Odd word problem

From Rosetta Code
Task
Odd word problem
You are encouraged to solve this task according to the task description, using any language you may know.
Task

Write a program that solves the odd word problem with the restrictions given below.


Description

You are promised an input stream consisting of English letters and punctuations.

It is guaranteed that:

  • the words (sequence of consecutive letters) are delimited by one and only one punctuation,
  • the stream will begin with a word,
  • the words will be at least one letter long,   and
  • a full stop (a period, [.]) appears after, and only after, the last word.


Example

A stream with six words:

what,is,the;meaning,of:life.


The task is to reverse the letters in every other word while leaving punctuations intact, producing:

what,si,the;gninaem,of:efil.

while observing the following restrictions:

  1. Only I/O allowed is reading or writing one character at a time, which means: no reading in a string, no peeking ahead, no pushing characters back into the stream, and no storing characters in a global variable for later use;
  2. You are not to explicitly save characters in a collection data structure, such as arrays, strings, hash tables, etc, for later reversal;
  3. You are allowed to use recursions, closures, continuations, threads, co-routines, etc., even if their use implies the storage of multiple characters.


Test cases

Work on both the   "life"   example given above, and also the text:

we,are;not,in,kansas;any,more.



Ada[edit]

This is a rather straightforward approach, using recursion.

with Ada.Text_IO;
 
procedure Odd_Word_Problem is
 
use Ada.Text_IO; -- Get, Put, and Look_Ahead
 
function Current return Character is
-- reads the current input character, without consuming it
End_Of_Line: Boolean;
C: Character;
begin
Look_Ahead(C, End_Of_Line);
if End_Of_Line then
raise Constraint_Error with "end of line before the terminating '.'";
end if;
return C;
end Current;
 
procedure Skip is
-- consumes the current input character
C: Character;
begin
Get(C);
end Skip;
 
function Is_Alpha(Ch: Character) return Boolean is
begin
return (Ch in 'a' .. 'z') or (Ch in 'A' .. 'Z');
end Is_Alpha;
 
procedure Odd_Word(C: Character) is
begin
if Is_Alpha(C) then
Skip;
Odd_Word(Current);
Put(C);
end if;
end Odd_Word;
 
begin -- Odd_Word_Problem
Put(Current);
while Is_Alpha(Current) loop -- read an even word
Skip;
Put(Current);
end loop;
if Current /= '.' then -- read an odd word
Skip;
Odd_Word(Current);
Put(Current);
if Current /= '.' then -- read the remaining words
Skip;
Odd_Word_Problem;
end if;
end if;
end Odd_Word_Problem;

Output:

> ./odd_word_problem 
what,is,the;meaning,of:life.
what,si,the;gninaem,of:efil.
> ./odd_word_problem 
we,are;not,in,kansas;any,more.
we,era;not,ni,kansas;yna,more.

ALGOL 68[edit]

Works with: ALGOL 68G version Any - tested with release 2.8.win32

The words and punctuation should be on a single line. Uses recursion.

# recursively reverses the current word in the input and returns the    #
# the character that followed it #
# "ch" should contain the first letter of the word on entry and will be #
# updated to the punctuation following the word on exit #
PROC reverse word = ( REF CHAR ch )VOID:
BEGIN
 
CHAR next ch;
 
read( ( next ch ) );
 
IF ( next ch <= "Z" AND next ch >= "A" )
OR ( next ch <= "z" AND next ch >= "a" )
THEN
reverse word( next ch )
FI;
 
print( ( ch ) );
 
ch := next ch
 
END; # reverse word #
 
 
 
# recursively prints the current word in the input and returns the #
# character that followed it #
# "ch" should contain the first letter of the word on entry and will be #
# updated to the punctuation following the word on exit #
PROC normal word = ( REF CHAR ch )VOID:
BEGIN
 
print( ( ch ) );
read ( ( ch ) );
 
IF ( ch <= "Z" AND ch >= "A" )
OR ( ch <= "z" AND ch >= "a" )
THEN
normal word( ch )
FI
 
END; # normal word #
 
 
 
# read and print words and punctuation from the input stream, reversing #
# every second word #
PROC reverse every other word = VOID:
BEGIN
 
CHAR ch;
 
read( ( ch ) );
 
WHILE
ch /= "."
DO
normal word( ch );
IF ch /= "."
THEN
print( ( ch ) );
read ( ( ch ) );
reverse word( ch )
FI
OD;
 
print( ( ch ) )
 
END; # reverse every other word #
 
 
 
main: (
reverse every other word
)
Output:
what,si,the;gninaem,of:efil.
we,era;not,ni,kansas;yna,more.

AutoHotkey[edit]

str := "what,is,the;meaning,of:life."
loop, parse, str
if (A_LoopField ~= "[[:punct:]]")
res .= A_LoopField, toggle:=!toggle
else
res := toggle ? RegExReplace(res, ".*[[:punct:]]\K", A_LoopField ) : res A_LoopField
MsgBox % res
Outputs:
what,si,the;gninaem,of:efil.

Bracmat[edit]

( ( odd-word
= dothis doother forward backward
. ( forward
= ch
. fil$:?ch
& put$!ch
& ( low$!ch:~<a:~>z&forward$
| !ch:~"."
)
)
& ( backward
= ch
. fil$:?ch
& ( low$!ch:~<a:~>z
& backward$() (put$!ch&) { This reduces to the return value of backwards$()}
| '(.put$($ch)&$ch:~".") { Macro, evaluates to a function with actual ch. }
)
)
& fil$(!arg,r)
& ((=forward$).(=(backward$)$))
 : (?dothis.?doother)
& whl
' ( !(dothis.)
& (!doother.!dothis):(?dothis.?doother)
)
& (fil$(,SET,-1)|) { This is how a file is closed: seek the impossible. }
)
& put$("what,is,the;meaning,of:life.","life.txt",NEW)
& put$("we,are;not,in,kansas;any,more.","kansas.txt",NEW)
& odd-word$"life.txt"
& put$\n
& odd-word$"kansas.txt" { Real file, as Bracmat cannot read a single character from stdin. }
);

Output:

what,si,the;gninaem,of:efil.
we,era;not,ni,kansas;yna,more.

C[edit]

Using GCC nested function as closures. This can only be passed up the stack, not the other way around. It's also doable with makecontext, and may be possible with setjmp.

#include <stdio.h>
#include <ctype.h>
 
int do_char(int odd, void (*f)(void))
{
int c = getchar();
 
void write_out(void) {
putchar(c);
if (f) f();
}
 
if (!odd) putchar(c);
 
if (isalpha(c))
return do_char(odd, write_out);
 
if (odd) {
if (f) f();
putchar(c);
}
 
return c != '.';
}
 
int main()
{
int i = 1;
while (do_char(i = !i, 0));
 
return 0;
}

C++[edit]

Translation of: Python
Works with: C++11
Works with: gcc version 4.5

Tested with gcc 4.5, with "-std=c++0x" option.

#include <iostream>
#include <cctype>
#include <functional>
 
using namespace std;
 
bool odd()
{
function<void ()> prev = []{};
while(true) {
int c = cin.get();
if (!isalpha(c)) {
prev();
cout.put(c);
return c != '.';
}
prev = [=] { cout.put(c); prev(); };
}
}
 
bool even()
{
while(true) {
int c;
cout.put(c = cin.get());
if (!isalpha(c)) return c != '.';
}
}
 
 
int main()
{
bool e = false;
while( e ? odd() : even() ) e = !e;
return 0;
}

Clojure[edit]

Translation of: Common Lisp
(defn next-char []
(char (.read *in*)))
 
(defn forward []
(let [ch (next-char)]
(print ch)
(if (Character/isLetter ch)
(forward)
(not= ch \.))))
 
