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bmaggi/AddMultAssociativityLimit.scala

Created October 15, 2018 11:34
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In scala floating addition/multiplication are commutative but not associative with big numbers
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AddMultAssociativityLimit.scala
// floating addition/multiplication are commutative but not associative with big numbers
val small = 1e-200
val big = 1e200
val invBig = -big
(big +invBig)+small // Double = 1.0E-200
big+(invBig+small) // Double = 0.0
List(big,invBig,small).reduceLeft(_+_) // Double = 1.0E-200
List(big,invBig,small).reduceRight(_+_) // Double = 0.0
(small*big)*big // Double = 1.0E200
small*(big*big) // Double = Infinity
List(small,big,big).reduceLeft(_*_) // Double = 1.0E200
List(small,big,big).reduceRight(_*_) // Double = Infinity
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