1 files changed, 26 insertions, 0 deletions
diff --git a/src/ctype/isalpha.c b/src/ctype/isalpha.c
new file mode 100644
index 00000000..2b893425
--- /dev/null
+++ b/src/ctype/isalpha.c
@@ -0,0 +1,26 @@
+#include <ctype.h>
+#include "limits.h"
+#include "nonstd/assert.h"
+
+/** test whether a character is alphabetic **/
+int isalpha(int c)
+{
+	ASSERT_REPRESENTABLE(c, 0, UCHAR_MAX, unsigned char, EOF);
+	/*
+	RETURN(NONZERO, ARGUMENT(c) is an alphabetic character)
+	RETURN(0, ARGUMENT(c) is not an alphabetic character)
+	*/
+	return islower(c) || isupper(c);
+}
+
+/***
+tests whether ARGUMENT(c) is a character in the class
+CHARACTER_CLASS(alpha) in the current locale.
+***/
+
+/*
+LC_CTYPE
+C_LOCALE(`THIS() is true for characters for which FUNCTION(isupper) or FUNCTION(islower) is true')
+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)
+*/