diff --git a/src/combinators/map.rs b/src/combinators/map.rs
new file mode 100644
index 0000000..0d72d5a
--- /dev/null
+++ b/src/combinators/map.rs
@@ -0,0 +1,14 @@
+use crate::parser::{Parser, ParserInput};
+
+pub fn map<P, F, I, O1, O2, E>(parser: P, map_fn: F) -> impl Parser<I, O2, E>
+where
+    I: ParserInput,
+    P: Parser<I, O1, E>,
+    F: Fn(O1) -> O2,
+{
+    move |input| {
+        parser
+            .parse(input)
+            .map(|(result, rest)| (map_fn(result), rest))
+    }
+}
diff --git a/src/combinators/mod.rs b/src/combinators/mod.rs
index 6ea5292..364df44 100644
--- a/src/combinators/mod.rs
+++ b/src/combinators/mod.rs
@@ -1,194 +1,16 @@
-use crate::parser::{BoxedParser, ParseResult, Parser, ParserInput};
+mod map;
+mod optional;
+mod repeated;
+mod separated_by;
 
-pub fn optional<P, I, O, E>(parser: P) -> impl Parser<I, Option<O>, E>
-where
-    P: Parser<I, O, E>,
-    I: ParserInput + Clone,
-{
-    move |input: I| match parser.parse(input.clone()) {
-        Ok((output, rest)) => Ok((Some(output), rest)),
-        Err(_e) => Ok((None, input)),
-    }
-}
-
-pub fn map<P, F, I, O1, O2, E>(parser: P, map_fn: F) -> impl Parser<I, O2, E>
-where
-    I: ParserInput,
-    P: Parser<I, O1, E>,
-    F: Fn(O1) -> O2,
-{
-    move |input| {
-        parser
-            .parse(input)
-            .map(|(result, rest)| (map_fn(result), rest))
-    }
-}
-
-pub struct Repeated<'a, I, O>
-where
-    I: ParserInput + Clone,
-{
-    inner_parser: BoxedParser<'a, I, O, I>,
-    at_least: Option<u16>,
-    at_most: Option<u16>,
-}
-
-impl<'a, I, O> Repeated<'a, I, O>
-where
-    I: ParserInput + Clone,
-{
-    pub fn at_least(self, n: u16) -> Self {
-        Self {
-            at_least: Some(n),
-            ..self
-        }
-    }
-    pub fn at_most(self, n: u16) -> Self {
-        Self {
-            at_most: Some(n),
-            ..self
-        }
-    }
-
-    pub fn separated_by<D, O2>(self, delimiter: D, allow_trailing: bool) -> SeparatedBy<'a, I, O>
-    where
-        D: Parser<I, O2, I> + 'a,
-        O2: 'a,
-        I: 'a,
-    {
-        SeparatedBy {
-            inner_repeated: self,
-            delimiter: BoxedParser::new(delimiter.to(())),
-            allow_trailing,
-        }
-    }
-}
-
-impl<'a, I, O> Parser<I, Vec<O>, I> for Repeated<'a, I, O>
-where
-    I: ParserInput + Clone + 'a,
-{
-    fn parse(&self, input: I) -> ParseResult<I, Vec<O>, I> {
-        let at_least = self.at_least.unwrap_or(0);
-        let at_most = self.at_most.unwrap_or(u16::MAX);
-
-        if at_most == 0 {
-            return Ok((vec![], input));
-        }
-
-        let mut results = Vec::new();
-        let mut count: u16 = 0;
-        let mut further_input = input.clone();
-
-        while let Ok((item, rest)) = self.inner_parser.parse(further_input.clone()) {
-            results.push(item);
-            further_input = rest;
-            count += 1;
-            if count >= at_most {
-                break;
-            }
-        }
-        if count < at_least {
-            return Err(input);
-        }
-
-        Ok((results, further_input))
-    }
-}
-
-pub struct SeparatedBy<'a, I, O>
-where
-    I: ParserInput + Clone,
-{
-    inner_repeated: Repeated<'a, I, O>,
-    delimiter: BoxedParser<'a, I, (), I>,
-    allow_trailing: bool,
-}
-
-impl<'a, I, O> Parser<I, Vec<O>, I> for SeparatedBy<'a, I, O>
-where
-    I: ParserInput + Clone + 'a,
-{
-    fn parse(&self, input: I) -> ParseResult<I, Vec<O>, I> {
-        let at_least = self.inner_repeated.at_least.unwrap_or(0);
-        let at_most = self.inner_repeated.at_most.unwrap_or(u16::MAX);
-        let parser = &self.inner_repeated.inner_parser;
