How to avoid an alphabet and integer next to it in a string?

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

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Re: How to avoid an alphabet and integer next to it in a string? by VincentK (Beadle) on Mar 21, 2014 at 21:01 UTC
Hi piscean. I don't know much about chemistry, but I think I found a library that will help you. Chemistry::File::Formula - Molecular formula reader/formatter http://search.cpan.org/~itub/Chemistry-Mol-0.37/File/Formula.pm I plugged the library into a basic script and it seems to parse the elements out in the way you need. From here you should be able to parse each key/value in the formula hash and base your calcuation on the elements you need. I hope this helps. `use strict; use warnings; use Data::Dumper; use Chemistry::File::Formula; while(<DATA>) { chomp; my %formula = Chemistry::File::Formula->parse_formula("$_"); print "-" x 16, "\n"; print Dumper \%formula; print "-" x 16, "\n"; } __DATA__ C6H5OH C6H9 Hg` [download] Output: `C:\monks\calc_mass>perl calc_molecularmass.pl ---------------- $VAR1 = { 'H' => 6, 'O' => 1, 'C' => 6 }; ---------------- ---------------- $VAR1 = { 'H' => 9, 'C' => 6 }; ---------------- ---------------- $VAR1 = { 'Hg' => 1 }; ---------------- C:\monks\calc_mass>` [download]	[reply] [d/l] [select]
Re: How to avoid an alphabet and integer next to it in a string? by kcott (Archbishop) on Mar 21, 2014 at 20:01 UTC
G'day piscean, Welcome to the monastery. You can do that like this. The tests include one- and two-letter symbols with and without numbers. I'll leave you to replace my rough atomic weights with more precise ones. #!/usr/bin/env perl -l use strict; use warnings; my %weight = (C => 12, O => 16, Cl => 35.5); my %tests = ( phenol => ['C6H5OH', 6 * 12 + 1 * 16], chloroform => ['CHCl3', 1 * 12 + 3 * 35.5], ); for my $compound (keys %tests) { print '-' x 40; print "Compound: $compound"; my $formula = $tests{$compound}[0]; print "Formula: $formula"; my $calculated = 0; $formula =~ s{([A-Z][a-z]?)(\d)}{ exists $weight{$1} and $calculated += $weight{$1} ($2 \|\| 1) }eg; print "Expected: $tests{$compound}[1]"; print "Calculated: $calculated"; } [download] Output: `---------------------------------------- Compound: phenol Formula: C6H5OH Expected: 88 Calculated: 88 ---------------------------------------- Compound: chloroform Formula: CHCl3 Expected: 118.5 Calculated: 118.5` [download] -- Ken	[reply] [d/l] [select]
Re^2: How to avoid an alphabet and integer next to it in a string? by piscean (Acolyte) on Mar 21, 2014 at 20:46 UTC
Thanks Ken! It was really helpful :) I've used Chemistry::MolecularMass module to have precise atomic weights.	[reply]
Re^3: How to avoid an alphabet and integer next to it in a string? by kcott (Archbishop) on Mar 21, 2014 at 21:00 UTC
I haven't used Chemistry::MolecularMass previously (in fact, I wasn't aware of its existence until now); however, looking at its documentation, it would appear another (completely untested) solution would be: `use Chemistry::MolecularMass; my $mm = Chemistry::MolecularMass::->new(); $mm->replace_elements(H => 0); my $no_H_mass = $mm->calc_mass($your_formula);` [download] -- Ken	[reply] [d/l]
Re: How to avoid an alphabet and integer next to it in a string? by AnomalousMonk (Archbishop) on Mar 21, 2014 at 20:09 UTC
Maybe something like: `c:\@Work\Perl\monks>perl -wMstrict -le "my $Hn = qr{ H (?! [[:lower:]]) \d* }xms; my $not_Hn = qr{ (?! $Hn) }xms; ;; use constant FORMULA => 'HC6H5OHHg2HeBr3H'; ;; my $s = FORMULA; print qq{'$s'}; $s =~ s{ $Hn }''xmsg; print qq{'$s'}; ;; $s = FORMULA; my @elements = $s =~ m{ $not_Hn [[:upper:]] [[:lower:]]? \d* }xmsg; printf qq{'$_' } for @elements; " 'HC6H5OHHg2HeBr3H' 'C6OHg2HeBr3' 'C6' 'O' 'Hg2' 'He' 'Br3'` [download]	[reply] [d/l]
Re^2: How to avoid an alphabet and integer next to it in a string? by piscean (Acolyte) on Mar 21, 2014 at 20:43 UTC
Thanks! This helped too :)	[reply]
Re: How to avoid an alphabet and integer next to it in a string? by hippo (Archbishop) on Mar 21, 2014 at 17:53 UTC
I tried doing that, but I failed. What did you try? How did it fail? Hard to tell, but is all you are looking for this? `my $formula = 'C6H5OH'; $formula =~ s/H\d//g; print "$formula\n";` [download] Update: As runrig suggests below the more general `s/H\d*//g;` may be more appropriate to your needs.	[reply] [d/l] [select]
Re^2: How to avoid an alphabet and integer next to it in a string? by piscean (Acolyte) on Mar 21, 2014 at 17:57 UTC
Yes, this is what I was looking for. Thanks! I tried avoiding H in C6H9. It turned out to calculate C69 giving me a wrong result. Of course, I was foolish enough to try this.	[reply]
Re^3: How to avoid an alphabet and integer next to it in a string? by piscean (Acolyte) on Mar 21, 2014 at 18:02 UTC
`my $molform = <STDIN>; $molform =~ s/[^a-zA-G0-9]//g; my $molmass = new Chemistry::MolecularMass; my $mass = $molmass->calc_mass("$molform");` [download]	[reply] [d/l]
Re^4: How to avoid an alphabet and integer next to it in a string? by runrig (Abbot) on Mar 21, 2014 at 18:08 UTC
Re^5: How to avoid an alphabet and integer next to it in a string? by piscean (Acolyte) on Mar 21, 2014 at 18:16 UTC
Re^2: How to avoid an alphabet and integer next to it in a string? by piscean (Acolyte) on Mar 21, 2014 at 19:17 UTC
As runrig suggests below the more general s/H\d//g; may be more appropriate to your needs.* It does help, but what about Hg element? When I enter Hg, it gives me zero as output.	[reply]
Re^2: How to avoid an alphabet and integer next to it in a string? by piscean (Acolyte) on Mar 21, 2014 at 18:05 UTC
Oops! This is giving me wrong output too. Hope the code I posted below gives an idea of what I wanted.	[reply]
Re^3: How to avoid an alphabet and integer next to it in a string? by hazylife (Monk) on Mar 21, 2014 at 18:08 UTC
What about this? `$formula =~ s/H\d*//g;` [download]	[reply] [d/l]
Re^4: How to avoid an alphabet and integer next to it in a string? by moritz (Cardinal) on Mar 21, 2014 at 18:20 UTC
Re^5: How to avoid an alphabet and integer next to it in a string? by piscean (Acolyte) on Mar 21, 2014 at 18:38 UTC
Some notes below your chosen depth have not been shown here
Re^5: How to avoid an alphabet and integer next to it in a string? by hazylife (Monk) on Mar 21, 2014 at 18:29 UTC
Re^5: How to avoid an alphabet and integer next to it in a string? by DrHyde (Prior) on Mar 25, 2014 at 11:26 UTC
Re^4: How to avoid an alphabet and integer next to it in a string? by piscean (Acolyte) on Mar 21, 2014 at 18:12 UTC