How to extract the first elemnet from an integer type value ???

sanjay nayak has asked for the wisdom of the Perl Monks concerning the following question:

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Re: How to extract the first elemnet from an integer type value ??? by b10m (Vicar) on Aug 31, 2006 at 08:58 UTC
`print substr($num, 0, 1);` [download] See substr -- b10m All code is usually tested, but rarely trusted.	[reply] [d/l]
Re: How to extract the first elemnet from an integer type value ??? by borisz (Canon) on Aug 31, 2006 at 09:07 UTC
or use a regex `print $num =~ /^(.)/;` [download] Boris	[reply] [d/l]
Re: How to extract the first elemnet from an integer type value ??? by GrandFather (Saint) on Aug 31, 2006 at 09:22 UTC
`my $digit = (split //, '100')[0];` [download] Update or `my $num = 100; my $digit = int ($num / 10 ** int (log ($num) / log(10)));` [download] DWIM is Perl's answer to Gödel	[reply] [d/l] [select]
Re^2: How to extract the first elemnet from an integer type value ??? by Leviathan (Scribe) on Aug 31, 2006 at 09:49 UTC
`my $num = 100; my $digit = int ($num / 10 ** (length($num)-1) );` [download] -- Leviathan	[reply] [d/l]
Re^3: How to extract the first elemnet from an integer type value ??? by GrandFather (Saint) on Aug 31, 2006 at 09:55 UTC
`my $num = 100; my $digit = int ($num / ('1' . ('0' x int (length ($num) -1))));` [download] DWIM is Perl's answer to Gödel	[reply] [d/l]
Re^4: How to extract the first elemnet from an integer type value ??? by Not_a_Number (Prior) on Aug 31, 2006 at 10:08 UTC
Re^5: How to extract the first elemnet from an integer type value ??? by GrandFather (Saint) on Aug 31, 2006 at 10:16 UTC
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Re^4: How to extract the first elemnet from an integer type value ??? by Leviathan (Scribe) on Aug 31, 2006 at 10:11 UTC
Re: How to extract the first elemnet from an integer type value ??? by prasadbabu (Prior) on Aug 31, 2006 at 09:18 UTC
`TIMTOWTDI $num = 100; print unpack('A', $num);` [download] Prasad	[reply] [d/l]
Re: How to extract the first elemnet from an integer type value ??? by vi_srikanth (Acolyte) on Aug 31, 2006 at 09:02 UTC
`print int ($num / 100); or print substr($num,0,1); or if ($num=~m/(.)/) {print $1}` [download]	[reply] [d/l]
Re: How to extract the first elemnet from an integer type value ??? by bart (Canon) on Aug 31, 2006 at 20:59 UTC
People are giving you lots of little recipes, without explaining how they work. The basic idea is this: In Perl, you can just use a number in a scalar as a string. Perl will convert it for you, from number to string, if necessary. So, all you have to do is extract the first character from the number treated as a string. That's what substr, unpack, the regex /^(.)/ all do.	[reply]
Re: How to extract the first elemnet from an integer type value ??? by GrandFather (Saint) on Aug 31, 2006 at 10:11 UTC
`$num -= 1;` [download] DWIM is Perl's answer to Gödel	[reply] [d/l]
Re: How to extract the first elemnet from an integer type value ??? by davido (Cardinal) on Aug 31, 2006 at 17:03 UTC
`print reverse($num)+0;` Dave	[reply] [d/l]
Re^2: How to extract the first elemnet from an integer type value ??? by Velaki (Chaplain) on Aug 31, 2006 at 17:08 UTC
Perhaps you meant this? `print reverse($num) % 10;` [download] Pax vobiscum et gratias vobis ago valeteque, -v "Perl. There is no substitute."	[reply] [d/l]
Re^3: How to extract the first elemnet from an integer type value ??? by davido (Cardinal) on Aug 31, 2006 at 18:28 UTC
No, I meant `print reverse($num)+0;`, which extracts '1' from the integer 100, as the OP asked. He didn't ask about 52, 583, 47, or 32767, he asked about 100. ;) Yours works too, of course. The difference being, yours works over any integer, and mine works for the integer 100, or any other integer where the leading digit contains a positive value and the subsequent digits are zero. But both extract 1 from 100. He may also have meant all integers, or he may also have meant any integer with one leading significant digit and all trailing digits being zero. Or he may have meant only the integer 100, or maybe an integer beginning with 1 and followed by only zeros, or maybe he meant only positive integers, or maybe something else entirely, but he said an integer, 100. Any other assertion is guesswork. Of course we're just having fun. Everyone knows the best way is this: `print shift @{[(split//,$num)[0-(@{[split//,$num]})]]}` [download]	[reply] [d/l] [select]
Re: How to extract the first elemnet from an integer type value ??? by mreece (Friar) on Aug 31, 2006 at 18:53 UTC
in the spirit of reverse-golf silly answers: `my $num = 100; my $extracted = do { open 0 and $_ = ( grep /my \$num = \d/, <0> )[0] +and /(\d)/; $1; };` [download]	[reply] [d/l]
Re: How to extract the first elemnet from an integer type value ??? by swampyankee (Parson) on Aug 31, 2006 at 21:05 UTC
`my $num = 100; print "First digit of $num is " . int($num / (10 ** int(log(abs($num)) +/log(10)))) . "\n";` [download] Make sure that some code is wrapped about it to make sure that you don't try to take log(0). log(10) is there because log is actually log_e, and log₁₀ is needed. emc Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. Albert Einstein	[reply] [d/l]