How to convert a floating point number to a 64 bit integer?

[SamL]

I need to convert a floating point number to a 64 bit integer (long
long). How to do that in perl? Thanks.

 

[SamL]

You will need to specify a little more about where these numbers are
coming from. Probably you want perldoc -f pack.

Ben

The number comes from calculation. For example:

my $a = 2.0**37;

Here I cannot use 2**37 directly since the result is -1.

I have found a way to "convert" it although I think there should be a
better way:

my $b = sprintf ("%.0f", $a);

 

[smallpond]

The number comes from calculation. For example:

my $a = 2.0**37;

Here I cannot use 2**37 directly since the result is -1.

I have found a way to "convert" it although I think there should be a
better way:

my $b = sprintf ("%.0f", $a);

use bigint;
$a = 2.0**37;
print int($a),"\n";

137438953472

 

[Peter J. Holzer]

That was my interpretation of the question, too. But it seems I was
mistaken.


The result of this is a string, not a 64 bit integer.

use bigint;
$a = 2.0**37;
print int($a),"\n";

137438953472

And the result of this is a bigint, which is also not the same as a 64
bit integer.

Perl can also be compiled to use 64 bit integers on most platforms.

But the real question is: What is the 64 bit integer for? Until
this is known, there is no way to tell whether a real 64 bit int is
needed or string or a bigint (or
maybe even a float) can be used instead.

hp

 

[SamL]

That was my interpretation of the question, too. But it seems I was
mistaken.


The result of this is a string, not a 64 bit integer.



And the result of this is a bigint, which is also not the same as a 64
bit integer.

Perl can also be compiled to use 64 bit integers on most platforms.

But the real question is: What is the 64 bit integer for? Until
this is known, there is no way to tell whether a real 64 bit int is
needed or  string or a bigint (or
maybe even a float) can be used instead.

        hp

Sorry, I did not make it clear. Actually I just need a string which is
the result of 2.0**37. So the simplest solution, as Ben said, is

perl -le'print 2.0**37'

That solved my problem. Thanks.