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Implement major math functions #336

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Implement major math functions #336

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tompng
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@tompng tompng commented Jun 1, 2025

Implement these methods

BigMath.cbrt(x, prec)
BigMath.hypot(x, y, prec)
BigMath.tan(x, prec)
BigMath.asin(x, prec)
BigMath.acos(x, prec)
BigMath.atan2(y, x, prec)
BigMath.sinh(x, prec)
BigMath.cosh(x, prec)
BigMath.tanh(x, prec)
BigMath.asinh(x, prec)
BigMath.acosh(x, prec)
BigMath.atanh(x, prec)
BigMath.log2(x, prec)
BigMath.log10(x, prec)

Remaining methods

Math.singleton_methods - BigMath.singleton_methods
# => [:erf, :erfc, :gamma, :lgamma, :frexp, :ldexp]

@tompng tompng force-pushed the implement_major_math_functions branch from 1a93b02 to 5ebf5dc Compare June 8, 2025 06:30
@mrkn mrkn added this to the v3.4 milestone Jun 17, 2025
@tompng tompng force-pushed the implement_major_math_functions branch 2 times, most recently from f29ba89 to 316d713 Compare June 20, 2025 18:56
mrzasa
mrzasa reviewed Jun 20, 2025
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lib/bigdecimal/math.rb
return BigDecimal::NAN if x.nan?
return BigDecimal::INFINITY if x.infinite? == 1

prec2 = prec + BigDecimal.double_fig * 3 / 2
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Just curious: why do we decide what prec2 is needed? It differs between the functions and I'm wondering how it's calculated.

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Normally, BigMath functions calculate with prec+BigDecimal.double_fig precision.

I think BigMath.log2(1024, prec) is expected to return exactly 10. To calculate exact value for 2**n numbers, we need to round the result to precision = prec+BigDecimal.double_fig.
log(x)/log(2) should be calculated with prec + BigDecimal.double_fig + extra precision.
I decided to use extra=BigDeciaml.double_fig/2 here.

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Thanks!

@tompng tompng force-pushed the implement_major_math_functions branch from 316d713 to a2f13fa Compare June 21, 2025 08:05
@tompng tompng mentioned this pull request Jun 21, 2025
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@tompng tompng force-pushed the implement_major_math_functions branch from a2f13fa to 4385bbd Compare June 30, 2025 11:10
tompng added 3 commits July 19, 2025 23:21
@tompng
Implement BigMath.tan
84048e3 
Calculate `tan(x, prec)` by `relative_precision_sin/relative_precision_cos`.
@tompng
Implement BigMath.atan2(y, x, prec)
352b41b
@tompng
Implement BigMath.hypot(x, y, prec)
f266a47
@tompng tompng force-pushed the implement_major_math_functions branch from 4385bbd to 1c37330 Compare July 19, 2025 14:35
@tompng tompng force-pushed the implement_major_math_functions branch from 1c37330 to f9b5a97 Compare July 19, 2025 15:01
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