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#include <stdio.h>
/* The C Programming Language: 2nd Edition
*
* Exercise 1-23: Write a program to remove all comments from a C program.
* Don't forget to handle quoted strings and character constants properly. C
* comments do not nest.
*
* Answer: At first I didn't know why it was important to account for strings
* or character constants. The reason behind this is that /* and // are valid
* inside those parts of C, so they deserve special treatment.
*
* The states for this program are IN_MULTI for a multi-line comment,
* IN_SINGLE for a single line comment, OUT for being outside a comment, and
* IN_STRING for being inside a string or character constant. These four states
* are all I need to determine whether I should output the contents of the C
* file or not. Characters are only output when the state is OUT or IN_STRING,
* and there are conditions for getting into and out of comment state.
*
* This structure is known as a finite state machine (FSM).
*/
#define OUT 0
#define IN_MULTI 1
#define IN_SINGLE 2
#define IN_STRING 3
char c, p;
int status;
int main() {
// Treat input like a stream, since that's all the K&R has explained so far.
while ((c = getchar()) != EOF) {
/* This is to account for strings and character constants */
if (c == '\'' || c == '"') {
if (status == OUT) {
status = IN_STRING;
} else if (status == IN_STRING) {
status = OUT;
}
}
// Check for the ways to open a comment, and set state accordingly
if (c == '/' && status == OUT) {
// Look ahead and store the character that's returned
p = getchar();
if (p == '*') {
status = IN_MULTI;
} else if (p == '/') {
status = IN_SINGLE;
} else {
putchar(c);
putchar(p);
continue;
}
}
// Ignore everything in a single line comment until a newline
if (status == IN_SINGLE) {
if (c == '\n') {
putchar(c);
status = OUT;
continue;
}
}
// Ignore everything until you reach the end of a multi comment
if (status == IN_MULTI && c == '*') {
p = getchar();
if (p == '/') {
status = OUT;
continue;
}
}
// Output everything when we're not in a comment!
if (status == OUT || status == IN_STRING) {
putchar(c);
}
}
/* derpsauce
*
*
* Testing comment for the lulz. lolololol
*/
}
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