Solve exercise 1-23: Remove C comments

1 files changed, 84 insertions, 0 deletions

diff --git a/1-23_decomment.c b/1-23_decomment.c
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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."
+ *
+ * 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.
+ *
+ * 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.
+ *
+ * I don't know of any other way to do this without invoking some higher-level
+ * libraries.
+ */
+
+#define IN_MULTI  1
+#define IN_SINGLE 2
+#define OUT       0
+
+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) {
+
+		// 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) {
+			putchar(c);
+		}
+
+	}
+
+	/* derpsauce
+	 *
+	 *
+	 * Testing comment for the lulz. lolololol
+	 */
+}