity as the top level asks it, and only where the base is positive on the side approached, so the power is real there. x^x on the left of 0 is complex, and the two-sided limits there stay as they were. Where the rule settles nothing, the pair is substituted as before. sqrt(x) / x^pi + x^x at 0+ is answered +oo by it, which its test said was not answered yet; the row moves to an assertion of the value. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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## master #2381 +/- ##
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+ Coverage 86.75% 86.78% +0.02%
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Files 312 312
Lines 69072 69095 +23
Branches 20149 20151 +2
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+ Hits 59925 59961 +36
+ Misses 4931 4918 -13
Partials 4216 4216
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Rafael-SOWNet
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November 7, 2026 12:24
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x^xat 0 from the right is 1, butsin(x^x)there came back unevaluated (2.6.0 answered NaN). The rule that reads 0^0, 1^oo and oo^0 through the exponent was only asked of a whole expression. A power inside a function was substituted instead: 0^0 became NaN, and the function above had nothing to work with.A power in the descent now asks that rule itself, under these conditions:
(-x)^xat 0 two-sided would answer 1 while its mirrorx^xstays NaN. Which branch each side takes is Read a limit's value at a continuous point before simplifying #2365's open question, and this PR does not answer it. Both stay NaN.sin(x^x), 0 from the rightNaNsin(1)cos(x^x), 0 from the rightNaNcos(1)sin((x - 1)^ln(x)), 1 from the rightNaNsin(1)sin(x^(1/x)), +oosin(1)sqrt(x)/x^pi + x^x, 0 from the rightNaN+ooAnInfinityIsNotACoefficientTestrecorded the last row as not yet answered, so that test now asserts +oo.Unchanged:
x^x,(-x)^xandsin(x^x)at 0 two-sided stay NaN, andsin(x^x)from the left stays unevaluated.Measured
DEPTH=3, across 42 seeds against master: 139 more limits are answered, each agreeing with the values, and no answer disagrees.1/abs(x)^xat 0 is 1. Its base is real on both sides, so this is not Read a limit's value at a continuous point before simplifying #2365's question.x^(abs(x)^arctan(2))at 0 from each side, and one quotient at -1. Timed alone, each takes about 5 s on both builds.Found by limitcheck; no issue was filed.
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