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Re^2: Exploring IEEE754 floating point bit patterns.

by BrowserUk (Pope)
on Jul 29, 2012 at 03:11 UTC ( #984255=note: print w/ replies, xml ) Need Help??


in reply to Re: Exploring IEEE754 floating point bit patterns.
in thread Exploring IEEE754 floating point bit patterns.

Too bad my perl isn't compiled for 64 bits.

Try this version:

#! perl -slw use strict; use constant { POS_ZERO => '0'.'00000000000'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000000', POS_DENORM_1ST => '0'.'00000000000'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000001', POS_DENORM_LST => '0'.'00000000000'.'1111'.'11111111'.'11111111'.'111 +11111'.'11111111'.'11111111'.'11111111', POS_NORM_1ST => '0'.'00000000001'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000000', POS_NORM_LST => '0'.'11111111110'.'1111'.'11111111'.'11111111'.'111 +11111'.'11111111'.'11111111'.'11111111', POS_INF => '0'.'11111111111'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000000', POS_SNAN_1ST => '0'.'11111111111'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000001', POS_SNAN_LST => '0'.'11111111111'.'0111'.'11111111'.'11111111'.'111 +11111'.'11111111'.'11111111'.'11111111', POS_QNAN_1ST => '0'.'11111111111'.'1000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000000', POS_QNAN_LST => '0'.'11111111111'.'1111'.'11111111'.'11111111'.'111 +11111'.'11111111'.'11111111'.'11111111', NEG_ZERO => '1'.'00000000000'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000000', NEG_DENORM_1ST => '1'.'00000000000'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000001', NEG_DENORM_LST => '1'.'00000000000'.'1111'.'11111111'.'11111111'.'111 +11111'.'11111111'.'11111111'.'11111111', NEG_NORM_1ST => '1'.'00000000001'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000000', NEG_NORM_LST => '1'.'11111111110'.'1111'.'11111111'.'11111111'.'111 +11111'.'11111111'.'11111111'.'11111111', NEG_INF => '1'.'11111111111'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000000', NEG_SNAN_1ST => '1'.'11111111111'.'0000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000001', NEG_SNAN_LST => '1'.'11111111111'.'0111'.'11111111'.'11111111'.'111 +11111'.'11111111'.'11111111'.'11111111', NEG_IND => '1'.'11111111111'.'1000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000000', NEG_QNAN_1ST => '1'.'11111111111'.'1000'.'00000000'.'00000000'.'000 +00000'.'00000000'.'00000000'.'00000001', NEG_QNAN_LST => '1'.'11111111111'.'1111'.'11111111'.'11111111'.'111 +11111'.'11111111'.'11111111'.'11111111', }; sub bitsToDouble{ unpack 'd', pack 'b64', scalar reverse $_[0] } sub bitsToInts{ reverse unpack 'VV', pack 'b64', scalar reverse $_[0 +] } printf "%23.16g : %08x%08x\n", bitsToDouble( $_ ), bitsToInts( $_ ) for POS_ZERO, POS_DENORM_1ST, POS_DENORM_LST, POS_NORM_1ST, POS_NORM_L +ST, POS_INF, POS_SNAN_1ST, POS_SNAN_LST, POS_QNAN_1ST, POS_QNAN_LST, NEG_ZERO, NEG_DENORM_1ST, NEG_DENORM_LST, NEG_NORM_1ST, NEG_NORM_L +ST, NEG_INF, NEG_SNAN_1ST, NEG_SNAN_LST, NEG_IND, NEG_QNAN_1ST, NEG_QNAN_LST;

Outputs:

C:\test>\perl32\bin\perl ieee-32b.pl 0 : 0000000000000000 4.940656458412465e-324 : 0000000000000001 2.225073858507201e-308 : 000fffffffffffff 2.225073858507201e-308 : 0010000000000000 1.797693134862316e+308 : 7fefffffffffffff 1.#INF : 7ff0000000000000 1.#QNAN : 7ff0000000000001 1.#QNAN : 7ff7ffffffffffff 1.#QNAN : 7ff8000000000000 1.#QNAN : 7fffffffffffffff -0 : 8000000000000000 -4.940656458412465e-324 : 8000000000000001 -2.225073858507201e-308 : 800fffffffffffff -2.225073858507201e-308 : 8010000000000000 -1.797693134862316e+308 : ffefffffffffffff -1.#INF : fff0000000000000 -1.#QNAN : fff0000000000001 -1.#QNAN : fff7ffffffffffff -1.#IND : fff8000000000000 -1.#QNAN : fff8000000000001 -1.#QNAN : ffffffffffffffff

Seems that the compiler used to build AS 5.8.9 didn't distinguish between SNaN & QNaN. But the oddball -1.#IND was there. Perhaps its presence in the current compiler is legacy code.

The C version above should compile fine for 32-bit.


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Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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The start of some sanity?


Comment on Re^2: Exploring IEEE754 floating point bit patterns.
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Re^3: Exploring IEEE754 floating point bit patterns.
by roboticus (Canon) on Jul 29, 2012 at 04:15 UTC

    BrowserUk:

    That one worked nicely:

    marco@Boink:~ $ perl 984255_bitvec_floats_2.pl 0 : 0000000000000000 4.940656458412465e-324 : 0000000000000001 2.225073858507201e-308 : 000fffffffffffff 2.225073858507201e-308 : 0010000000000000 1.797693134862316e+308 : 7fefffffffffffff inf : 7ff0000000000000 nan : 7ff0000000000001 nan : 7ff7ffffffffffff nan : 7ff8000000000000 nan : 7fffffffffffffff -0 : 8000000000000000 -4.940656458412465e-324 : 8000000000000001 -2.225073858507201e-308 : 800fffffffffffff -2.225073858507201e-308 : 8010000000000000 -1.797693134862316e+308 : ffefffffffffffff -inf : fff0000000000000 -nan : fff0000000000001 -nan : fff7ffffffffffff -nan : fff8000000000000 -nan : fff8000000000001 -nan : ffffffffffffffff

    ...roboticus

    When your only tool is a hammer, all problems look like your thumb.

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