3 files changed, 38 insertions, 3 deletions
diff --git a/api/util.c b/api/util.c
index e6f0650..b6f9b49 100644
--- a/api/util.c
+++ b/api/util.c
@@ -4,8 +4,7 @@
 
 UwUVMValue uwuutil_is_type(const char *fnname, UwUVMArgs *args, UwUVMType *type)
 {
-	if (args->num < 1)
-		error("error: %s requires at least one argument\n", fnname);
+	uwuutil_require_min(fnname, args, 1);
 
 	for (size_t i = 0; i < args->num; i++)
 		if (uwuvm_get_arg(args, i).type != type)
@@ -13,3 +12,35 @@ UwUVMValue uwuutil_is_type(const char *fnname, UwUVMArgs *args, UwUVMType *type)
 
 	return uwubool_create(true);
 }
+
+void uwuutil_require_min(const char *fnname, UwUVMArgs *args, size_t n)
+{
+	if (args->num < n) {
+		if (n == 1)
+			error("type error: %s requires at least one optional argument, but none were given\n", fnname);
+		else
+			error("type error: %s requires at least %d arguments, but only %d were given\n", fnname, n, args->num);
+	}
+}
+
+void uwuutil_require_max(const char *fnname, UwUVMArgs *args, size_t n)
+{
+	if (args->num > n) {
+		if (n == 1)
+			error("type error: %s accepts one optional argument, but %d were given\n", fnname, args->num);
+		else
+			error("type error: %s does not take more than %d arguments, but %d were given\n", fnname, args->num);
+	}
+}
+
+void uwuutil_require_exact(const char *fnname, UwUVMArgs *args, size_t n)
+{
+	if (args->num != n) {
+		if (n == 0)
+			error("type error: %s does not take any arguments, but %d were given\n", fnname, args->num);
+		else if (n == 1)
+			error("type error: %s requires exactly one argument, but %d were given\n", fnname, args->num);
+		else
+			error("type error: %s requires exactly %d arguments, but %d were given\n", fnname, n, args->num);
+	}
+}
diff --git a/api/util.h b/api/util.h
index 259f53a..d594107 100644
--- a/api/util.h
+++ b/api/util.h
@@ -4,5 +4,9 @@
 #include "vm.h"
 
 UwUVMValue uwuutil_is_type(const char *fnname, UwUVMArgs *args, UwUVMType *type);
+void uwuutil_require_min  (const char *fnname, UwUVMArgs *args, size_t n);
+void uwuutil_require_max  (const char *fnname, UwUVMArgs *args, size_t n);
+void uwuutil_require_exact(const char *fnname, UwUVMArgs *args, size_t n);
+void uwuutil_require_none (const char *fnname, UwUVMArgs *args);
 
 #endif
diff --git a/api/vm.c b/api/vm.c
index 8374050..52a003c 100644
--- a/api/vm.c
+++ b/api/vm.c
@@ -45,7 +45,7 @@ UwUVMValue uwuvm_evaluate_expression(UwUVMExpression *expression, UwUVMArgs *arg
 
 		case EX_ARGNUM:
 			if ((size_t) expression->value.int_value >= args->num)
-				error("error: not enough arguments (accessed argument $%d, but only %lu arguments were passed)\n", expression->value.int_value, args->num);
+				error("type error: not enough arguments (accessed argument $%d, but only %lu arguments were passed)\n", expression->value.int_value, args->num);
 
 			return uwuvm_clone_value(uwuvm_get_arg(args, expression->value.int_value));