tau.patch
ext/bigdecimal/lib/bigdecimal/math.rb  

7  7 
# sin (x, prec) 
8  8 
# cos (x, prec) 
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# atan(x, prec) Note: x<1, x=0.9999 may not converge. 
10 
# TAU (prec) 

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# PI (prec) 
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# E (prec) == exp(1.0,prec) 
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# 
...  ...  
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y 
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end 
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148 
# See http://tauday.com/ 

149 
def TAU(prec) 

150 
raise ArgumentError, "Zero or negative argument for TAU" if prec <= 0 

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PI(prec)*BigDecimal("2") 

152 
end 

153  
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# Computes the value of pi to the specified number of digits of precision. 
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def PI(prec) 
149  156 
raise ArgumentError, "Zero or negative argument for PI" if prec <= 0 
math.c  

782  782  
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#ifdef M_PI 
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rb_define_const(rb_mMath, "PI", DBL2NUM(M_PI)); 
785 
rb_define_const(rb_mMath, "TAU", DBL2NUM(M_PI*.20)); 

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#else 
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rb_define_const(rb_mMath, "PI", DBL2NUM(atan(1.0)*4.0)); 
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rb_define_const(rb_mMath, "TAU", DBL2NUM(atan(1.0)*8.0)); 

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#endif 
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#ifdef M_E 