convert string to number?

2006-07-07 Thread Adam Witney 

Hi,

I have a problem where a number read from a file is being treated as a
string by perl (I think!). I am using the module RSPerl which is an
interface between Perl and the statistical language R. When i read a
column of numbers from a file and pass it to the perl/R function i get
an invalid 'type' (character) of argument error.

The reason i think this is a problem on the Perl side is shown by this
pseudocode:

while(FILE){
   ... stuff to extract $value from each row ...

   push(@list1, $value);
}

@list2 = (100.2, 232.333, 344.2);   # these are the numbers from file

my_R_func_call([EMAIL PROTECTED]);
my_R_func_call([EMAIL PROTECTED]);

using @list1 gives the error, @list2 does not. if i add a line that
performs a redundant mathematical operation on $value before push'ing it
into @list1 eg

   if($value  1){}
   push(@list1, $value);

then the error goes away, therefore i suspect this is a problem with the
internal datatype. I have never worried about this in Perl before, but
it appears to be more important now as R is more strict.

is there a way in Perl to force a variable to be a number rather than a
string?

thanks

adam

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Re: convert string to number?

2006-07-07 Thread Paul McCann 

Hi Adam,

sounds like the symptoms you'd get if the value you're sending to R  
has a newline character hanging on the end. Perl will do the  
conversion to an integer when required [1], but if you're passing  
such a thing to R it'll probably get grumpy. Just chomp the line  
before doing the extraction of the values and with any luck all will  
be well.


[1] For example...

#!/usr/bin/perl
use warnings;
use strict;
my $string=98\n;
my $sub=$string-10;
print OK we now have $sub\n;

= OK we now have 88

Cheers,
Paul

Re: convert string to number?

2006-07-07 Thread Dominic Dunlop 

On 2006–07–07, at 10:18, Adam Witney wrote:

is there a way in Perl to force a variable to be a number rather  
than a

string?


Yes. You already discovered it: perform a redundant mathematical  
operation on it. The usual idiom is to add zero to it. (Conversely,  
to force something to be a string, append an empty string to it.)


What's happening internally is that (among other things), perl  
variables can accommodate for both string and numeric representations  
of the variable's value, but they're filled in lazily: a string is  
not converted to a number until the variable is used in a numeric  
context (and vice versa). Despite this laziness, Perl is usually able  
to do what you mean as far as numbers and strings are concerned, but  
sometimes you have to give it a hint. For more information, see the  
perlnumber man page.

--
Dominic Dunlop

Updates for Mac-Carbon, Mac-Glue, etc.

2006-07-07 Thread Chris Nandor 
Last night I released new Mac-Carbon, Mac-AppleEvents-Simple, and Mac-Glue
updates, mostly for endian fixes for typeAbsoluteOrdinal values (such as
gFirst, gAny) and typeLongDateTime values (which are quads).

I also added a new function to Mac::Speech, to direct speech output to an
AIFF file instead of the speakers, which I am using for my online radio
show (podcast to some of you), where I generate questions from people
using speech synthesis (http://pudge.net/ask/).

-- 
Chris Nandor  [EMAIL PROTECTED]http://pudge.net/
Open Source Technology Group   [EMAIL PROTECTED] http://ostg.com/