diff --git a/src/str.c b/src/str.c
index 73bb911..d6a89c3 100644
--- a/src/str.c
+++ b/src/str.c
@@ -20,11 +20,11 @@
 #include <ctype.h>
 #include <stddef.h> /* NULL */
 #include <stdio.h> /* fprintf(3) */
-#include <stdlib.h> /* EXIT_FAILURE */
+#include <stdlib.h> /* size_t, EXIT_FAILURE */
 #include <string.h> /* strcmp(3) */
-#include <sysexits.h>
+#include <sysexits.h> /* EX_USAGE */
 
-static char *program_name = "str";
+char *program_name = "str";
 
 static struct {
 	char *name;
@@ -41,41 +41,41 @@ static struct {
 	{ "isprint", isprint },
 	{ "ispunct", ispunct },
 	{ "isspace", isspace },
-	{ "isupper", isupper }
+	{ "isupper", isupper },
+	{ NULL, NULL } /* marks end */
 };
 
+int usage(char *s){
+	fprintf(stderr, "Usage: %s type string...\n", s);
+	return EX_USAGE;
+}
+
 int main(int argc, char *argv[]){
-	int ctype;
-	int i;
-	int r;
+	size_t ctype; /* selected from ctypes.h; index of ctype */
+	int retval;
 
-	if (argc >= 3) {
-		for (ctype = 0; ctype < (sizeof ctypes) / (sizeof *ctypes); ++ctype) {
-			if(strcmp(argv[1], ctypes[ctype].name) == 0) {
-				goto pass;
-			}
-		}
-	}
+	if (argc < 3) { return usage(argv[0] == NULL ? program_name : argv[0]); }
 
-	fprintf(
-		stderr,
-		"Usage: %s type string...\n",
-		argv[0] == NULL ? program_name : argv[0]
+	for ( /* iterate ctypes */
+		ctype = 0;
+		ctypes[ctype].f != NULL /* break at the end of ctypes */
+			&& strcmp(argv[1], ctypes[ctype].name) != 0; /* break at match */
+		++ctype
 	);
 
-	return EX_USAGE;
+	if (ctypes[ctype].f == NULL) { return usage(argv[0]); }
 
-pass:	for (argv += 2, r = 1; *argv != NULL; ++argv) {
-		for (i = 0; argv[0][i] != '\0'; ++i) {
-			/* First checks if argv[0][i] is valid ASCII; ctypes(3)
-			 * don't handle non-ASCII.
-			 * This is bad. */
+	/* iterate args */
+	for (argv += 2, retval = EXIT_FAILURE; *argv != NULL; ++argv) {
+		for (size_t i = 0; argv[0][i] != '\0'; ++i) { /* iterate arg bytes */
+			/* First checks if argv[0][i] is valid ASCII; ctypes(3) don't
+			 * handle non-ASCII. This is bad. */
 			if(
 				(unsigned char)argv[0][i] < 0x80 && !ctypes[ctype].f(argv[0][i])
-			) { return 1; }
-			else { r = 0; }
+			) { return EXIT_FAILURE; }
+			else { retval = EXIT_SUCCESS; }
 		}
 	}
 
-	return r;
+	return retval;
 }