add: TryParser and SatifiedMapParser.

src/parser.rs

@@ -3,11 +3,11 @@ mod primitive_parsers;
 
 use crate::parser::modified_parsers::{
     BindParser, ConvertParser, LitervalCountParser, LitervalParser, LookAheadParser, MapParser,
-    NextParser, ReverseParser,
+    NextParser, ReverseParser, TryParser,
 };
 use crate::parser::primitive_parsers::{
-    AnyParser, FailParser, FailWithMessageParser, SatisfyParser, SkipParser, SucceedParser,
+    AnyParser, FailParser, FailWithMessageParser, SatifiedMapParser, SatisfyParser, SkipParser,
-    TakeParser,
+    SucceedParser, TakeParser,
 };
 use std::cell::RefCell;
 use std::error::Error;
@@ -178,6 +178,17 @@ where
         }
     }
 
+    fn try_parse(self, result: T) -> TryParser<Self, T>
+    where
+        Self: Sized,
+        T: Clone,
+    {
+        TryParser {
+            parser: self,
+            result,
+        }
+    }
+
     fn reverse<TResult>(self, result: TResult) -> ReverseParser<Self, T, TResult>
     where
         Self: Sized,
@@ -259,6 +270,16 @@ where
     SatisfyParser { predicate }
 }
 
+pub fn satified_map<'a, TToken, TContext, T: 'a, F>(
+    mapper: F,
+) -> impl Parser<'a, TToken, T, TContext>
+where
+    TToken: Debug + Clone,
+    F: Fn(&TToken) -> Option<T>,
+{
+    SatifiedMapParser { mapper }
+}
+
 pub fn any<'a, TToken, TContext>() -> impl Parser<'a, TToken, TToken, TContext>
 where
     TToken: Debug + Clone + 'a,

src/parser/modified_parsers.rs

@@ -189,6 +189,29 @@ where
     }
 }
 
+pub struct TryParser<P, T> {
+    pub(crate) parser: P,
+    pub(crate) result: T,
+}
+
+impl<'a, TToken, T, TContext, P> Parser<'a, TToken, T, TContext> for TryParser<P, T>
+where
+    TToken: Debug + Clone,
+    T: Clone + 'a,
+    P: Parser<'a, TToken, T, TContext>,
+{
+    fn parse(
+        &self,
+        context: Rc<RefCell<ParserContext<TToken, TContext>>>,
+        input: &'a [TToken],
+    ) -> ParserResult<'a, TToken, T> {
+        match self.parser.parse(context, input) {
+            Err(r) => Ok((r.input, self.result.clone())),
+            r => r,
+        }
+    }
+}
+
 pub struct ReverseParser<P, T, TResult> {
     pub(crate) parser: P,
     pub(crate) result: TResult,
@@ -370,6 +393,17 @@ mod test {
         });
     }
 
+    #[test]
+    fn try_parse_test() {
+        parser_test_helper(ParserContext::new_with_str("abc", ()), &'a', |c, i| {
+            char_parser('a').try_parse('a').parse(c, i)
+        });
+
+        parser_test_helper(ParserContext::new_with_str("bc", ()), &'a', |c, i| {
+            char_parser('a').try_parse('a').parse(c, i)
+        });
+    }
+
     #[test]
     fn reverse_test() {
         parser_test_helper(ParserContext::new_with_str("abc", ()), &(), |c, i| {

src/parser/primitive_parsers.rs

@@ -86,6 +86,32 @@ where
     }
 }
 
+pub struct SatifiedMapParser<F> {
+    pub(crate) mapper: F,
+}
+
+impl<'a, TToken, TContext, T: 'a, F> Parser<'a, TToken, T, TContext> for SatifiedMapParser<F>
+where
+    TToken: Debug + Clone,
+    F: Fn(&TToken) -> Option<T>,
+{
+    fn parse(
+        &self,
+        _: Rc<RefCell<ParserContext<TToken, TContext>>>,
+        input: &'a [TToken],
+    ) -> ParserResult<'a, TToken, T> {
+        if input.is_empty() {
+            return Err(FailedParserResult::new_with_str(input, "Input is empty"));
+        }
+
+        if let Some(result) = (self.mapper)(&input[0]) {
+            Ok((&input[1..], result))
+        } else {
+            Err(FailedParserResult::new_with_str(input, "Predicate failed."))
+        }
+    }
+}
+
 pub struct AnyParser {}
 
 impl<'a, TToken, TContext> Parser<'a, TToken, TToken, TContext> for AnyParser
@@ -166,8 +192,8 @@ where
 mod test {
     use super::*;
     use crate::parser::{
-        any, fail, fail_with_message, failed_parser_test_helper, parser_test_helper, satisfy, skip,
+        any, fail, fail_with_message, failed_parser_test_helper, parser_test_helper, satified_map,
-        succeed, take,
+        satisfy, skip, succeed, take,
     };
 
     #[test]
@@ -202,6 +228,21 @@ mod test {
         });
     }
 
+    #[test]
+    fn satified_map_test() {
+        parser_test_helper(ParserContext::new_with_str("123", ()), &1, |c, i| {
+            satified_map(|x: &char| x.to_digit(10)).parse(c, i)
+        });
+
+        parser_test_helper(ParserContext::new_with_str("23", ()), &2, |c, i| {
+            satified_map(|x: &char| x.to_digit(10)).parse(c, i)
+        });
+
+        parser_test_helper(ParserContext::new_with_str("3", ()), &3, |c, i| {
+            satified_map(|x: &char| x.to_digit(10)).parse(c, i)
+        });
+    }
+
     #[test]
     fn any_test() {
         parser_test_helper(ParserContext::new_with_str("abc", ()), &'a', |c, i| {