(defn backward []
(let [ch (next-char)]
(if (Character/isLetter ch)
(let [result (backward)]
(print ch)
result)
(fn [] (print ch) (not= ch \.)))) )
 
(defn odd-word [s]
(with-in-str s
(loop [forward? true]
(when (if forward?
(forward)
((backward)))
(recur (not forward?)))) )
(println))

Examples:

user=> (odd-word "what,is,the;meaning,of:life.")
what,si,the;gninaem,of:efil.
nil
user=> (odd-word "we,are;not,in,kansas;any,more.")
we,era;not,ni,kansas;yna,more.
nil

CoffeeScript[edit]

isWordChar = (c) -> /^\w/.test c
isLastChar = (c) -> c is '.'
 
# Pass a function that returns an input character and one that outputs a
# character. JS platforms' ideas of single-character I/O vary widely, but this
# abstraction is adaptable to most or all.
oddWord = (get, put) ->
forwardWord = ->
loop
# No magic here; buffer then immediately output.
c = get()
put(c)
unless isWordChar(c)
return not isLastChar(c)
 
# NB: (->) is a CoffeeScript idiom for no-op.
reverseWord = (outputPending = (->)) ->
c = get()
if isWordChar(c)
# Continue word.
# Tell recursive call to output this character, then any previously
# pending characters, after the next word character, if any, has
# been output.
reverseWord ->
put(c)
outputPending()
else
# Word is done.
# Output previously pending characters, then this punctuation.
outputPending()
put(c)
return not isLastChar(c)
 
# Alternate between forward and reverse until one or the other reports that
# the end-of-input mark has been reached (causing a return of false).
continue while forwardWord() and reverseWord()

Same without comments[edit]

isWordChar = (c) -> /^\w/.test c
isLastChar = (c) -> c is '.'
 
oddWord = (get, put) ->
forwardWord = ->
loop
c = get()
put(c)
unless isWordChar(c)
return not isLastChar(c)
 
reverseWord = (outputPending = (->)) ->
c = get()
if isWordChar(c)
reverseWord ->
put(c)
outputPending()
else
outputPending()
put(c)
return not isLastChar(c)
 
continue while forwardWord() and reverseWord()

Testing code[edit]

# Redefine as necessary for target platform.
println = (z) -> console.log z
 
testData = [
[
"what,is,the;meaning,of:life."
"what,si,the;gninaem,of:efil."
]
[
"we,are;not,in,kansas;any,more."
"we,era;not,ni,kansas;yna,more."
]
]
 
results = for [testString, expectedResult] in testData
# This test machinery uses string buffers for input and output. If your JS
# platform sports single-character I/O, by all means, adapt to taste.
getCursor = 0
putBuffer = ""
get = ->
testString.charAt getCursor++
put = (c) ->
putBuffer += c
oddWord(get,put)
[testString, expectedResult, putBuffer, putBuffer is expectedResult]
 
println result for result in results

Output in node.js:

[ 'what,is,the;meaning,of:life.',
  'what,si,the;gninaem,of:efil.',
  'what,si,the;gninaem,of:efil.',
  true ]
[ 'we,are;not,in,kansas;any,more.',
  'we,era;not,ni,kansas;yna,more.',
  'we,era;not,ni,kansas;yna,more.',
  true ]

Common Lisp[edit]

Even words are straightforward. For odd words, the final punctuation is printed by a closure passed back up the caller chain.

(defun odd-word (s)
(let ((stream (make-string-input-stream s)))
(loop for forwardp = t then (not forwardp)
while (if forwardp
(forward stream)
(funcall (backward stream)))) ))
 
(defun forward (stream)
(let ((ch (read-char stream)))
(write-char ch)
(if (alpha-char-p ch)
(forward stream)
(char/= ch #\.))))
 
(defun backward (stream)
(let ((ch (read-char stream)))
(if (alpha-char-p ch)
(prog1 (backward stream) (write-char ch))
#'(lambda () (write-char ch) (char/= ch #\.)))) )
 

Examples:

? (odd-word "what,is,the;meaning,of:life.")
what,si,the;gninaem,of:efil.
NIL
? (odd-word "we,are;not,in,kansas;any,more.")
we,era;not,ni,kansas;yna,more.
NIL

D[edit]

Translation of: C
bool doChar(in bool odd, in void delegate() nothrow f=null) nothrow {
import core.stdc.stdio, std.ascii;
 
immutable int c = getchar;
if (!odd)
c.putchar;
if (c.isAlpha)
return doChar(odd, { c.putchar; if (f) f(); });
if (odd) {
if (f) f();
c.putchar;
}
return c != '.';
}
 
void main() {
bool i = true;
while (doChar(i = !i)) {}
}
Output:
what,is,the;meaning,of:life.
what,si,the;gninaem,of:efil.

EchoLisp[edit]

No character input stream in EchoLisp, which runs in a browser window. We simultate it with a character stream, with the only function read-char, as specified in the task.

 
(lib 'sequences)
(define input-stream null)
(define output-stream "")
 
;;---------------------------
;; character I/O simulation
;; --------------------------
(define (read-char) (next input-stream)) ;; #f if EOF
(define (write-char c) (when c (set! output-stream (string-append output-stream c))))
 
(define (init-streams sentence)
(set! input-stream (procrastinator sentence))
(set! output-stream ""))
 
;;---------------------------------
;; task , using read-char/write-char
;;----------------------------------
 
(define (flop) ; reverses, and returns first non-alpha after word, or EOF
(define c (read-char))
(if (string-alphabetic? c) (begin0 (flop) (write-char c)) c))
 
(define (flip)
(define c (read-char))
(if (string-alphabetic? c) (begin (write-char c) (flip)) c))
 
(define (task sentence)
(init-streams sentence)
(while (and (write-char (flip)) (write-char (flop))))
output-stream )
 
 
 
Output:
 
(task "what,is,the;meaning,of:life.")
"what,si,the;gninaem,of:efil."
; check diacritical
(task "Longtemps,je me suis couché,héhé,hôhô,de bonne heure.")
"Longtemps,ej me sius couché,éhéh,hôhô,ed bonne erueh."
 

Elixir[edit]

Translation of: Erlang
defmodule Odd_word do
def handle(s, false, i, o) when ((s >= "a" and s <= "z") or (s >= "A" and s <= "Z")) do
o.(s)
handle(i.(), false, i, o)
end
def handle(s, t, i, o) when ((s >= "a" and s <= "z") or (s >= "A" and s <= "Z")) do
d = handle(i.(), :rec, i, o)
o.(s)
if t == true, do: handle(d, t, i, o), else: d
end
def handle(s, :rec, _, _), do: s
def handle(?., _, _, o), do: o.(?.); :done
def handle(:eof, _, _, _), do: :done
def handle(s, t, i, o) do
o.(s)
handle(i.(), not t, i, o)
end
 
def main do
i = fn() -> IO.getn("") end
o = fn(s) -> IO.write(s) end
handle(i.(), false, i, o)
end
end
 
Odd_word.main
Output:
C:\Elixir>elixir Odd_word.exs
we,are;not,in,kansas;any,more.
we,era;not,ni,kansas;yna,more.

Erlang[edit]

 
handle(S, false, I, O) when (((S >= $a) and (S =< $z)) or ((S >= $A) and (S =< $Z))) ->
O(S),
handle(I(), false, I, O);
handle(S, T, I, O) when (((S >= $a) and (S =< $z)) or ((S >= $A) and (S =< $Z))) ->
D = handle(I(), rec, I, O),
O(S),
case T of true -> handle(D, T, I, O); _ -> D end;
handle(S, rec, _, _) -> S;
handle($., _, _, O) -> O($.), done;
handle(eof, _, _, _) -> done;
handle(S, T, I, O) -> O(S), handle(I(), not T, I, O).
 
main([]) ->
I = fun() -> hd(io:get_chars([], 1)) end,
O = fun(S) -> io:put_chars([S]) end,
handle(I(), false, I, O).
 

