Whilst working my way through "The ANSI C Programming Language" I came across an exercise on chapter one that I just don't understand. The exercise is:
Write a program detab that replaces tabs in the input with the proper
number of blanks to space to the next tab stop. Assume a fixed set of tab stops, say every
n columns. Should n be a variable or a symbolic parameter?
Could someone please explain to me what this is asking? Thank you
Well you could do all your testing with
Then later on, perhaps enhance the code to beCode:int main ( ) { int tabStops = 8; // your code return 0; }
Code:int main ( int argc, char *argv[] ) { int tabStops = 8; // checking for command line params if ( strcmp(argv[i], "--tabs") == 0 ) { tabStops = // parse argv[i+1] } // your code return 0; }
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
There are two questions:
1. You need to write a program that replaces tab characters in the input file with some number of spaces, so that the next character appears at a multiple of n (i.e., a fixed set of tab stops every n columns).
2. Should this n above be a variable of a symbolic constant (i.e., something that is read in from the user or something that is #defined in the code)?
There is something rather freaky about member 'tabstop' answering questions about ... tab stops
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
Yeah, still a little confused...1. You need to write a program that replaces tab characters in the input file with some number of spaces, so that the next character appears at a multiple of n (i.e., a fixed set of tab stops every n columns).
A little bit of research explained tab stops to me, but I don't understand what I'm supposed to do when a \t character is found. Replace it with n spaces, depending on where the tab stops that I defined are? So I'm redefining where all the tab stops in the document are?
Not at all. The file should look the same, visually. But instead ofOriginally Posted by ASCII
(where the arrow represents a single tab character) you should now haveCode:→ Text starts here
(where each symbol represents a space).Code:∙∙∙∙∙∙∙∙Text starts here
...
I'm just replacing each tab with the appropriate number of spaces...
Right. Notice that that is not always n; if the tab had been after the word "Text" for instance, then you would only have done four spaces instead of eight (in this example), since the tabstop is still at column 8.
Yay it work:
Code:#include<stdio.h> #define MAXLENGTH 1000 #define TAB 8 int Getline(char str[]); int main(void) { char line[MAXLENGTH]; int len; while((len = Getline(line)) != 0) printf("%s\n", line); return 0; } int Getline(char str[]) { int i; int c; for(i = 0; i < MAXLENGTH; i++) str[i] = '\0'; for(i = 0; ((c = getchar()) != '\n') && (i < MAXLENGTH); i++) { if(c == EOF) return 0; if(c == '\t'){ int y; for(y = i; y%TAB; y++) str[y] = ' '; i = y; } str[i] = c; } str[i] = '\0'; return i; }
Last edited by ASCII; 08-28-2011 at 04:48 PM.
Now, on to the plural verb forms - Yah!Yay it work:
