Split a character string based on change of character: Difference between revisions

From Rosetta Code
Content added Content deleted
(Undo revision 240798 by Hout (talk))
Line 24: Line 24:
<br><br>
<br><br>


=={{header|Haskell}}==
=={{header|AppleScript}}==
{{Trans|JavaScript}}
{{Trans|JavaScript}}
<lang AppleScript>on run
<lang AppleScript>on run
Line 151: Line 151:
end if
end if
end tail</lang>
end tail</lang>

{{Out}}
<pre>g, HHH, 5, YY, ++, ///, \</pre>

=={{header|Haskell}}==

<lang Haskell>import Data.List (group, intercalate)

main :: IO ()
main = putStrLn $ intercalate ", " (group "gHHH5YY++///\\")</lang>


{{Out}}
{{Out}}

Revision as of 14:13, 31 December 2016

Split a character string based on change of character is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
Task

Split a (character) string into comma (plus a blank) delimited strings based on a change of character   (left to right).

Show the output here   (use the 1st example below).


Blanks should be treated as any other character   (except they are problematic to display clearly).   The same applies to commas.


For instance, the string:

 gHHH5YY++///\ 

should be split and show:

 g, HHH, 5, YY, ++, ///, \ 



AppleScript

Translation of: JavaScript

<lang AppleScript>on run

   intercalate(", ", ¬
       map(curry(intercalate)'s lambda(""), ¬
           group("gHHH5YY++///\\")))
   
   --> "g, HHH, 5, YY, ++, ///, \\"
   

end run


-- GENERIC FUNCTIONS

-- group :: Eq a => [a] -> a on group(xs)

   script eq
       on lambda(a, b)
           a = b
       end lambda
   end script
   
   groupBy(eq, xs)

end group

-- groupBy :: (a -> a -> Bool) -> [a] -> a on groupBy(f, xs)

   set lng to length of xs
   if lng > 0 then
       set x to item 1 of xs
       set mf to mReturn(f)
       
       script furtherMatch
           on lambda(y)
               mf's lambda(x, y)
           end lambda
       end script
       
       set {ys, zs} to span(furtherMatch, tail(xs))
       set lstGroup to {{x} & ys}
       
       if zs ≠ {} then
           lstGroup & groupBy(mf, zs)
       else
           lstGroup
       end if
   else
       {}
   end if

end groupBy

-- Span of unbroken predicate matches at left, returned with remainder -- span :: (a -> Bool) -> [a] -> ([a],[a]) on span(f, xs)

   set lng to length of xs
   set i to 0
   tell mReturn(f)
       repeat while i < lng and lambda(item (i + 1) of xs)
           set i to i + 1
       end repeat
   end tell
   
   if i > 0 then
       if i < lng then
           {items 1 thru i of xs, (items (i + 1) thru -1 of xs)}
       else
           {xs, {}}
       end if
   else
       {{}, xs}
   end if

end span

-- intercalate :: Text -> [Text] -> Text on intercalate(strText, lstText)

   set {dlm, my text item delimiters} to {my text item delimiters, strText}
   set strJoined to lstText as text
   set my text item delimiters to dlm
   return strJoined

end intercalate

-- map :: (a -> b) -> [a] -> [b] on map(f, xs)

   tell mReturn(f)
       set lng to length of xs
       set lst to {}
       repeat with i from 1 to lng
           set end of lst to lambda(item i of xs, i, xs)
       end repeat
       return lst
   end tell

end map

-- curry :: (Script|Handler) -> Script on curry(f)

   script
       on lambda(a)
           script
               on lambda(b)
                   lambda(a, b) of mReturn(f)
               end lambda
           end script
       end lambda
   end script

end curry

-- Lift 2nd class handler function into 1st class script wrapper -- mReturn :: Handler -> Script on mReturn(f)

   if class of f is script then
       f
   else
       script
           property lambda : f
       end script
   end if

end mReturn

-- tail :: [a] -> [a] on tail(xs)

   if length of xs > 1 then
       items 2 thru -1 of xs
   else
       {}
   end if

end tail</lang>

Output:
g, HHH, 5, YY, ++, ///, \

Haskell

<lang Haskell>import Data.List (group, intercalate)

main :: IO () main = putStrLn $ intercalate ", " (group "gHHH5YY++///\\")</lang>

Output:
g, HHH, 5, YY, ++, ///, \

JavaScript

Translation of: Haskell

ES6

<lang JavaScript>(() => {

   'use strict';
   // GENERIC FUNCTIONS
   // group :: Eq a => [a] -> a
   const group = xs => groupBy((a, b) => a === b, xs);
   // groupBy :: (a -> a -> Bool) -> [a] -> a
   const groupBy = (f, xs) => {
       const lng = xs.length;
       if (lng > 0) {
           const x = xs[0],
               lstSpanRest = span(y => f(x, y), xs.slice(1)),
               ys = lstSpanRest[0],
               zs = lstSpanRest[1],
               group = [(ys.length ? [x].concat(ys) : [x])];
           return zs.length ? group.concat(groupBy(f, zs)) : group;
       } else return [];
   };
   // Span of unbroken predicate matches at left, returned with remainder
   //  span :: (a -> Bool) -> [a] -> ([a],[a])
   const span = (f, xs) => {
       for (var i = 0, lng = xs.length;
           (i < lng) && f(xs[i]); i++) {}
       return [xs.slice(0, i), xs.slice(i)];
   }
   // intercalate :: String -> [a] -> String
   const intercalate = (s, xs) => xs.join(s);


   // TEST
   return intercalate(", ", group("gHHH5YY++///\\".split())
       .map(x => x.join()));
   // -> "g, HHH, 5, YY, ++, ///, \\"

})();</lang>

Output:
g, HHH, 5, YY, ++, ///, \

Python

<lang python>import itertools

try: input = raw_input except: pass

s = input() groups = [] for _, g in itertools.groupby(s):

   groups.append(.join(g))

print(' input string: %s' % s) print(' output string: %s' % ', '.join(groups))</lang>

Output:

  when using the default input

      input string:  gHHH5YY++///\
     output string:  g, HHH, 5, YY, ++, ///, \

REXX

<lang rexx>/*REXX program splits a string based on change of character ───► a comma delimited list.*/ parse arg str . /*obtain optional arguments from the CL*/ if str== | str=="," then str= 'gHHH5YY++///\' /*Not specified? Then use the default.*/ p=left(str, 1) /*placeholder for the "previous" string*/ $= /* " " " output " */

     do j=1  for length(str);      @=substr(str, j, 1)    /*obtain a char from string. */
     if @\==left(p, 1)   then do;  $=$',' @;  p=;  end    /*different then previous?   */
                         else      $=$ || @               /*a replicated character.    */
     p=p || @                                             /*append char to current list*/
     end   /*j*/

say ' input string: ' str say ' output string: ' $ /*stick a fork in it, we're all done. */</lang> output   when using the default input:

      input string:  gHHH5YY++///\
     output string:  g, HHH, 5, YY, ++, ///, \