Add exercise descriptions and answers for ch1

* Corrected behavior in solutions for 1-9 and 1-23

1 files changed, 24 insertions, 16 deletions

diff --git a/ch1/1-23_decomment.c b/ch1/1-23_decomment.c
index 63193cd..d9c5c90 100644
--- a/ch1/1-23_decomment.c
+++ b/ch1/1-23_decomment.c
@@ -1,28 +1,29 @@
 #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."
  *
- * I'm not sure why the instructions tell the reader to account for quoted
- * strings and character constants. Comments always begin with either // or
- * /*, so that sets the boundary of state.
+ * 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, and OUT for being outside a comment.
- * These three 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, and there are conditions for getting into and out of comment state.
+ * 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.
  *
- * I don't know of any other way to do this without invoking some higher-level
- * libraries.
+ * This structure is known as a finite state machine (FSM).
  */
 
+#define OUT       0
 #define IN_MULTI  1
 #define IN_SINGLE 2
-#define OUT       0
+#define IN_STRING 3
 
 char c, p;
 int status;
@@ -30,7 +31,14 @@ 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
@@ -70,7 +78,7 @@ int main() {
 		}
 
 		// Output everything when we're not in a comment!
-		if (status == OUT) {
+		if (status == OUT || status == IN_STRING) {
 			putchar(c);
 		}