1 files changed, 29 insertions, 0 deletions
diff --git a/src/ctype/tolower.c b/src/ctype/tolower.c
new file mode 100644
index 00000000..b684eb7a
--- /dev/null
+++ b/src/ctype/tolower.c
@@ -0,0 +1,29 @@
+#include <ctype.h>
+#include "limits.h"
+#include "nonstd/assert.h"
+#include "nonstd/ctype.h"
+#include "nonstd/internal.h"
+
+/** convert an uppercase letter to lowercase **/
+int tolower(int c)
+{
+	unsigned char *map = __libc(TOLOWER);
+
+	ASSERT_REPRESENTABLE(c, 0, UCHAR_MAX, unsigned char, EOF);
+	/*
+	RETURN_SUCCESS(ARGUMENT(c) converted to lowercase);
+	RETURN_FAILURE(ARGUMENT(c), ARGUMENT(c) was not an uppercase letter or it has no equivalent lowercase letter);
+	*/
+
+	return map[c];
+}
+
+/***
+converts an uppercase letter to its equivalent lowercase letter in the current
+locale.
+***/
+
+/*
+LC_CTYPE
+STDC(1)
+*/