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path: root/ext/bigdecimal/lib/pai.rb
blob: 4e2dd7104a1057d887cc71bbd3560d979d9d4c4c (plain)
 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 ``` ``````#!/usr/local/bin/ruby # # pai.rb # require "bigdecimal" # # Calculates 3.1415.... using J. Machin's formula. # def pai(sig) # sig: Number of significant figures exp = -sig pi = BigDecimal::new("0") two = BigDecimal::new("2") m25 = BigDecimal::new("-0.04") m57121 = BigDecimal::new("-57121") u = BigDecimal::new("1") k = BigDecimal::new("1") w = BigDecimal::new("1") t = BigDecimal::new("-80") while (u.exponent >= exp) t = t*m25 u,r = t.div(k,sig) pi = pi + u k = k+two end u = BigDecimal::new("1") k = BigDecimal::new("1") w = BigDecimal::new("1") t = BigDecimal::new("956") while (u.exponent >= exp ) t,r = t.div(m57121,sig) u,r = t.div(k,sig) pi = pi + u k = k+two end pi end if \$0 == __FILE__ if ARGV.size == 1 print "PAI("+ARGV[0]+"):\n" p pai(ARGV[0].to_i) else print "TRY: ruby pai.rb 1000 \n" end end ``````