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Rev 84815 Rev 89319
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R Under development (unstable) (2022-03-19 r81942) -- "Unsuffered Consequences"
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R Under development (unstable) (2026-01-21 r89314) -- "Unsuffered Consequences"
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Copyright (C) 2022 The R Foundation for Statistical Computing
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Copyright (C) 2026 The R Foundation for Statistical Computing
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Platform: x86_64-pc-linux-gnu (64-bit)
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Platform: x86_64-pc-linux-gnu
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R is free software and comes with ABSOLUTELY NO WARRANTY.
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R is free software and comes with ABSOLUTELY NO WARRANTY.
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You are welcome to redistribute it under certain conditions.
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You are welcome to redistribute it under certain conditions.
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Type 'license()' or 'licence()' for distribution details.
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Type 'license()' or 'licence()' for distribution details.
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[11] 1.000000e-314 1.000000e-313 1.000000e-312 1.000000e-311 1.000000e-310
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[11] 1.000000e-314 1.000000e-313 1.000000e-312 1.000000e-311 1.000000e-310
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[16] 1.000000e-309 1.000000e-308 1.000000e-307
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[16] 1.000000e-309 1.000000e-308 1.000000e-307
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>
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>
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> # IEC60559 mandates this, but C99/C11 do not.
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> # IEC60559 mandates this, but C99/C11 do not.
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> # Mingw-w64 did not do so in v 2.0.1
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> # Mingw-w64 did not do so in v 2.0.1
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> x <- 0*(-1) # negative zero
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> (x <- 0*(-1)) # negative zero (prints as '0' in R on purpose!)
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> sqrt(x)
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[1] 0
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[1] 0
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> rt_0 <- sqrt(x) # ditto  -- but sprintf() shows "-0" :
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> sprintf("%g, rt = %g, .^2 = %g", x, sqrt(x), x^2)
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> sprintf("%g, rt = %g, .^2 = %g", x, sqrt(x), x^2)
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[1] "-0, rt = -0, .^2 = 0"
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[1] "-0, rt = -0, .^2 = 0"
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> stopifnot(exprs = {
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> identical(x, sqrt(x))
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+    identical(1/ x, -Inf)
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+    identical(1/-x, +Inf)
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+    identical(x, -x,) # default num.eq=TRUE  ==> -0 "identical" 0
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+    ! identical(x, -x,    num.eq=FALSE) # but not bitwise identical
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+    identical(x, sqrt(x), num.eq=FALSE) # sqrt(-0) == -0
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+    identical(-x, x^2,    num.eq=FALSE) # (-0)^2   == +0 = --0
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[1] TRUE
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+ })
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>
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>