F#[edit]

A recursive solution.

open System
open System.Text.RegularExpressions
 
let mutable Inp = Console.In
 
let Out c = printf "%c" c; (if c = '.' then Environment.Exit 0)
 
let In() = Inp.Read() |> Convert.ToChar
 
let (|WordCharacter|OtherCharacter|) c =
if Regex.IsMatch(c.ToString(),"[a-zA-Z]") then
WordCharacter
else
OtherCharacter
 
let rec forward () =
let c = In()
let rec backward () : char =
let c = In()
match c with
| WordCharacter ->
let s = backward() in Out c; s
| OtherCharacter -> c
Out c
match c with
| WordCharacter -> forward()
| OtherCharacter -> backward()
 
[<EntryPoint>]
let main argv =
if argv.Length > 0 then Inp <- new System.IO.StringReader(argv.[0])
let rec loop () = forward() |> Out; loop()
loop()
0
Output:
>echo we,are;not,in,kansas;any,more. | RosettaCode
we,era;not,ni,kansas;yna,more.
>echo what,is,the;meaning,of:life. | RosettaCode
what,si,the;gninaem,of:efil.

Factor[edit]

This is a delicate program with arcane control flow. To reverse each odd word, this code uses continuations to jump-back into earlier iterations of a while loop. This trick reverses the letters by reversing the loop!

This code is difficult to follow, because it twists its control flow like spaghetti. These continuations form a singly-linked list, where each continuation contains a letter and a previous continuation. The program effectively reverses this linked list.

USING: continuations kernel io io.streams.string locals unicode.categories ;
IN: rosetta.odd-word
 
<PRIVATE
! Save current continuation.
: savecc ( -- continuation/f )
[ ] callcc1 ; inline
 
! Jump back to continuation, where savecc will return f.
: jump-back ( continuation -- )
f swap continue-with ; inline
PRIVATE>
 
:: read-odd-word ( -- )
f :> first-continuation!
f :> last-continuation!
f :> reverse!
 ! Read characters. Loop until end of stream.
[ read1 dup ] [
dup Letter? [
 ! This character is a letter.
reverse [
 ! Odd word: Write letters in reverse order.
last-continuation savecc dup [
last-continuation!
2drop  ! Drop letter and previous continuation.
] [
 ! After jump: print letters in reverse.
drop  ! Drop f.
swap write1  ! Write letter.
jump-back  ! Follow chain of continuations.
] if
] [
 ! Even word: Write letters immediately.
write1
] if
] [
 ! This character is punctuation.
reverse [
 ! End odd word. Fix trampoline, follow chain of continuations
 ! (to print letters in reverse), then bounce off trampoline.
savecc dup [
first-continuation!
last-continuation jump-back
] [ drop ] if
write1  ! Write punctuation.
f reverse!  ! Begin even word.
] [
write1  ! Write punctuation.
t reverse!  ! Begin odd word.
 ! Create trampoline to bounce to (future) first-continuation.
savecc dup [
last-continuation!
] [ drop first-continuation jump-back ] if
] if
] if
] while
 ! Drop f from read1. Then print a cosmetic newline.
drop nl ;
 
: odd-word ( string -- )
[ read-odd-word ] with-string-reader ;
USE: rosetta.odd-word
( scratchpad ) "what,is,the;meaning,of:life." odd-word
what,si,the;gninaem,of:efil.
( scratchpad ) "we,are;not,in,kansas;any,more." odd-word
we,era;not,ni,kansas;yna,more.

FALSE[edit]

This solution uses recursion to read the backwards words, to output the characters after having done the rest of that word.

[$$$$'.=\',=|\';=|\':=|~[^s;!\,]?]s:              {recursive reading}
[s;!$'.=~[,^f;!]?]r: {reverse words}
[[$$$$'.=\',=|\';=|\':=|~][,^]#$'.=~[,^r;!]?]f: {forward words}
^f;!, {start}

Forth[edit]

: word?  dup [char] . <> over bl <> and ;
: ?quit dup [char] . = if emit quit then ;
: eatbl begin dup bl = while drop key repeat ?quit ;
: even begin word? while emit key repeat ;
: odd word? if key recurse swap emit then ;
: main cr key eatbl begin even eatbl space odd eatbl space again ;

Fortran[edit]

By not allowing the use of arrays of characters to facilitate the reversing of texts, the obvious solution involves recursion with storage via the stack so that its last-on, first-off style will achieve the required goal. But alas, Fortran compilers were typically written for computers that did not employ a stack mechanism so recursion was not expected even after the introduction of Algol in the 1960s, and the failure of recursively-invoked routines to return correctly became accepted. The standard murmur was that "Fortran is not a recursive language" even though the language contains recursive definitions such as for arithmetic expressions. By contrast, the B6700 system did employ a hardware stack, and, without any fuss, recursion just worked.

But with F90, the language definition was augmented by the menacing word RECURSIVE, and so...
      MODULE ELUDOM	!Uses the call stack for auxiliary storage.
INTEGER MSG,INF !I/O unit numbers.
LOGICAL DEFER !To stumble, or not to stumble.
CONTAINS
CHARACTER*1 RECURSIVE FUNCTION GET(IN) !Returns one character, going forwards.
INTEGER IN !The input file.
CHARACTER*1 C !The single character to be read therefrom.
READ (IN,1,ADVANCE="NO",EOR=3,END=4) C !Thus. Not advancing to the next record.
1 FORMAT (A1,$) !For output, no advance to the next line either.
2 IF (("A"<=C .AND. C<="Z").OR.("a"<=C .AND. C<="z")) THEN !Unsafe for EBCDIC.
IF (DEFER) THEN !Are we to reverse the current text?
GET = GET(IN) !Yes. Go for the next letter.
WRITE (MSG,1) C !And now, backing out, reveal the letter at this level.
RETURN !Retreat another level.
END IF !Thus passing back the ending non-letter that was encountered.
ELSE !And if we've encountered a non-letter,
DEFER = .NOT. DEFER !Then our backwardness flips.
END IF !Enough inspection of C.
3 GET = C !Pass it back.
RETURN !And we're done.
4 GET = CHAR(0) !Reserving this for end-of-file.
END FUNCTION GET!That was strange.
END MODULE ELUDOM !But as per the specification.
 
PROGRAM CONFUSED !Just so.
USE ELUDOM !Forwards? Backwards?
CHARACTER*1 C !A scratchpad for multiple inspections.
MSG = 6 !Standard output.
INF = 10 !This will do.
OPEN (INF,NAME = "Confused.txt",STATUS="OLD",ACTION="READ") !Go for the file.
 
Chew through the input. A full stop marks the end.
10 DEFER = .FALSE. !Start off going forwards.
11 C = GET(INF) !Get some character from file INF.
IF (ICHAR(C).LE.0) STOP !Perhaps end-of-file is reported.
IF (C.NE." ") WRITE (MSG,12) C !Otherwise, write it. A blank for end-of-record.
12 FORMAT (A1,$) !Obviously, not finishing the line each time.
IF (C.NE.".") GO TO 11 !And if not a full stop, do it again.
WRITE (MSG,"('')") !End the line of output.
GO TO 10 !And have another go.
END !That was confusing.

With file Confused.txt containing the obvious input, the output is

what,si,the;gninaem,of:efil.
we,era;not,ni,kansas;yna,more.
hot,star.

The basic ploy is that the function returns the next character from the input, but, should DEFER be true, it secretly invokes itself until a non-letter is found then returns (bearing that non-letter as its result) and on the way back out, secretly writes the letter previously read. Each level of recursion has its own version of that letter and by revealing them as the returns proceed, they are written in reverse order of input. Seen from the outside of GET, the value of DEFER is always true but this variable is static with regard to the invocations of GET, it being defined outside GET. If it were defined within there would be a new instance allocated with each level of recursion (as with variable C), which is not what is wanted.

