Re: Perl binary file

After some digging, would this work?

print $out pack('f<',2.5) ; #single, little endian
print $out pack('d<',2.5) ; #double, little endian
print $out pack('f>',2.5) ; #single, big endian
print $out pack('d>',2.5) ; #single, big endian
[download]

Is there a diference between 'd' or 'D' (or 'f' and 'F')which can create incompatible issues? And as far the append, will it be sequencial?

Kind regards

Kepler

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Re^2: Perl binary file by soonix (Chancellor) on Dec 29, 2017 at 10:01 UTC
perldoc pack says `F` is "Perl internal format", perlpacktut under "Floating point Numbers" is a bit more helpful, but not very…	[reply] [d/l]
Re^2: Perl binary file by Anonymous Monk on Dec 31, 2017 at 09:35 UTC
'd' or 'D' These are C `double` and `long double`, respectively. They are probably different. On Intel machines, `long double` is usually an 80-bit non-IEEE754 type while `double` is standard IEEE-754 double precision type. 'f' and 'F' These are C `float` and "whatever Perl uses internally". Again, on Intel machines `float` usually represents IEEE-754 single precision type, while `NV` would be even less portable than `long double` (because a user could rebuild their Perl with different definition for `NV`) but priceless for exact data caching in between the runs of your own application. To answer your original question, use `f` for IEEE-754 single precision, `d` for IEEE-754 double precision types compatible with C and VB (if `float` and `double` do not correspond to IEEE types on a given system, chances are it doesn't support IEEE types at all and such processors are rare enough that you probably shouldn't worry about them) and > for big-endian (most significant byte first; "network byte order"), < for little-endian (least significant byte first; "Intel byte order"). Also, you were right, to sequentially append to binary files, just use `open (my $fh, ">>:raw", $filename);`.	[reply] [d/l] [select]