Thread: array problem

Greater than zero is used to determine if the line has valid data on it, or is just a blank line.

Even though these functions are from K&R, remove this:

Code:

!= EOF && c

Or, simply replace the && operator to ||. Beginners should not be using EOF in a console.

Originally Posted by elwad

there code i dont understand 1 line in it i dont understand

Code:

#include <stdio.h>
#define MAXLINE 1000 /* maximum input line length */
int getline(char line[], int maxline);
void copy(char to[], char from[]);
/* print the longest input line */
int main(void)
{
    int len; /* current line length */
    int max; /* maximum length seen so far */
    char line[MAXLINE]; /* current input line */
    char longest[MAXLINE]; /* longest line saved here */
    max = 0;
    while ((len = getline(line, MAXLINE)) > 0)
         if (len > max) {
             max = len;
             copy(longest, line);}
         if (max > 0) /* there was a line */
             printf("%s", longest);
    getchar();
    return 0;
}
/* getline: read a line into s, return length */
int getline(char s[],int lim)
{
    int c, i;
    for (i=0; i < lim-1 && (c=getchar())!=EOF && c!='\n'; ++i)
            s[i] = c;
    if ( c == '\n' ){
        s[i] = c;
        ++i;}
    s[i] = '\0';
    return i;
}
/* copy: copy 'from' into 'to'; assume to is big enough */
void copy(char to[], char from[])
{
     int i;
     i = 0;
     while( (to[i] = from[i]) != '\0')
         ++i;
}

is bigger than zero means when he reached EOF but EOF is -1 right shouldnt that be -1 not 0 ?also the int c in 2nd loop why its using s[i]=c and he didnt in the for loop set it anything to the array s ?

what's actually is ur problem?max is the length of the the line which will always be either greater than or equal to 0(in the case the line doesn't have any character).

I use tests for EOF in lots of my console functions and programs.

You will definitely want to use EOF when you're working with text files.

You might also remember that while K&R are merely mortals and make mistakes, they are also blatantly brilliant with their work in the C language.

I would hesitate so many times before I said someone should change something substantive, in their famous book.

srry electricity was out my problem that i dont understand that getline function i understand some stuff but genrally i dont get its idea and K&R is a really great book i have just started c programming and it taught me alot of stuff.

Originally Posted by elwad

srry electricity was out my problem that i dont understand that getline function i understand some stuff but genrally i dont get its idea and K&R is a really great book i have just started c programming and it taught me alot of stuff.

the getline() function takes a line with as much as 999 characters in it and the condition is that as oon as u press EOF the line will be finished and also if '\n' is pressed the line will be changed and the last character of the lin ewill be '\n'.

Originally Posted by BEN10

the getline() function takes a line with as much as 999 characters in it and the condition is that as oon as u press EOF the line will be finished and also if '\n' is pressed the line will be changed and the last character of the lin ewill be '\n'.

so in getline function s[i] = c it cr8tes the string but this check

Code:

 if 
(
c == '\n') {s[i] = c;
++i;

} why did he do this coz a string doesnt contain \n ?also in main

Code:

while ((len = getline(line, MAXLINE)) > 0)

i thought EOF is -1 not bigger than zero ?

len refers to the length of the string, not whether the file pointer has reached the EOF.

He wants to include the newline char, and (I believe), count it as another line of text. (++i).

Originally Posted by elwad

so in getline function s[i] = c it cr8tes the string but this check

Code:

 if 
(
c == '\n') {s[i] = c;
++i;

} why did he do this coz a string doesnt contain \n ?also in main

Code:

while ((len = getline(line, MAXLINE)) > 0)

i thought EOF is -1 not bigger than zero ?

if u press "ENTER" the line will be changed so the last character pressed is '\n' so the loop breaks and the last character pressed is '\n' which is give by if(c=='\n').
also len is the length of the the characters inputted by the user which will always be >=0.if the first character inputted is itself EOF then also len=0 not -1 coz -1 is the value of EOF, it doesn't give u the length of the line.

so when u make cntrl_z in console it will set len to -1 whish will exit loop ? or set it to 0 ?

also one more question why did we increment i after if(c=='\n') isnt this a new string it should add 0 to it before increment ?

Originally Posted by elwad

is bigger than zero means when he reached EOF but EOF is -1 right shouldnt that be -1 not 0 ?

function is return i
it isn't return EOF
when (c=getchar()) ==EOF || c == '\n' it is not enter the loop and go to s[i] = '\0'; if it wasn't read any character (got an EOF from getchar), or it was '\n', i wasn't encreased and equal to zero, s[0] = '\0'; return 0;