Testing showed that the F90 feature of ADVANCE="NO" was required for the READ action because the $ format code that works for output does not work for input. Should an end-of-record interfere with the READ, the EOR=label is taken, and the character read will be a space. To avoid ugly system messages on running into end-of-file, character zero is reserved, just as a space is reserved for end-of-record encounters and skipped for output. Fortunately, the specification does not include spaces as allowed input. No checks are made as to whether the input conforms to the given specifications.

If the ADVANCE feature is unavailable, then the file could be read as UNFORMATTED, one character at a go with a record length of one. And then would arise the annoyance of dealing with the ASCII world's usage of CR, CRLF, LFCR, or CR as markers for the ends of records.

Go[edit]

package main
 
import (
"bytes"
"fmt"
"io"
"os"
"unicode"
)
 
func main() {
owp(os.Stdout, bytes.NewBufferString("what,is,the;meaning,of:life."))
fmt.Println()
owp(os.Stdout, bytes.NewBufferString("we,are;not,in,kansas;any,more."))
fmt.Println()
}
 
func owp(dst io.Writer, src io.Reader) {
byte_in := func () byte {
bs := make([]byte, 1)
src.Read(bs)
return bs[0]
}
byte_out := func (b byte) { dst.Write([]byte{b}) }
var odd func() byte
odd = func() byte {
s := byte_in()
if unicode.IsPunct(rune(s)) {
return s
}
b := odd()
byte_out(s)
return b
}
for {
for {
b := byte_in()
byte_out(b)
if b == '.' {
return
}
if unicode.IsPunct(rune(b)) {
break
}
}
b := odd()
byte_out(b)
if b == '.' {
return
}
}
}

Output:

what,si,the;gninaem,of:efil.
we,era;not,ni,kansas;yna,more.

Using defer[edit]

package main
 
import (
"bytes"
"fmt"
"io"
"os"
"unicode"
)
 
func main() {
owp(os.Stdout, bytes.NewBufferString("what,is,the;meaning,of:life."))
fmt.Println()
owp(os.Stdout, bytes.NewBufferString("we,are;not,in,kansas;any,more."))
fmt.Println()
}
 
func owp(dst io.Writer, src io.Reader) {
byte_in := func () byte {
bs := make([]byte, 1)
src.Read(bs)
return bs[0]
}
byte_out := func (b byte) { dst.Write([]byte{b}) }
odd := func() byte {
for {
b := byte_in()
if unicode.IsPunct(int(b)) {
return b
}
defer byte_out(b)
}
panic("impossible")
}
for {
for {
b := byte_in()
byte_out(b)
if b == '.' {
return
}
if unicode.IsPunct(rune(b)) {
break
}
}
b := odd()
byte_out(b)
if b == '.' {
return
}
}
}

Using channels and goroutines[edit]

Translation of: Ruby
Translation of: Tcl
package main
 
import (
"bytes"
"fmt"
"io"
"os"
"unicode"
)
 
func main() {
owp(os.Stdout, bytes.NewBufferString("what,is,the;meaning,of:life."))
fmt.Println()
owp(os.Stdout, bytes.NewBufferString("we,are;not,in,kansas;any,more."))
fmt.Println()
}
 
type Coroutine struct {
out <-chan Coroutine
in chan<- byte
}
 
func owp(dst io.Writer, src io.Reader) {
byte_in := func () (byte, error) {
bs := make([]byte, 1)
_, err := src.Read(bs)
return bs[0], err
}
byte_out := func (b byte) { dst.Write([]byte{b}) }
 
var f, r Coroutine
 
f = func () Coroutine {
out := make(chan Coroutine)
in := make(chan byte)
var fwd func (byte) byte
fwd = func (c byte) (z byte) {
if unicode.IsLetter(rune(c)) {
byte_out(c)
out <- f
z = fwd(<- in)
} else {
z = c
}
return
}
go func () {
for {
x, ok := <- in
if !ok { break }
byte_out(fwd(x))
out <- r
}
} ()
return Coroutine{ out, in }
} ()
r = func () Coroutine {
out := make(chan Coroutine)
in := make(chan byte)
var rev func (byte) byte
rev = func (c byte) (z byte) {
if unicode.IsLetter(rune(c)) {
out <- r
z = rev(<- in)
byte_out(c)
} else {
z = c
}
return
}
go func () {
for {
x, ok := <- in
if !ok { break }
byte_out(rev(x))
out <- f
}
} ()
return Coroutine{ out, in }
} ()
 
for coro := f; ; coro = <- coro.out {
c, err := byte_in()
if err != nil { break }
coro.in <- c
}
close(f.in)
close(r.in)
}

Haskell[edit]

While it seems like this solution would break the task's rules, Haskell is non-strict, therefore this yields the same behavior of reading and printing one character at a time, without excess storage into a "string". To prove it, run the program and manually enter the input string (Windows command prompt does not respect buffering settings, but urxvt on on Linux does).

import System.IO
 
isAlpha :: Char -> Bool
isAlpha = flip elem $ ['a'..'z'] ++ ['A'..'Z']
 
split :: String -> (String, String)
split = break $ not . isAlpha
 
parse :: String -> String
parse [] = []
parse l =
let (a, w) = split l
(b, x) = splitAt 1 w
(c, y) = split x
(d, z) = splitAt 1 y
in a ++ b ++ reverse c ++ d ++ parse z
 
main :: IO ()
main = hSetBuffering stdin NoBuffering >> hSetBuffering stdout NoBuffering >>
getContents >>= putStr . (takeWhile (/= '.')) . parse >> putStrLn "."

If the above is not acceptable, or if Haskell was implicitly strict, then this solution would satisfy the requirements:

isAlpha :: Char -> Bool
isAlpha = flip elem $ ['a'..'z'] ++ ['A'..'Z']
 
parse :: IO ()
parse = do
x <- getChar
putChar x
case () of
_ | x == '.' -> return ()
| isAlpha x -> parse
| otherwise -> do
c <- revParse
putChar c
if c == '.'
then return ()
else parse
 
revParse :: IO Char
revParse = do
x <- getChar
case () of
_ | x == '.' -> return x
| isAlpha x -> do
c <- revParse
putChar x
return c
| otherwise -> return x
 
main :: IO ()
main = hSetBuffering stdin NoBuffering >> hSetBuffering stdout NoBuffering >>
parse >> putStrLn ""

Linux urxvt output:

$ ./OddWord
wwhhaatt,,is,si,tthhee;;meaning,gninaem,ooff::life.efil.
$ echo "what,is,the;meaning,of:life." | ./OddWord
what,si,the;gninaem,of:efil.
$ echo "we,are;not,in,kansas;any,more." | ./OddWord
we,era;not,ni,kansas;yna,more.

Windows command prompt output:

>OddWord.exe
what,is,the;meaning,of:life.
what,si,the;gninaem,of:efil.
>echo what,is,the;meaning,of:life. | OddWord.exe

what,si,the;gninaem,of;efil.
>echo we,are;not,in,kansas;any,more. | OddWord.exe

we,era;not,ni,kansas;yna,more.

Icon and Unicon[edit]

The following recursive version is based on the non-deferred GO version. A co-expression is used to turn the parameter to the wrapper into a character at a time stream.

procedure main()
every OddWord(!["what,is,the;meaning,of:life.",
"we,are;not,in,kansas;any,more."])
end
 
procedure OddWord(stream) #: wrapper for demonstration
write("Input stream: ",stream)
writes("Output stream: ") & eWord(create !stream,'.,;:') & write()
end
 
procedure eWord(stream,marks) #: handle even words
repeat {
repeat
writes(@stream) ? if ="." then return else if any(marks) then break
if writes(oWord(stream,marks)) == '.' then return
}
end
 
procedure oWord(stream,marks) #: handle odd words (reverse)
if any(marks,s := @stream) then return s
return 1(oWord(stream,marks), writes(s))
end
Output:
Input stream: what,is,the;meaning,of:life.
Output stream: what,si,the;gninaem,of:efil.
Input stream: we,are;not,in,kansas;any,more.
Output stream: we,era;not,ni,kansas;yna,more.