-        let delimiter = &self.delimiter;
-
-        if at_most == 0 {
-            return Ok((vec![], input));
-        }
-
-        let mut results = Vec::new();
-        let mut count: u16 = 0;
-        let mut further_input;
-
-        match parser.parse(input.clone()) {
-            Ok((item, rest)) => {
-                results.push(item);
-                further_input = rest;
-            }
-            Err(_e) => {
-                if at_least > 0 {
-                    return Err(input);
-                } else {
-                    return Ok((vec![], input));
-                }
-            }
-        }
-
-        loop {
-            match delimiter.parse(further_input.clone()) {
-                Ok(((), rest)) => {
-                    further_input = rest;
-                }
-                Err(_e) => {
-                    break;
-                }
-            }
-
-            match parser.parse(further_input.clone()) {
-                Ok((item, rest)) => {
-                    results.push(item);
-                    further_input = rest;
-                    count += 1;
-                }
-                Err(_e) if self.allow_trailing => {
-                    break;
-                }
-                Err(e) => {
-                    return Err(e);
-                }
-            }
-
-            if count >= at_most {
-                break;
-            }
-        }
-
-        if count < at_least {
-            return Err(input);
-        }
-
-        Ok((results, further_input))
-    }
-}
-
-pub fn repeated<'a, P, I, O>(parser: P) -> Repeated<'a, I, O>
-where
-    P: Parser<I, O, I> + 'static,
-    I: ParserInput + Clone + 'static,
-{
-    Repeated {
-        inner_parser: BoxedParser::new(parser),
-        at_least: None,
-        at_most: None,
-    }
-}
+pub use map::map;
+pub use optional::optional;
+pub use repeated::repeated;
 
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::parser::Parser;
     use crate::primitives::literal;
 
     #[test]
diff --git a/src/combinators/optional.rs b/src/combinators/optional.rs
new file mode 100644
index 0000000..c630268
--- /dev/null
+++ b/src/combinators/optional.rs
@@ -0,0 +1,12 @@
+use crate::parser::{Parser, ParserInput};
+
+pub fn optional<P, I, O, E>(parser: P) -> impl Parser<I, Option<O>, E>
+where
+    P: Parser<I, O, E>,
+    I: ParserInput + Clone,
+{
+    move |input: I| match parser.parse(input.clone()) {
+        Ok((output, rest)) => Ok((Some(output), rest)),
+        Err(_e) => Ok((None, input)),
+    }
+}
diff --git a/src/combinators/repeated.rs b/src/combinators/repeated.rs
new file mode 100644
index 0000000..2b1c35c
--- /dev/null
+++ b/src/combinators/repeated.rs
@@ -0,0 +1,86 @@
+use crate::combinators::separated_by::SeparatedBy;
+use crate::parser::{BoxedParser, ParseResult, Parser, ParserInput};
+
+pub fn repeated<'a, P, I, O>(parser: P) -> Repeated<'a, I, O>
+where
+    P: Parser<I, O, I> + 'static,
+    I: ParserInput + Clone + 'static,
+{
+    Repeated {
+        inner_parser: BoxedParser::new(parser),
+        at_least: None,
+        at_most: None,
+    }
+}
+
+pub struct Repeated<'a, I, O>
+where
+    I: ParserInput + Clone,
+{
+    pub(super) inner_parser: BoxedParser<'a, I, O, I>,
+    pub(super) at_least: Option<u16>,
+    pub(super) at_most: Option<u16>,
+}
+
+impl<'a, I, O> Repeated<'a, I, O>
+where
+    I: ParserInput + Clone,
+{
+    pub fn at_least(self, n: u16) -> Self {
+        Self {
+            at_least: Some(n),
+            ..self
+        }
+    }
+    pub fn at_most(self, n: u16) -> Self {
+        Self {
+            at_most: Some(n),
+            ..self
+        }
