diff --git a/src/primitives.rs b/src/primitives.rs
index df5c25f..b322b81 100644
--- a/src/primitives.rs
+++ b/src/primitives.rs
@@ -21,6 +21,18 @@ pub fn any_char(input: &str) -> ParseResult<&str, char, &str> {
     }
 }
 
+pub fn one_of<'a>(items: &'static str) -> impl Parser<&'a str, &'a str, &'a str> {
+    move |input: &'a str| {
+        if let Some(ch) = input.chars().nth(0) {
+            if items.contains(ch) {
+                let (first, rest) = input.split_at(1);
+                return Ok((first, rest));
+            }
+        }
+        Err(input)
+    }
+}
+
 pub fn pred<P, F, I, O>(parser: P, pred_fn: F) -> impl Parser<I, O, I>
 where
     P: Parser<I, O, I>,