A slightly different solution which uses real I/O from stdin is:

procedure main(A)
repeat (while writes((any(&letters, c := reads(&input,1)),c))) |
(writes(c) ~== "." ~== writes(rWord())) | break write()
end
 
procedure rWord(c)
c1 := rWord((any(&letters, c1 := reads(&input,1)),c1))
writes(\c)
return c1
end

And some sample runs:

->rw
what,is,the;meaning,of:life.
what,si,the;gninaem,of:efil.
->rw
we,are;not,in,kansas;any,more.
we,era;not,ni,kansas;yna,more.
->

J[edit]

This task's requirement to perform buffering implicitly rather than explicitly was perplexing from a J point of view (see talk page for some of that discussion). To avoid this issue, this implementation uses a coroutine-like utility.

J also lacks character stream support, so this implementation uses a stream-like implementation.

putch=: 4 :0                 NB. coroutine verb
outch y
return x
)
 
isletter=: toupper ~: tolower
 
do_char=: 3 :0 NB. coroutine verb
ch=. getch''
if. isletter ch do.
if. odd do.
putch&ch yield do_char '' return.
end.
else.
odd=: -. odd
end.
return ch
)
 
evenodd=: 3 :0
clear_outstream begin_instream y
odd=: 0
whilst. '.'~:char do.
outch char=. do_char coroutine ''
end.
)

Note that in the couroutine-like support page we defined u yield v y such that it produces a result which, when returned to the coroutine helper verb, will cause the deferred execute u v y in a context where both u and v are expected to be coroutine verbs (they will produce a result either wrapped with yield or with return). Likewise return wraps the result with instructions for the coroutine helper, instructing it to use the returned result "as-is". (And, if return is used with an empty stack in the helper, that instance would be the result of the coroutine helper.)

Note that when we curry putch with ch (in putch&ch) we get a verb which needs only one argument. So in this case, x in putch (its left argument) will be the right argument of the derived verb. In other words, in this example, it will be the result of the do_char instance that uses return ch -- this will be the first non-letter character that is seen when dealing with the odd case.

With this implementation:

   evenodd 'what,is,the;meaning,of:life.'
what,si,the;gninaem,of:efil.
evenodd 'we,are;not,in,kansas;any,more.'
we,era;not,ni,kansas;yna,more.

That said, note that this implementation has significant overhead when compared to a more direct implementation of the algorithm.

Java[edit]

public class OddWord {
interface CharHandler {
CharHandler handle(char c) throws Exception;
}
final CharHandler fwd = new CharHandler() {
public CharHandler handle(char c) {
System.out.print(c);
return (Character.isLetter(c) ? fwd : rev);
}
};
class Reverser extends Thread implements CharHandler {
Reverser() {
setDaemon(true);
start();
}
private Character ch; // For inter-thread comms
private char recur() throws Exception {
notify();
while (ch == null) wait();
char c = ch, ret = c;
ch = null;
if (Character.isLetter(c)) {
ret = recur();
System.out.print(c);
}
return ret;
}
public synchronized void run() {
try {
while (true) {
System.out.print(recur());
notify();
}
} catch (Exception e) {}
}
public synchronized CharHandler handle(char c) throws Exception {
while (ch != null) wait();
ch = c;
notify();
while (ch != null) wait();
return (Character.isLetter(c) ? rev : fwd);
}
}
final CharHandler rev = new Reverser();
 
public void loop() throws Exception {
CharHandler handler = fwd;
int c;
while ((c = System.in.read()) >= 0) {
handler = handler.handle((char) c);
}
}
 
public static void main(String[] args) throws Exception {
new OddWord().loop();
}
}

Output is equivalent to that of the Python solution.

Lasso[edit]

define odd_word_processor(str::string) => {
local(
isodd = false,
pos = 1,
invpos = 1,
lastpos = 1
)
while(#str->get(#pos) != '.' && #pos <= #str->size) => {
if(not #str->isAlpha(#pos)) => {
not #isodd ? #isodd = true | #isodd = false
}
if(#isodd) => {
#lastpos = 1
#invpos = 1
while(#str->isAlpha(#pos+#lastpos) && #pos+#lastpos <= #str->size) => {
#lastpos++
}
'odd lastpos: '+#lastpos+'\r'
local(maxpos = #pos+#lastpos-1)
while(#invpos < (#lastpos+1)/2) => {
local(i,o,ipos,opos)
#ipos = #pos+#invpos
#opos = #pos+(#lastpos-#invpos)
#i = #str->get(#ipos)
#o = #str->get(#opos)
 
//'switching '+#i+' and '+#o+'\r'
 
//'insert '+#o+' at '+(#ipos)+'\r'
#str = string_insert(#str,-position=(#ipos),-text=#o)
 
//'remove redundant pos '+(#ipos+1)+'\r'
#str->remove(#ipos+1,1)
 
//'insert '+#i+' at '+(#opos)+'\r'
#str = string_insert(#str,-position=(#opos),-text=#i)
 
//'remove redundant pos '+(#opos+1)+'\r'
#str->remove(#opos+1,1)
 
#invpos++
}
#pos += #lastpos - 1
}
//#str->get(#pos) + #isodd + '\r'
#pos += 1
}
return #str
}
 
'orig:\rwhat,is,the;meaning,of:life.\r'
'new:\r'
odd_word_processor('what,is,the;meaning,of:life.')
'\rShould have:\rwhat,si,the;gninaem,of:efil.'
Output:
orig:
what,is,the;meaning,of:life.
new:
what,si,the;gninaem,of:efil.
Should have:
what,si,the;gninaem,of:efil.

Nim[edit]

Translation of: Python
import os, unicode, future
 
proc nothing(): bool{.closure.} = false
 
proc odd(prev = nothing): bool =
let a = stdin.readChar()
if not isAlpha(Rune(ord(a))):
discard prev()
stdout.write(a)
return a != '.'
 
# delay action until later, in the shape of a closure
proc clos(): bool =
stdout.write(a)
prev()
 
return odd(clos)
 
proc even(): bool =
while true:
let c = stdin.readChar()
stdout.write(c)
if not isAlpha(Rune(ord(c))):
return c != '.'
 
var e = false
while (if e: odd() else: even()):
e = not e

Output:

$ echo "what,is,the;meaning,of:life." | ./oddword
what,si,the;gninaem,of:efil.
echo "we,are;not,in,kansas;any,more." | ./oddword
we,era;not,ni,kansas;yna,more.

OCaml[edit]

let is_alpha c =
c >= 'a' && c <= 'z' ||
c >= 'A' && c <= 'Z'
 
let rec odd () =
let c = input_char stdin in
if is_alpha c
then (let e = odd () in print_char c; e)
else (c)
 
let rec even () =
let c = input_char stdin in
if is_alpha c
then (print_char c; even ())
else print_char c
 
let rev_odd_words () =
while true do
even ();
print_char (odd ())
done
 
let () =
try rev_odd_words ()
with End_of_file -> ()

Executing:

$ echo "what,is,the;meaning,of:life." | ocaml odd_word_problem.ml
what,si,the;gninaem,of:efil.

Perl[edit]

All versions process text until EOF, not dot.

Input:

what,is,the;meaning,of:life.

Output:

what,si,the;gninaem,of:efil.