+    }
+
+    pub fn separated_by<D, O2>(self, delimiter: D, allow_trailing: bool) -> SeparatedBy<'a, I, O>
+    where
+        D: Parser<I, O2, I> + 'a,
+        O2: 'a,
+        I: 'a,
+    {
+        SeparatedBy {
+            inner_repeated: self,
+            delimiter: BoxedParser::new(delimiter.to(())),
+            allow_trailing,
+        }
+    }
+}
+
+impl<'a, I, O> Parser<I, Vec<O>, I> for Repeated<'a, I, O>
+where
+    I: ParserInput + Clone + 'a,
+{
+    fn parse(&self, input: I) -> ParseResult<I, Vec<O>, I> {
+        let at_least = self.at_least.unwrap_or(0);
+        let at_most = self.at_most.unwrap_or(u16::MAX);
+
+        if at_most == 0 {
+            return Ok((vec![], input));
+        }
+
+        let mut results = Vec::new();
+        let mut count: u16 = 0;
+        let mut further_input = input.clone();
+
+        while let Ok((item, rest)) = self.inner_parser.parse(further_input.clone()) {
+            results.push(item);
+            further_input = rest;
+            count += 1;
+            if count >= at_most {
+                break;
+            }
+        }
+        if count < at_least {
+            return Err(input);
+        }
+
+        Ok((results, further_input))
+    }
+}
diff --git a/src/combinators/separated_by.rs b/src/combinators/separated_by.rs
new file mode 100644
index 0000000..3c2350b
--- /dev/null
+++ b/src/combinators/separated_by.rs
@@ -0,0 +1,80 @@
+use crate::combinators::repeated::Repeated;
+use crate::parser::{BoxedParser, ParseResult, Parser, ParserInput};
+
+pub struct SeparatedBy<'a, I, O>
+where
+    I: ParserInput + Clone,
+{
+    pub(super) inner_repeated: Repeated<'a, I, O>,
+    pub(super) delimiter: BoxedParser<'a, I, (), I>,
+    pub(super) allow_trailing: bool,
+}
+
+impl<'a, I, O> Parser<I, Vec<O>, I> for SeparatedBy<'a, I, O>
+where
+    I: ParserInput + Clone + 'a,
+{
+    fn parse(&self, input: I) -> ParseResult<I, Vec<O>, I> {
+        let at_least = self.inner_repeated.at_least.unwrap_or(0);
+        let at_most = self.inner_repeated.at_most.unwrap_or(u16::MAX);
+        let parser = &self.inner_repeated.inner_parser;
+        let delimiter = &self.delimiter;
+
+        if at_most == 0 {
+            return Ok((vec![], input));
+        }
+
+        let mut results = Vec::new();
+        let mut count: u16 = 0;
+        let mut further_input;
+
+        match parser.parse(input.clone()) {
+            Ok((item, rest)) => {
+                results.push(item);
+                further_input = rest;
+            }
+            Err(_e) => {
+                if at_least > 0 {
+                    return Err(input);
+                } else {
+                    return Ok((vec![], input));
+                }
+            }
+        }
+
+        loop {
+            match delimiter.parse(further_input.clone()) {
+                Ok(((), rest)) => {
+                    further_input = rest;
+                }
+                Err(_e) => {
+                    break;
+                }
+            }
+
+            match parser.parse(further_input.clone()) {
+                Ok((item, rest)) => {
+                    results.push(item);
+                    further_input = rest;
+                    count += 1;
+                }
+                Err(_e) if self.allow_trailing => {
+                    break;
+                }
+                Err(e) => {
+                    return Err(e);
+                }
+            }
+
+            if count >= at_most {
+                break;
+            }
+        }
+
+        if count < at_least {
+            return Err(input);
+        }
+
+        Ok((results, further_input))
+    }
+}