C Recursion (explain) Post: 302416390

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Top Forums Programming C Recursion (explain) Post 302416390 by jim mcnamara on Monday 26th of April 2010 10:29:59 AM

04-26-2010

Registered User

Code:

void printit(char line_of_char[], int index)
{
 if(line_of_char[index])
 {
  index++;
  printf("+%c", line_of_char[index]); /*how come this is not being printed after "-" was printed*/
  printit(line_of_char, index);
  printf("-%c", line_of_char[index]);
 }
}

function call pushes data onto the stack, so what this does is to push various
values of index onto the stack. The first print statement is using the value of index as it gets incremented 1,2,3 ...

The second printf (after the recursive call) statement is going "back in time" by popping values off the stack 10,9,8, .....

Change the code so it just prints value of the index variable, nothing else. Then you will see.

BTW the "if(line_of_char[index])" has a problem, the initial value is -1, which is the character before the start of the variable line_of_char. Apparently it works for you, but that it called "programming by coincidence" a really bad thing. It could trigger a segfault on other systems. Or other problems.

---------- Post updated at 08:29 ---------- Previous update was at 08:16 ----------

Corrected code, sort of:

Code:

#include <stdio.h>
#include <string.h>

void printit(char line_of_char[], int index);
int main()
{
   char line_of_char[80]={0x0};
   int index = -1;
   
   strcpy(line_of_char, "This is a string.");
   printit(line_of_char, index);
   printf("\n");
   return 0;
}
void printit(char line_of_char[], int index)
{
   if(index ==-1 || line_of_char[index])
   {   
   	index++;
    printf("+%c", line_of_char[index]); 
    printit(line_of_char, index);
    printf("-%c", line_of_char[index]);
   }
}

Last edited by jim mcnamara; 04-26-2010 at 11:23 AM..

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diction(1)						      General Commands Manual							diction(1)

NAME

       diction, explain, suggest - Prints wordy sentences and looks them up in an interactive thesaurus.

SYNOPSIS

       diction [-fpattern_file] [-k] [-ma] [-me] [-ml] [-ms] [-n] [file...]

       explain

       suggest

       The  diction command finds all sentences in an English language document that contain phrases from a database of bad or wordy diction.  The
       explain command is an interactive thesaurus for the English language phrases found by the diction command and only for those phrases.

       The diction command reads from standard in if no file operand is provided.

       The suggest command is a synonym for explain.

OPTIONS

       Names a user-created pattern file to be used in addition to the default file.  Passes the -k option to the deroff command.  The	-k  option
       keeps  blocks  of  text	specified nroff by requests or macros; for example, the request.  Passes the -ma option to deroff.  The -ma option
       interprets nroff man macros only.  Overrides the default nroff -ms macro package.  Causes deroff to skip lists; should be used if  a  docu-
       ment  contains  many  lists of nonsentences.  Overrides the default nroff -ms macro package.  Suppresses use of the default file (used with
       -f).  Only the user-created pattern file is used.

DESCRIPTION

       Each phrase found by the diction command is enclosed in [ ] (brackets).	Because diction runs deroff before looking at  the  text,  include
       formatting header files as part of the input.

       Before using the explain command, use the diction command to obtain a list of poorly worded phrases.  When you use the explain command, the
       system prompts you for a phrase and responds with a grammatically acceptable alternative.  You can continue typing phrases, or you can exit
       by pressing the End-of-File key sequence.

       The explain command can also take input redirected from a file. No other command line arguments are valid.

NOTES

       Use of nonstandard formatting macros may cause incorrect sentence breaks.  In particular, diction does not understand -me.

FILES

       Default pattern file.  Thesaurus used by the explain command.

SEE ALSO

       Commands:  deroff(1), nroff(1)

																	diction(1)

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