Closure version[edit]

sub r
{
my ($f, $c) = @_;
return sub { print $c; $f->(); };
}
 
$r = sub {};
 
while (read STDIN, $_, 1) {
$w = /^[a-zA-Z]$/;
$n++ if ($w && !$l);
$l = $w;
if ($n & 1 || !$w) {
$r->(); $r = sub{};
print;
} else {
$r = r($r, $_);
}
}
$r->();

Recursion version[edit]

sub rev
{
my $c;
read STDIN, $c, 1;
if ($c =~ /^[a-zA-Z]$/) {
my $r = rev();
print $c;
return $r;
} else {
return $c;
}
}
 
while (read STDIN, $_, 1) {
$w = /^[a-zA-Z]$/;
$n++ if ($w && !$l);
$l = $w;
if ($n & 1) {
print;
} else {
my $r = rev();
print $_;
print $r;
$n = 0; $l = 0;
}
}

Threads (processes) version[edit]

Perl still has weak threads support. Far more safe yet portable is to use processes (fork).

Here, fork is used instead of threads and pipe is used instead of conditional variable.

$|=1;
 
while (read STDIN, $_, 1) {
$w = /^[a-zA-Z]$/;
$n++ if ($w && !$l);
$l = $w;
if ($n & 1 || !$w) {
close W; while(wait()!=-1){}
print;
} else {
open W0, ">&", \*W;
close W;
pipe R,W;
if (!fork()) {
close W;
<R>;
print $_;
close W0;
exit;
}
close W0;
close R;
}
}

Perl 6[edit]

A recursive solution, with the added feature that it treats each line separately.

my &in = { $*IN.getc // last }
 
loop {
ew(in);
ow(in).print;
}
 
multi ew ($_ where /\w/) { .print; ew(in); }
multi ew ($_) { .print; next when "\n"; }
 
multi ow ($_ where /\w/) { ow(in) x .print; }
multi ow ($_) { $_; }
Output:
$ ./oddword
we,are;not,in,kansas;any,more.
we,era;not,ni,kansas;yna,more.
what,is,the;meaning,of:life.
what,si,the;gninaem,of:efil.

Note how the even/oddness is reset on the line boundary; if not, the second line might have started out in an odd state and reversed "what" instead of "is". The call to next prevents that by sending the loop back to its initial state.

There is one clever trick here with the x operator; it evaluates both its arguments in order, but in this case only returns the left argument because the right one is always 1 (True). You can think of it as a reversed C-style comma operator.

Phix[edit]

Uses plain and simple recursion, no closures, and no other tricks.
To test direct console input, comment out string s .. getchar(), and uncomment getc(0) and the prompt.
Likewise use integer fn = open("somefile","r"), and getc(fn) should you want to test file i/o.

string s = "what,is,the;meaning,of:life."
--string s = "we,are;not,in,kansas;any,more."
integer i = 0
 
function getchar()
i += 1
return s[i]
end function
 
function wrod(integer rev)
integer ch = getchar(), nch
-- integer ch = getc(0), nch
if not find(ch," .,:;!?") then
if rev then
nch = wrod(rev)
end if
puts(1,ch)
if not rev then
nch = wrod(rev)
end if
ch = nch
end if
return ch
end function
 
--puts(1,"Enter words separated by a single punctuation mark (i.e. !?,.;:) and ending with .\n")
integer rev = 0
while 1 do
integer ch = wrod(rev)
puts(1,ch)
if ch='.' then exit end if
rev = 1-rev
end while
Output:
what,si,the;gninaem,of:efil.
we,era;not,ni,kansas;yna,more.

PHP[edit]

Translation of: Python
$odd = function ($prev) use ( &$odd ) {
$a = fgetc(STDIN);
if (!ctype_alpha($a)) {
$prev();
fwrite(STDOUT, $a);
return $a != '.';
}
$clos = function () use ($a , $prev) {
fwrite(STDOUT, $a);
$prev();
};
return $odd($clos);
};
$even = function () {
while (true) {
$c = fgetc(STDIN);
fwrite(STDOUT, $c);
if (!ctype_alpha($c)) {
return $c != ".";
}
}
};
$prev = function(){};
$e = false;
while ($e ? $odd($prev) : $even()) {
$e = !$e;
}

PicoLisp[edit]

(de oddWords ()
(use C
(loop
(until (sub? (prin (setq C (char))) "!,.:;?"))
(T (= "." C))
(setq C (char))
(T
(= "."
(prin
(recur (C)
(if (sub? C "!,.:;?")
C
(prog1 (recurse (char)) (prin C)) ) ) ) ) ) )
(prinl) ) )

Test:

(in "txt1" (oddWords))
(in "txt2" (oddWords))

Output:

what,si,the;gninaem,of:efil.
we,era;not,ni,kansas;yna,more.

PL/I[edit]

test: procedure options (main);  /* 2 August 2014 */
declare (ch, ech) character (1);
declare odd file;
 
get_word: procedure recursive;
declare ch character (1);
 
get file (odd) edit (ch) (a(1));
if index('abcdefghijklmnopqrstuvwxyz', ch) > 0 then call get_word;
if index('abcdefghijklmnopqrstuvwxyz', ch) > 0 then
put edit (ch) (a);
else ech = ch;
end get_word;
 
open file (odd) input title ('/ODDWORD.DAT,TYPE(text),recsize(100)');
do forever;
do until (index('abcdefghijklmnopqrstuvwxyz', ch) = 0 );
get file (odd) edit (ch) (a(1)); put edit (ch) (a);
end;
if ch = '.' then leave;
call get_word;
put edit (ech) (a);
if ech = '.' then leave;
end;
end test;

file:

what,is,the;meaning,of:life.

output:

what,si,the;gninaem,of:efil.

file:

we,are;not,in,kansas;any,more.

output:

we,era;not,ni,kansas;yna,more.

Prolog[edit]

Works with SWI-Prolog.

odd_word_problem :-
read_line_to_codes(user_input, L),
even_word(L, Out, []),
string_to_list(Str, Out),
writeln(Str).
 
even_word(".") --> ".".
 
even_word([H | T]) -->
{char_type(H,alnum)},
[H],
even_word(T).
 
even_word([H | T]) -->
[H],
odd_word(T, []).
 
odd_word(".", R) --> R, ".".
 
odd_word([H|T], R) -->
{char_type(H,alnum)},
odd_word(T, [H | R]).
 
odd_word([H|T], R) -->
R,
[H],
even_word(T).
 

Output :

?- odd_word_problem.
|: what,is,the;meaning,of:life.
what,si,the;gninaem,of:efil.
true .

?- odd_word_problem.
|: we,are;not,in,kansas;any,more.
we,era;not,ni,kansas;yna,more.
true .

PureBasic[edit]

This example uses recursion.

#False = 0
#True = 1
 
Global *inputPtr.Character
 
Macro nextChar()
*inputPtr + SizeOf(Character)
EndMacro
 
Procedure isPunctuation(c.s)
If FindString("!?()[]{},.;:-'" + #DQUOTE$, c)
ProcedureReturn #True
EndIf
ProcedureReturn #False
EndProcedure
 
Procedure oddWord()
Protected c.c
c = *inputPtr\c
If isPunctuation(Chr(*inputPtr\c))
ProcedureReturn
Else
nextChar()
oddWord()
EndIf
Print(Chr(c))
EndProcedure
 
Procedure oddWordProblem(inputStream.s)
*inputPtr = @inputStream
Define isOdd = #False
While *inputPtr\c
If isOdd
oddWord()
Else
Repeat
Print(Chr(*inputPtr\c))
nextChar()
Until isPunctuation(Chr(*inputPtr\c))
EndIf
Print(Chr(*inputPtr\c))
isOdd ! 1 ;toggle word indicator
nextChar()
Wend
EndProcedure
 
Define inputStream.s
If OpenConsole()
Repeat
PrintN(#CRLF$ + #CRLF$ + "Enter a series of words consisting only of English letters (i.e. a-z, A-Z)")
PrintN("and that are separated by a punctuation mark (i.e. !?()[]{},.;:-' or " + #DQUOTE$ + ").")
inputStream = Input()
oddWordProblem(inputStream) ;assume input is correct
Until inputStream = ""
 
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf

Sample output:

Enter a series of words consisting only of English letters (i.e. a-z, A-Z)
and that are separated by a punctuation mark (i.e. !?()[]{},.;:-' or ").
what,is,the;meaning,of:life.
what,si,the;gninaem,of:efil.

