Reverse words in a string

From Rosetta Code
Revision as of 13:05, 13 April 2014 by rosettacode>Dkf (Clean up task description)
Reverse words in a string 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.

The task is to reverse the order of all tokens in each of a number of strings and display the result; the order of characters within a token should not be modified.

Example: “Hey you, Bub!” would be shown reversed as: “Bub! you, Hey”

Tokens are any non-space characters separated by spaces (formally, white-space); the visible punctuation forms part of the word within which it is located and should not be modified. You may assume that there are no significant non-visible characters in the input. Multiple or superfluous spaces may be compressed into a single space. Some strings have no tokens, so an empty string (or one just containing spaces) would be the result. Display the strings in order (1st, 2nd, 3rd, ···), and one string per line. (You can consider the ten strings as ten lines, and the tokens as words.)

Input data
             (ten lines within the box)
 line
     ╔════════════════════════════════════════╗
   1 ║  ---------- Ice and Fire ------------  ║
   2 ║                                        ║  ◄─── a blank line here.
   3 ║  fire, in end will world the say Some  ║
   4 ║  ice. in say Some                      ║
   5 ║  desire of tasted I've what From       ║
   6 ║  fire. favor who those with hold I     ║
   7 ║                                        ║  ◄─── a blank line here.
   8 ║  ... elided paragraph last ...         ║
   9 ║                                        ║  ◄─── a blank line here.
  10 ║  Frost Robert -----------------------  ║
     ╚════════════════════════════════════════╝

AWK

<lang AWK>

  1. syntax: GAWK -f REVERSE_WORDS_IN_A_STRING.AWK

BEGIN { 

   text[++i] = "---------- Ice and Fire ------------"
   text[++i] = ""
   text[++i] = "fire, in end will world the say Some"
   text[++i] = "ice. in say Some"
   text[++i] = "desire of tasted I've what From"
   text[++i] = "fire. favor who those with hold I"
   text[++i] = ""
   text[++i] = "... elided paragraph last ..."
   text[++i] = ""
   text[++i] = "Frost Robert -----------------------"
   leng = i
   for (i=1; i<=leng; i++) {
     n = split(text[i],arr," ")
     for (j=n; j>0; j--) {
       printf("%s ",arr[j])
     }
     printf("\n")
   }
   exit(0)

} </lang>

output:

------------ Fire and Ice ----------

Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.

... last paragraph elided ...

----------------------- Robert Frost

C

<lang c>#include <stdio.h>

  1. include <ctype.h>

void rev_print(char *s, int n) { 

       for (; *s && isspace(*s); s++);
       if (*s) {
               char *e;
               for (e = s; *e && !isspace(*e); e++);
               rev_print(e, 0);
               printf("%.*s%s", (int)(e - s), s, " " + n);
       }
       if (n) putchar('\n');

}

int main(void) { 

       char *s[] = {
               "---------- Ice and Fire ------------",
               "                                    ",
               "fire, in end will world the say Some",
               "ice. in say Some                    ",
               "desire of tasted I've what From     ",
               "fire. favor who those with hold I   ",
               "                                    ",
               "... elided paragraph last ...       ",
               "                                    ",
               "Frost Robert -----------------------",
               0
       };
       int i;
       for (i = 0; s[i]; i++) rev_print(s[i], 1);

       return 0;

}</lang> Output is the same as everyone else's.

D

<lang d>void main() { 

   import std.stdio, std.string, std.range;

   immutable text =

"---------- Ice and Fire ------------

fire, in end will world the say Some ice. in say Some desire of tasted I've what From fire. favor who those with hold I

... elided paragraph last ...

Frost Robert -----------------------"; 

   writefln("%(%-(%s %)\n%)",
            text.splitLines.map!(r => r.split.retro));

}</lang> The output is the same as the Python entry.

J

Treated interactively:

<lang J> ([:;@|.[:<;.1 ' ',]);._2]0 :0

Ice and Fire ------------ 

 fire, in end will world the say Some
 ice. in say Some
 desire of tasted I've what From
 fire. favor who those with hold I

  ... elided paragraph last ...

 Frost Robert -----------------------

) 

------------ Fire and Ice ----------  
                                      
Some say the world will end in fire,  
Some say in ice.                      
From what I've tasted of desire       
I hold with those who favor fire.     
                                      
... last paragraph elided ...         
                                      
----------------------- Robert Frost

</lang>

Perl 6

<lang>say .words.reverse for q:to/END/.lines;

Ice and Fire ------------

fire, in end will world the say Some ice. in say Some desire of tasted I've what From fire. favor who those with hold I

... elided paragraph last ...

Frost Robert ----------------------- END </lang>

Output:
------------ Fire and Ice ----------

Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.

... last paragraph elided ...

----------------------- Robert Frost

Python

<lang python>>>> text = \

Ice and Fire ------------

fire, in end will world the say Some ice. in say Some desire of tasted I've what From fire. favor who those with hold I

... elided paragraph last ...

Frost Robert ----------------------- >>> for line in text.split('\n'): print(' '.join(line.split()[::-1]))

Fire and Ice ----------

Some say the world will end in fire, Some say in ice. From what I've tasted of desire I hold with those who favor fire.

... last paragraph elided ...

Robert Frost

>>> </lang>

REXX

<lang rexx>/*REXX pgm reverses the order of tokens in a string, but not the letters*/ @. = @.1 = "---------- Ice and Fire ------------" @.2 = ' ' @.3 = "fire, in end will world the say Some" @.4 = "ice. in say Some" @.5 = "desire of tasted I've what From" @.6 = "fire. favor who those with hold I" @.7 = ' ' @.8 = "... elided paragraph last ..." @.9 = ' ' @.10 = "Frost Robert -----------------------" 

 do   j=1  while  @.j\==;  $=       /*process each "line"; nullify $.*/
   do k=1  for  words(@.j)            /*process each word in the string*/
   $=word(@.j,k) $                    /*prepend the word to a new line.*/
   end   /*k*/                        /* [↑]  could do this another way*/
 say $                                /*display newly constructed line.*/
 end     /*j*/                        /*stick a fork in it, we're done.*/</lang>

output when using the ten lines of input: 

------------ Fire and Ice ----------

Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.

... last paragraph elided ...

----------------------- Robert Frost

Tcl

<lang tcl>set lines { 

   "---------- Ice and Fire ------------"
   ""
   "fire, in end will world the say Some"
   "ice. in say Some"
   "desire of tasted I've what From"
   "fire. favor who those with hold I"
   ""
   "... elided paragraph last ..."
   ""
   "Frost Robert -----------------------"

} foreach line $lines { 

   puts [join [lreverse [regexp -all -inline {\S+} $line]]]
   # This would also work for data this simple:
   ### puts [lreverse $line]

}</lang>

Output:
------------ Fire and Ice ----------

Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favor fire.

... last paragraph elided ...

----------------------- Robert Frost
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