add: string_parser and char_satisfy parser.

src/text/string_parsers.rs

@@ -0,0 +1,37 @@
+use crate::parser::{FailedParserResult, Parser, ParserContext, ParserResult};
+use std::cell::RefCell;
+use std::rc::Rc;
+
+pub struct StringParser {
+    pub(crate) str: &'static str,
+}
+
+impl<'a, TContext> Parser<'a, char, &'a [char], TContext> for StringParser {
+    fn parse(
+        &self,
+        _: Rc<RefCell<ParserContext<char, TContext>>>,
+        input: &'a [char],
+    ) -> ParserResult<'a, char, &'a [char]> {
+        let length = self.str.chars().count();
+        if input.len() < length {
+            return Err(FailedParserResult::new(
+                input,
+                format!("Failed to get enough elements for string '{}'.", self.str),
+            ));
+        }
+
+        if (&input[..length])
+            .iter()
+            .zip(self.str.chars())
+            .map(|(x, y)| *x == y)
+            .all(|x| x)
+        {
+            Ok((&input[length..], &input[..length]))
+        } else {
+            Err(FailedParserResult::new(
+                input,
+                format!("Input is not string '{}'", self.str),
+            ))
+        }
+    }
+}