Enter a series of words consisting only of English letters (i.e. a-z, A-Z)
and that are separated by a punctuation mark (i.e. !?()[]{},.;:-' or ").
we,are;not,in,kansas;any,more.
we,era;not,ni,kansas;yna,more.

Python[edit]

from sys import stdin, stdout
 
def char_in(): return stdin.read(1)
def char_out(c): stdout.write(c)
 
def odd(prev = lambda: None):
a = char_in()
if not a.isalpha():
prev()
char_out(a)
return a != '.'
 
# delay action until later, in the shape of a closure
def clos():
char_out(a)
prev()
 
return odd(clos)
 
def even():
while True:
c = char_in()
char_out(c)
if not c.isalpha(): return c != '.'
 
e = False
while odd() if e else even():
e = not e
Running:
$ echo "what,is,the;meaning,of:life." | python odd.py
what,si,the;gninaem,of:efil.
$ echo "we,are;not,in,kansas;any,more." | python odd.py
we,era;not,ni,kansas;yna,more.
Translation of: Scheme

In this version, the action of printing the terminating punctuation is put in a closure and returned by odd().

from sys import stdin, stdout
 
def char_in(): return stdin.read(1)
def char_out(c): stdout.write(c)
 
def odd():
a = char_in()
if a.isalpha():
r = odd()
char_out(a)
return r
 
# delay printing terminator until later, in the shape of a closure
def clos():
char_out(a)
return a != '.'
 
return clos
 
def even():
while True:
c = char_in()
char_out(c)
if not c.isalpha(): return c != '.'
 
e = False
while odd()() if e else even():
e = not e

Using coroutines and recursion[edit]

Translation of: Ruby
Translation of: Tcl
Works with: Python version 3.3+
from sys import stdin, stdout
 
def fwd(c):
if c.isalpha():
return [stdout.write(c), (yield from fwd((yield f)))][1]
else:
return c
 
def rev(c):
if c.isalpha():
return [(yield from rev((yield r))), stdout.write(c)][0]
else:
return c
 
def fw():
while True:
stdout.write((yield from fwd((yield r))))
 
def re():
while True:
stdout.write((yield from rev((yield f))))
 
f = fw()
r = re()
next(f)
next(r)
 
coro = f
while True:
c = stdin.read(1)
if not c:
break
coro = coro.send(c)

Racket[edit]

Simple solution, using a continuation thunk for the reverse parts.

 
#!/bin/sh
#|
exec racket -tm- "$0" "$@"
|#
 
#lang racket
 
(define (even k)
(define c (read-char))
(cond [(eq? c eof) (k)]
[(not (char-alphabetic? c)) (k) (write-char c) (odd)]
[else (even (λ() (write-char c) (k)))]))
 
(define (odd)
(define c (read-char))
(unless (eq? c eof)
(write-char c)
(if (char-alphabetic? c) (odd) (even void))))
 
(provide main)
(define (main) (odd) (newline))
 
;; (with-input-from-string "what,is,the;meaning,of:life." main)
;; ;; -> what,si,the;gninaem,of:efil.
;; (with-input-from-string "we,are;not,in,kansas;any,more." main)
;; ;; -> we,era;not,ni,kansas;yna,more.
 

REXX[edit]

The REXX program writes some header information to aid in visual fidelity when displaying the output to the
screen (also a blank line is written to make the screen display righteous;   it's assumed that writing titles and
blank lines doesn't break the spirit of the restrictions (single character I/O)   [the 8th line with the three says].
This displaying of informative messages is only to help the observer to know what is being performed.

No recursion or the stack is used.   The program could've been written without subroutines.

/*REXX program  solves the  odd word  problem  by  only using  byte  input/output.      */
iFID_ = 'ODDWORD.IN' /*Note: numeric suffix is added later.*/
oFID_ = 'ODDWORD.' /* " " " " " " */
 
do case=1 for 2; #=0 /*#: is the number of characters read.*/
iFID=iFID_ || case /*read ODDWORD.IN1 or ODDWORD.IN2 */
oFID=oFID_ || case /*write ODDWORD.1 o r ODDWORD.2 */
say; say; say '════════ reading file: ' iFID "════════" /* ◄■■■■■■■■■ optional. */
 
do until x==. /* [↓] perform for "odd" words.*/
do until \isMix(x); /* [↓] perform until punct found.*/
call readChar; call writeChar /*read and write a letter. */
end /*until ¬isMix(x)*/ /* [↑] keep reading " " */
if x==. then leave /*is this the end─of─sentence ? */
call readLetters; punct=# /*save the location of punctuation*/
do j=#-1 by -1; call readChar j /*read previous word (backwards). */
if \isMix(x) then leave; call writeChar /*Found punctuation? Then leave. */
end /*j*/ /* [↑] perform for "even" words.*/
call readLetters; call writeChar; #=punct /*read/write letters; new location*/
end /*until x==.*/
end /*case*/ /* [↑] process both input files. */
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
isMix: return datatype( arg(1), 'M') /*return 1 if argument is a letter.*/
readLetters: do until \isMix(x); call readChar; end; return
writeChar: call charout , x; call charout oFID, x; return
/*──────────────────────────────────────────────────────────────────────────────────────*/
readChar: if arg(1)=='' then do; x=charin(iFID); #=#+1; end /*read the next char*/
else x=charin(iFID, arg(1)) /* " specific " */
return

output   when using two (default) input files which contain:

  •   input file   ODDWORD.IN1   ───►   what,is,the;meaning,of:life.
  •   input file   ODDWORD.IN2   ───►   we,are;not,in,kansas;any,more.


The output is written to the terminal screen as well as to a couple of unique files.   Only the screen output is
shown here, the output files mirror the display except for the headers   (reading file:   xxx)   and the writing
(SAYing) of blank lines which helps keep the screen righteous after using the REXX   charout   BIF   which
wrote to the terminal.

════════ reading file:  ODDWORD.IN1 ════════
what,si,the;gninaem,of:efil.

════════ reading file:  ODDWORD.IN2 ════════
we,era;not,ni,kansas;yna,more.

Ruby[edit]

These Ruby programs store each character in a single-character string.

Using fibers and recursion[edit]

Translation of: Tcl
Works with: Ruby version 1.9
f, r = nil
fwd = proc {|c|
c =~ /[[:alpha:]]/ ? [(print c), fwd[Fiber.yield f]][1] : c }
rev = proc {|c|
c =~ /[[:alpha:]]/ ? [rev[Fiber.yield r], (print c)][0] : c }
 
(f = Fiber.new { loop { print fwd[Fiber.yield r] }}).resume
(r = Fiber.new { loop { print rev[Fiber.yield f] }}).resume
 
coro = f
until $stdin.eof?
coro = coro.resume($stdin.getc)
end

Using continuations[edit]

Translation of: Factor
Library: continuation
require 'continuation' unless defined? Continuation
require 'stringio'
 
# Save current continuation.
def savecc(*data)
# With MRI 1.8 (but not 1.9), the array literal
# [callcc {|cc| cc}, *data]
# used the wrong return value from callcc. The workaround is to
# put callcc outside the array literal.
continuation = callcc {|cc| cc}
[continuation, *data]
end
 
# Jump back to continuation, where savecc will return [nil, *data].
def jump_back(continuation)
continuation[nil]
end
 
def read_odd_word(input, output)
first_continuation, last_continuation = nil
reverse = false
# Read characters. Loop until end of stream.
while c = input.getc
c = c.chr # For Ruby 1.8, convert Integer to String.
if c =~ /[[:alpha:]]/
# This character is a letter.
if reverse
# Odd word: Write letters in reverse order.
saving, last_continuation, c = savecc(last_continuation, c)
if saving
last_continuation = saving
else
# After jump: print letters in reverse.
output.print c
jump_back last_continuation
end
else
# Even word: Write letters immediately.
output.print c
end
else
# This character is punctuation.
if reverse
# End odd word. Fix trampoline, follow chain of continuations
# (to print letters in reverse), then bounce off trampoline.
first_continuation, c = savecc(c)
if first_continuation
jump_back last_continuation
end
output.print c # Write punctuation.
reverse = false # Begin even word.
else
output.print c # Write punctuation.
reverse = true # Begin odd word.
# Create trampoline to bounce to (future) first_continuation.
last_continuation, = savecc
unless last_continuation
jump_back first_continuation
end
end
end
end
output.puts # Print a cosmetic newline.
end
 
def odd_word(string)
read_odd_word StringIO.new(string), $stdout
end
 
odd_word "what,is,the;meaning,of:life."
odd_word "we,are;not,in,kansas;any,more."

