1 files changed, 30 insertions, 0 deletions
diff --git a/src/ctype/islower.c b/src/ctype/islower.c
new file mode 100644
index 00000000..082697dd
--- /dev/null
+++ b/src/ctype/islower.c
@@ -0,0 +1,30 @@
+#include <ctype.h>
+#include "limits.h"
+#include "nonstd/assert.h"
+#include "nonstd/internal.h"
+#include "nonstd/ctype.h"
+
+/** test whether a character is a lowercase letter **/
+int islower(int c)
+{
+	unsigned int *map = __libc(CTYPE);
+
+	ASSERT_REPRESENTABLE(c, 0, UCHAR_MAX, unsigned char, EOF);
+	/*
+	RETURN(NONZERO, ARGUMENT(c) is a lowercase letter);
+	RETURN(0, ARGUMENT(c) is not a lowercase letter);
+	*/
+	return map[c] & LOWER;
+}
+
+/***
+tests whether ARGUMENT(c) is a character in the class CHARACTER_CLASS(lower)
+in the current locale.
+***/
+
+/*
+LC_CTYPE
+C_LOCALE(`THIS() is true for the characters CHAR(a), CHAR(b), CHAR(c), CHAR(d), CHAR(e), CHAR(f), CHAR(g), CHAR(h), CHAR(i), CHAR(j), CHAR(k), CHAR(l), CHAR(m), CHAR(n), CHAR(o), CHAR(p), CHAR(q), CHAR(s), CHAR(t), CHAR(u), CHAR(w), CHAR(x), CHAR(y), and CHAR(z)')
+OTHER_LOCALES(`THIS() is true for a set of characters for which none of FUNCTION(iscntrl), FUNCTION(isdigit), FUNCTION(ispunct), or FUNCTION(isspace) is true')
+STDC(1)
+*/