Removing spaces between single letters

Question

I have a string that may contain an arbitrary number of single-letters separated by spaces. I am looking for a regex (in Perl) that will remove spaces between all (unknown n

Answer 1

This will do the job.

(?<=\b\w)\s(?=\w\b)

Answer 2

This piece of code

#!/usr/bin/perl

use strict;

my @strings = ('a b c', 'ab c d', 'a bcd e f gh', 'abc d');

foreach my $string (@strings) {
   print "$string --> ";
   $string =~ s/\b(\w)\s+(?=\w\b)/$1/g; # the only line that actually matters
   print "$string\n";
}

prints this:

a b c --> abc
ab c d --> ab cd
a bcd e f gh --> a bcd ef gh
abc d --> abc d

I think/hope this is what you're looking for.

Answer 3

Hi I have written simple javascript to do this it's simple and you can convert into any language.

function compressSingleSpace(source){

    let words = source.split(" ");
		let finalWords = [];
		let tempWord = "";

		for(let i=0;i<words.length;i++){

			if(tempWord!='' && words[i].length>1){
				finalWords.push(tempWord);
				tempWord = '';
			}

			if(words[i].length>1){
				finalWords.push(words[i]);
			}else{
				tempWord += words[i];
			}

		}

		if(tempWord!=''){
			finalWords.push(tempWord);
		}

		source = finalWords.join(" ");
    
    return source;

}


function convertInput(){
  let str = document.getElementById("inputWords").value;
  document.getElementById("firstInput").innerHTML = str;
  
  let compressed = compressSingleSpace(str);
    document.getElementById("finalOutput").innerHTML = compressed;
}

label{
    font-size:20px;
    margin:10px;
}
input{
    margin:10px;
    font-size:15px;
    padding:10px;
}

input[type="button"]{
  cursor:pointer;
  background: #ccc;
}

#firstInput{
  color:red;
  font-size:20px;
  margin:10px;
}

#finalOutput{
  color:green;
  font-size:20px;
  margin:10px;
}

<label for="inputWords">Enter your input and press Convert</label><br>
<input id="inputWords" value="check this site p e t z l o v e r . c o m thanks">
<input type="button" onclick="convertInput(this.value)" value="Convert" >
<div id="firstInput">check this site p e t z l o v e r . c o m thanks</div>
<div id="finalOutput">check this site petzlover.com thanks</div>

Answer 4

It's not a regex but since I am lazy by nature I would it do this way.

#!/usr/bin/env perl
use warnings;
use 5.012;

my @strings = ('a b c', 'ab c d', 'a bcd e f gh', 'abc d');
for my $string ( @strings ) {
    my @s; my $t = '';
    for my $el ( split /\s+/, $string ) {
        if ( length $el > 1 ) {
        push @s, $t if $t;
        $t = '';
        push @s, $el;
        } else { $t .= $el; }
    }
    push @s, $t if $t;
    say "@s";
}

OK, my way is the slowest:

no_regex   130619/s         --       -60%       -61%       -63%
Alan_Moore 323328/s       148%         --        -4%        -8%
Eric_Storm 336748/s       158%         4%         --        -5%
canavanin  352654/s       170%         9%         5%         --

I didn't include Ether's code because ( as he has tested ) it returns different results.

Answer 5

Your description doesn't really match your examples. It looks to me like you want to remove any space that is (1) preceded by a letter which is not itself preceded by a letter, and (2) followed by a letter which is not itself followed by a letter. Those conditions can be expressed precisely as nested lookarounds:

/(?<=(?<!\pL)\pL) (?=\pL(?!\pL))/

tested:

use strict;
use warnings;

use Test::Simple tests => 4;

sub clean {
  (my $x = shift) =~ s/(?<=(?<!\pL)\pL) (?=\pL(?!\pL))//g;
  $x;
}

ok(clean('ab c d')        eq 'ab cd');
ok(clean('a bcd e f gh')  eq 'a bcd ef gh');
ok(clean('a b c')         eq 'abc');
ok(clean('ab c d')        eq 'ab cd');

output:

1..4
ok 1
ok 2
ok 3
ok 4

I'm assuming you really meant one space character (U+0020); if you want to match any whitespace, you might want to replace the space with \s+.

Answer 6

Now I have the slowest and the fastest.

#!/usr/bin/perl
use 5.012;
use warnings;
use Benchmark qw(cmpthese);
my @strings = ('a b c', 'ab c d', 'a bcd e f gh', 'abc d');

cmpthese( 0, {
    Eric_Storm  => sub{ for my $string (@strings) { $string =~ s{\b(\w) ((?: \s+ (\w)\b)+)}{$1 . join '', split m|\s+|, $2}gex; } },
    canavanin   => sub{ for my $string (@strings) { $string =~ s/\b(\w)\s+(?=\w\b)/$1/g; } },
    Alan_Moore  => sub{ for my $string (@strings) { $string =~ s/(?<=(?<!\pL)\pL) (?=\pL(?!\pL))//g; } },
    keep_uni    => sub{ for my $string (@strings) { $string =~ s/\PL\pL\K (?=\pL(?!\pL))//g; } },
    keep_asc    => sub{ for my $string (@strings) { $string =~ s/[^a-zA-Z][a-zA-Z]\K (?=[a-zA-Z](?![a-zA-Z]))//g; } },
    no_regex    => sub{ for my $string (@strings) { my @s; my $t = ''; 
    for my $el (split /\s+/, $string) {if (length $el > 1) { push @s, $t if $t; $t = ''; push @s, $el; } else { $t .= $el; } }
    push @s, $t if $t;
    #say "@s";
    } },
});

.

           Rate  no_regex Alan_Moore Eric_Storm canavanin  keep_uni keep_asc                                                                                                                                                             
no_regex    98682/s        --       -64%       -65%      -66%      -81%     -87%                                                                                                                                                             
Alan_Moore 274019/s      178%         --        -3%       -6%      -48%     -63%                                                                                                                                                             
Eric_Storm 282855/s      187%         3%         --       -3%      -46%     -62%                                                                                                                                                             
canavanin  291585/s      195%         6%         3%        --      -45%     -60%
keep_uni   528014/s      435%        93%        87%       81%        --     -28%
keep_asc   735254/s      645%       168%       160%      152%       39%       --