create VerifyOutput combinator

1 files changed, 39 insertions, 4 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 33d5f34..d0b9cb3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -171,11 +171,21 @@ pub trait Parser<I: Input>: Sized {
         }
     }
 
-    fn verify<C>(self, checker: C) -> impl Parser<I, Output = Self::Output>
+    fn verify_input<C>(self, checker: C) -> impl Parser<I, Output = Self::Output>
     where
         C: Parser<I>,
     {
-        Verify {
+        VerifyInput {
+            parser: self,
+            checker,
+        }
+    }
+
+    fn verify_output<F>(self, checker: F) -> impl Parser<I, Output = Self::Output>
+    where
+        F: Fn(&Self::Output) -> bool,
+    {
+        VerifyOutput {
             parser: self,
             checker,
         }
@@ -827,12 +837,12 @@ where
     Opt { parser }
 }
 
-struct Verify<P, C> {
+struct VerifyInput<P, C> {
     parser: P,
     checker: C,
 }
 
-impl<I, P, C> Parser<I> for Verify<P, C>
+impl<I, P, C> Parser<I> for VerifyInput<P, C>
 where
     I: Input,
     P: Parser<I>,
@@ -854,6 +864,31 @@ where
     }
 }
 
+struct VerifyOutput<P, F> {
+    parser: P,
+    checker: F,
+}
+
+impl<I, P, F> Parser<I> for VerifyOutput<P, F>
+where
+    I: Input,
+    P: Parser<I>,
+    F: Fn(&P::Output) -> bool,
+{
+    type Output = P::Output;
+
+    fn run<OM: Mode, EM: Mode, Tracer: Trace<I>>(
+        &self,
+        it: InputIter<I>,
+    ) -> ParserResult<I, Self::Output, OM, EM> {
+        match self.parser.parse(it.clone()) {
+            Ok((rest, output)) if (self.checker)(&output) => Ok((rest, OM::bind(|| output))),
+            Ok(_) => Err(EM::bind(|| it)),
+            Err(rest) => Err(EM::bind(|| rest)),
+        }
+    }
+}
+
 struct Ignore<P> {
     parser: P,
 }