Run BASIC[edit]

open "oddWord.txt" for input as #f               ' read input stream
while not(eof(#f))
line input #f, a$
oddW$ = "" ' begin the result oddW with blank
px = 0 ' begin word search location with 0
count = 0 ' begin the word count to 0
while x < len(a$) ' look at each character
x = instr(a$,",",px) ' search for comma (,)
if x = 0 then x = len(a$) ' no more commas?
x1 = instr(a$,";",px) ' search for (;)
x2 = instr(a$,":",px) ' search for (:)
if x1 <> 0 then x = min(x,x1) ' what came first the , ; or :
if x2 <> 0 then x = min(x,x2)
 
w$ = mid$(a$,px,x - px) ' get the word seperated by , ; or :
 
if count and 1 then ' is it the odd word
w1$ = ""
for i = len(w$) to 1 step -1
w1$ = w1$ + mid$(w$,i,1) ' reverse odd words
next i
w$ = w1$
end if
oddW$ = oddW$ + w$ + mid$(a$,x,1) ' add the word to the end of oddW$
px = x + 1 ' bump word search location for next while
count = count + 1 ' count the words
wend
print a$;" -> ";oddW$ ' print the original and result
next ii
wend
close #f
what,is,the;meaning,of:life.   -> what,si,the;gninaem,of:efil.
we,are;not,in,kansas;any,more. -> we,era;not,ni,kansas;yna,more.

Scala[edit]

import scala.io.Source
import java.io.PrintStream
 
def process(s: Source, p: PrintStream, w: Int = 0): Unit = if (s.hasNext) s.next match {
case '.' => p append '.'
case c if !Character.isAlphabetic(c) => p append c; reverse(s, p, w + 1)
case c => p append c; process(s, p, w)
}
 
def reverse(s: Source, p: PrintStream, w: Int = 0, x: Char = '.'): Char = s.next match {
case c if !Character.isAlphabetic(c) => p append x; c
case c => val n = reverse(s, p, w, c);
if (x == '.') {p append n; process(s, p, w + 1)} else p append x; n
}
 
process(Source.fromString("what,is,the;meaning,of:life."), System.out); println
process(Source.fromString("we,are;not,in,kansas;any,more."), System.out); println
Output:
what,si,the;gninaem,of:efil.
we,era;not,ni,kansas;yna,more.

Scheme[edit]

Output is identical to python.

(define (odd)
(let ((c (read-char)))
(if (char-alphabetic? c)
(let ((r (odd)))
(write-char c)
r)
(lambda () (write-char c) (char=? c #\.)))))
 
(define (even)
(let ((c (read-char)))
(write-char c)
(if (char-alphabetic? c)
(even)
(char=? c #\.))))
 
(let loop ((i #f))
(if (if i ((odd)) (even))
(exit)
(loop (not i))))

Seed7[edit]

$ include "seed7_05.s7i";
include "chartype.s7i";
 
const func char: doChar (in boolean: doReverse) is func
result
var char: delimiter is ' ';
local
var char: ch is ' ';
begin
ch := getc(IN);
if ch in letter_char then
if doReverse then
delimiter := doChar(doReverse);
write(ch);
else
write(ch);
delimiter := doChar(doReverse);
end if;
else
delimiter := ch;
end if;
end func;
 
const proc: main is func
local
var char: delimiter is ' ';
var boolean: doReverse is FALSE;
begin
repeat
delimiter := doChar(doReverse);
write(delimiter);
doReverse := not doReverse;
until delimiter = '.';
writeln;
end func;
Output:
> s7 oddWordProblem
SEED7 INTERPRETER Version 5.0.5203  Copyright (c) 1990-2014 Thomas Mertes
what,is,the;meaning,of:life.
what,si,the;gninaem,of:efil.

Sidef[edit]

Recursive solution:

Translation of: Perl
func rev {
(var c = STDIN.getc) \\ return()
if (c ~~ /^[a-z]\z/i) {
var r = rev()
print c
return r
}
return c
}
 
var (n=0, l=false)
while (defined(var c = STDIN.getc)) {
var w = (c ~~ /^[a-z]\z/i)
++n if (w && !l)
l = w
if (n & 1) {
print c
} else {
var r = rev()
print(c, r)
n = 0
l = false
}
}
Output:
$ echo 'what,is,the;meaning,of:life.' | sidef script.sf
what,si,the;gninaem,of:efil.

$ echo 'we,are;not,in,kansas;any,more.' | sidef script.sf
we,era;not,ni,kansas;yna,more.

Tcl[edit]

Although the input is handled as strings, they're all as single-character strings.

Works with: Tcl version 8.6
package require Tcl 8.6
 
proc fwd c {
expr {[string is alpha $c] ? "[fwd [yield f][puts -nonewline $c]]" : $c}
}
proc rev c {
expr {[string is alpha $c] ? "[rev [yield r]][puts -nonewline $c]" : $c}
}
coroutine f while 1 {puts -nonewline [fwd [yield r]]}
coroutine r while 1 {puts -nonewline [rev [yield f]]}
for {set coro f} {![eof stdin]} {} {
set coro [$coro [read stdin 1]]
}

Output is identical to Python and Scheme versions.

The only difference between the two coroutines (apart from the different names used when flipping back and forth) is the timing of the write of the character with respect to the recursive call.

TUSCRIPT[edit]

This example is incorrect. Please fix the code and remove this message.
Details: You are supposed to read characters one by one and not store them in arrays.
 
$$ MODE TUSCRIPT
inputstring=*
DATA what,is,the;meaning,of:life.
DATA we,are;not,in,kansas;any,more.
 
BUILD C_GROUP >[pu]=".,;:-"
 
LOOP i=inputstring
pu=STRINGS (i,"|>[pu]|")
wo=STRINGS (i,"|<></|")
outputstring=""
loop n,w=wo,p=pu
r=MOD(n,2)
IF (r==0) w=TURN (w)
outputstring=CONCAT(outputstring,w,p)
ENDLOOP
PRINT outputstring
ENDLOOP
 

Output:

what,si,the;gninaem,of:efil.Brian:
we,era;not,ni,kansas;yna,more. 

zkl[edit]

Translation of: D
var [const] delim=",:;/?!@#$%^&*()_+", stop=".";
fcn oddly(inStream){
inStream=inStream.walker(3); // character iterator: string, file, etc
doWord:=fcn(inStream,rev,f){ // print next word forewards or reverse
c:=inStream.next();
if(not rev) c.print();
if(not (c==stop or delim.holds(c)))
return(self.fcn(inStream,rev,'{ c.print(); f(); }));
if(rev){ f(); c.print(); }
return(c!=stop);
};
tf:=Walker.cycle(False,True); // every other word printed backwords
while(doWord(inStream, tf.next(), Void)) {}
println();
}

Showing two different input streams:

oddly("what,is,the;meaning,of:life.");
oddly(Data(0,String,"we,are;not,in,kansas;any,more."));
Output:
what,si,the;gninaem,of:efil.
we,era;not,ni,kansas;yna,more.