[stdlib] pythonic isupper & islower

stdlib/src/builtin/string.mojo

@@ -552,6 +552,21 @@ fn isupper(c: UInt8) -> Bool:
     return _is_ascii_uppercase(c)
 
 
+fn isupper(c: String) -> Bool:
+    """Determines whether the given character is an uppercase character.
+
+    This currently only respects the default "C" locale, i.e. returns True iff
+    the character specified is one of "ABCDEFGHIJKLMNOPQRSTUVWXYZ".
+
+    Args:
+        c: The character to check.
+
+    Returns:
+        True if the character is uppercase.
+    """
+    return _is_ascii_uppercase(ord(c))
+
+
 fn _is_ascii_uppercase(c: UInt8) -> Bool:
     alias ord_a = ord("A")
     alias ord_z = ord("Z")
@@ -578,6 +593,21 @@ fn islower(c: UInt8) -> Bool:
     return _is_ascii_lowercase(c)
 
 
+fn islower(c: String) -> Bool:
+    """Determines whether the given character is an lowercase character.
+
+    This currently only respects the default "C" locale, i.e. returns True iff
+    the character specified is one of "abcdefghijklmnopqrstuvwxyz".
+
+    Args:
+        c: The character to check.
+
+    Returns:
+        True if the character is lowercase.
+    """
+    return _is_ascii_lowercase(ord(c))
+
+
 fn _is_ascii_lowercase(c: UInt8) -> Bool:
     alias ord_a = ord("a")
     alias ord_z = ord("z")
@@ -2193,6 +2223,28 @@ struct String(
                 return False
         return True
 
+    fn islower(self) -> Bool:
+        """Returns True if all characters in the string are lowercase.
+
+        Returns:
+            True if all characters are lowercase else False.
+        """
+        for c in self:
+            if not islower(c):
+                return False
+        return True
+
+    fn isupper(self) -> Bool:
+        """Returns True if all characters in the string are uppercase.
+
+        Returns:
+            True if all characters are uppercase else False.
+        """
+        for c in self:
+            if not isupper(c):
+                return False
+        return True
+
 
 # ===----------------------------------------------------------------------=== #
 # Utilities

stdlib/test/builtin/test_string.mojo

@@ -833,28 +833,52 @@ fn test_splitlines() raises:
 
 fn test_isupper() raises:
     assert_true(isupper(ord("A")))
+    assert_true(isupper("A"))
     assert_true(isupper(ord("B")))
+    assert_true(isupper("B"))
     assert_true(isupper(ord("Y")))
+    assert_true(isupper("Y"))
     assert_true(isupper(ord("Z")))
+    assert_true(isupper("Z"))
 
     assert_false(isupper(ord("A") - 1))
+    assert_false(isupper("a"))
     assert_false(isupper(ord("Z") + 1))
+    assert_false(isupper("z"))
 
     assert_false(isupper(ord("!")))
+    assert_false(isupper("!"))
     assert_false(isupper(ord("0")))
+    assert_false(isupper("0"))
+
+    assert_true(String("ABC").isupper())
+    assert_false(String("abc").isupper())
+    assert_false(String("ABC123").isupper())
 
 
 fn test_islower() raises:
     assert_true(islower(ord("a")))
+    assert_true(islower("a"))
     assert_true(islower(ord("b")))
+    assert_true(islower("b"))
     assert_true(islower(ord("y")))
+    assert_true(islower("y"))
     assert_true(islower(ord("z")))
+    assert_true(islower("z"))
 
     assert_false(islower(ord("a") - 1))
+    assert_false(islower("A"))
     assert_false(islower(ord("z") + 1))
+    assert_false(islower("Z"))
 
     assert_false(islower(ord("!")))
+    assert_false(islower("!"))
     assert_false(islower(ord("0")))
+    assert_false(islower("0"))
+
+    assert_true(String("abc").islower())
+    assert_false(String("ABC").islower())
+    assert_false(String("abc123").islower())
 
 
 fn test_lower() raises: