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Programming-Idioms

  • Python
  • Pascal

Idiom #219 Replace multiple spaces with single space

Create the string t from the value of string s with each sequence of spaces replaced by a single space.

Explain if only the space characters will be replaced, or the other whitespaces as well: tabs, newlines.

uses sysutils;
  t := s;
  while Pos('  ',t) > 0 do
    t := StringReplace(t, '  ', ' ', [rfReplaceAll]);

Only removes double spaces.
StringReplace is not recursive, hence the loop.
var
  i, j: integer;
  t,s: string;
const
  whitespace = [#32,#13,#10,#9];
begin
  ....
  t := '';
  j := 0;
  setlength(t, length(s));
  for i := 1 to length(s) do
    if not ((s[i] in whitespace) and 
            ((i < length(s)) and (s[i+1] in whitespace))) then
    begin
      inc(j);
      t[j] := s[i];
    end;
  setlength(t,j);
end.

Removes all double whitespace.
Using setlength twice and accessing individual characters of the result is faster than adding characters one at a time.
More elaborate, but faster than the RegEx and StringReplace solutions.
regexpr
  t := ReplaceRegExpr('\s+',s,' ',False);

Yes, you can do it with a RegEx as well.
Removes all double whitespace.
t: str = " ".join(s.split())

Splits s into a list based on whitespace, then joins them together again
import re
t = re.sub(' +', ' ', s)

Only replaces spaces.
from re import split
t = ' '.join(split(' {2,}', s))
from re import split
t = ' '.join(split(r'\s{2,}', s))
(def t (clojure.string/replace s #"\s+" " "))
New implementation...
< > ⌨
programming-idioms.org 
  t := s;
  while Pos('  ',t) > 0 do
    t := StringReplace(t, '  ', ' ', [rfReplaceAll]);

var
  i, j: integer;
  t,s: string;
const
  whitespace = [#32,#13,#10,#9];
begin
  ....
  t := '';
  j := 0;
  setlength(t, length(s));
  for i := 1 to length(s) do
    if not ((s[i] in whitespace) and 
            ((i < length(s)) and (s[i+1] in whitespace))) then
    begin
      inc(j);
      t[j] := s[i];
    end;
  setlength(t,j);
end.
  t := ReplaceRegExpr('\s+',s,' ',False);
t: str = " ".join(s.split())
t = re.sub(' +', ' ', s)
t = ' '.join(split(' {2,}', s))
t = ' '.join(split(r'\s{2,}', s))
(def t (clojure.string/replace s #"\s+" " "))
auto t = s;
t.erase(std::ranges::unique(t, 
  [](char const &lhs,char const &rhs)
  { return lhs == rhs && ::std::iswspace(lhs); }
).begin(), t.end());
string t = Regex.Replace(s, @"\s+", " ");
string t = Regex.Replace(s, " +", " ");
var t = s.replaceAll(RegExp(r"\s+"), " ");
singleSpace(Text) ->
        singleSpace(0, Text).

singleSpace(_, []) -> [];
singleSpace(32, [32 | Rest]) ->
        singleSpace(32, Rest);
singleSpace(32, [Ch | Rest]) ->
        [Ch] ++ singleSpace(Ch,  Rest);
singleSpace(Last, [Ch | Rest]) ->
                [Ch] ++ singleSpace(Ch, Rest).


%%singleSpace("this is  a      text  with        multiple spaces").
whitespaces := regexp.MustCompile(`\s+`)
t := whitespaces.ReplaceAllString(s, " ")
def t = s.replaceAll(/\s+/, ' ')
t= unwords $ words s
let t = s.replace(/\s+/g, ' ');
let t = s.replaceAll(/\s{2,}/g, '')
let t = s.replaceAll(/ {2,}/g, '')
String t = s.replaceAll(" +", " ");
String t = join(" ", s.split(" +", -1));
String t = s.replaceAll("\\s+", " ");
String t = s.replaceAll(" {2,}", " ");
(defun words (str)
  (if (equalp str "") nil 
      (let ((p (position #\Space str )))
    (cond ((null p) (list str))
          ((zerop p ) (words (subseq str 1)))
          (T (cons (subseq str 0 p) (words (subseq str (+ 1 p ))))))))) 

(setf s " aa  bbb  cc1 ")

 (let ((ws (words s )))
   (setf t (car ws))
   (dolist (w (cdr ws ))
     (setf t (concatenate 'string t " " w ))))
 (print t)
 
local t = s:gsub("%s+", " ")
$t = $s;
do $t = str_replace('  ', ' ', $t, $count); while($count);
$t = preg_replace('/\s+/', ' ', $s);
my $t = $s;
$t =~ s/\s+/ /g;
my $t = $s;
$t =~ s/ +/ /g;
t = s.squeeze(" ")
let re = Regex::new(r"\s+").unwrap();
let t = re.replace_all(s, " ");
Dim t As String = Regex.Replace(s, "\s+", " ")
Dim t As String = Regex.Replace(s, " +", " ")