comment on

I was surprised to find out that 27**(1/3) == int 27**(1/3) and tried to introspect what the double float in the NV contains. I spend hours fiddling with printf , pack , unpack and (worst) the bit-order on intel processors to create this

(compare https://bartaz.github.io/ieee754-visualization/ )

$ perl
printf "%5s %.13a\n      %s\n", $_, eval($_), unpack("B*",pack("F>",ev
+al $_)) for qw(1 -1 2 -2 1/3 -1/3)
__END__
    1 0x1.0000000000000p+0
      0011111111110000000000000000000000000000000000000000000000000000
   -1 -0x1.0000000000000p+0
      1011111111110000000000000000000000000000000000000000000000000000
    2 0x1.0000000000000p+1
      0100000000000000000000000000000000000000000000000000000000000000
   -2 -0x1.0000000000000p+1
      1100000000000000000000000000000000000000000000000000000000000000
  1/3 0x1.5555555555555p-2
      0011111111010101010101010101010101010101010101010101010101010101
 -1/3 -0x1.5555555555555p-2
      1011111111010101010101010101010101010101010101010101010101010101
[download]

2 questions:

I wasn't able yet to make unpack "B1B11B52" work to distinguish between sign, exp and significant (mantissa), because of some byte alignment problems bits were missing at the end
Does this work on other builds and platforms too? ubuntu 64bit perl intel processor

  Platform:
    osname=linux
    osvers=6.1.0
    archname=x86_64-linux-gnu-thread-multi
  Compiler:
    cc='x86_64-linux-gnu-gcc'
[download]

update

tested on my ARM mobile which has another endianess, and got the same result

Cheers Rolf
_{(addicted to the Perl Programming Language :)

see Wikisyntax for the Monastery}

In reply to Introspection into floats/NV by LanX

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