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:

 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;
 You are not to explicitly save characters in a collection data structure, such as arrays, strings, hash tables, etc, for later reversal;
 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.


Private Function OddWordFirst(W As String) As String
Dim i As Integer, count As Integer, l As Integer, flag As Boolean, temp As String
   count = 1
   Do
      flag = Not flag
      l = FindNextPunct(i, W) - count + 1
      If flag Then
         temp = temp & ExtractWord(W, count, l)
      Else
         temp = temp & ReverseWord(W, count, l)
      End If
   Loop While count < Len(W)
   OddWordFirst = temp
End Function
 
Private Function FindNextPunct(d As Integer, W As String) As Integer
Const PUNCT As String = ",;:."
   Do
      d = d + 1
   Loop While InStr(PUNCT, Mid(W, d, 1)) = 0
   FindNextPunct = d
End Function
 
Private Function ExtractWord(W As String, c As Integer, i As Integer) As String
   ExtractWord = Mid(W, c, i)
   c = c + Len(ExtractWord)
End Function
 
Private Function ReverseWord(W As String, c As Integer, i As Integer) As String
Dim temp As String, sep As String
   temp = Left(Mid(W, c, i), Len(Mid(W, c, i)) - 1)
   sep = Right(Mid(W, c, i), 1)
   ReverseWord = StrReverse(temp) & sep
   c = c + Len(ReverseWord)
End Function