/
sameq.go
48 lines (42 loc) · 1.46 KB
/
sameq.go
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package expreduce
import "math"
func IsSameQ(a Ex, b Ex, cl *CASLogger) bool {
aFlt, aIsFlt := a.(*Flt)
bFlt, bIsFlt := b.(*Flt)
_, aIsInteger := a.(*Integer)
_, bIsInteger := b.(*Integer)
_, aIsString := a.(*String)
_, bIsString := b.(*String)
_, aIsSymbol := a.(*Symbol)
_, bIsSymbol := b.(*Symbol)
_, aIsRational := a.(*Rational)
_, bIsRational := b.(*Rational)
_, aIsComplex := a.(*Complex)
_, bIsComplex := b.(*Complex)
_, aIsExpression := a.(*Expression)
_, bIsExpression := b.(*Expression)
if (aIsFlt && bIsFlt) || (aIsString && bIsString) || (aIsInteger && bIsInteger) || (aIsSymbol && bIsSymbol) || (aIsRational && bIsRational) || (aIsComplex && bIsComplex) {
// a and b are identical raw types
if aIsFlt && bIsFlt {
// This is important, without it e.g. NestWhileList[(# + 3/#)/2 &, 1.0, UnsameQ, 2] never converges
// https://stackoverflow.com/questions/46136886/comparing-floats-by-ignoring-last-bit-in-golang
aVal, _ := aFlt.Val.Float64()
bVal, _ := bFlt.Val.Float64()
if math.IsInf(aVal, 0) || math.IsInf(bVal, 0) {
return a.IsEqual(b, cl) == "EQUAL_TRUE"
} else {
return almostEqual(aVal, bVal)
}
} else {
return a.IsEqual(b, cl) == "EQUAL_TRUE"
}
} else if aIsExpression && bIsExpression {
return a.Hash() == b.Hash()
}
// This should never happen
return false
}
func almostEqual(a, b float64) bool {
ai, bi := int64(math.Float64bits(a)), int64(math.Float64bits(b))
return a == b || -1 <= ai-bi && ai-bi <= 1
}