feat(input): make parsing functions generic

Make parsing functions generic with regards to the containers they
return.

Signed-off-by: Matej Focko <mfocko@redhat.com>

src/bin/day03.rs

@@ -29,7 +29,7 @@ struct Day03 {
 }
 impl Solution<Output1, Output2> for Day03 {
     fn new<P: AsRef<Path>>(pathname: P) -> Self {
-        let lines = file_to_lines(pathname);
+        let lines: Vec<String> = file_to_lines(pathname);
 
         let symbols = lines
             .iter()

src/input.rs

@@ -11,18 +11,23 @@ pub fn file_to_string<P: AsRef<Path>>(pathname: P) -> String {
     read_to_string(pathname).expect("Unable to open file")
 }
 
-/// Reads file and returns it as a vector of characters.
-pub fn file_to_chars<P: AsRef<Path>>(pathname: P) -> Vec<char> {
+/// Reads file and returns it as a collection of characters.
+pub fn file_to_chars<B, P: AsRef<Path>>(pathname: P) -> B
+where
+    B: FromIterator<char>,
+{
     read_to_string(pathname)
         .expect("Unable to open file")
         .chars()
         .collect()
 }
 
-/// Reads file and returns a vector of parsed structures. Expects each structure
-/// on its own line in the file. And `T` needs to implement `FromStr` trait.
-pub fn file_to_structs<P: AsRef<Path>, T: FromStr>(pathname: P) -> Vec<T>
+/// Reads file and returns a collection of parsed structures. Expects each
+/// structure on its own line in the file. And `T` needs to implement `FromStr`
+/// trait.
+pub fn file_to_structs<B, P: AsRef<Path>, T: FromStr>(pathname: P) -> B
 where
+    B: FromIterator<T>,
     <T as FromStr>::Err: Debug,
 {
     strings_to_structs(
@@ -32,11 +37,12 @@ where
     )
 }
 
-/// Converts iterator over strings to a vector of parsed structures. `T` needs
-/// to implement `FromStr` trait and its error must derive `Debug` trait.
-pub fn strings_to_structs<T: FromStr, U>(iter: impl Iterator<Item = U>) -> Vec<T>
+/// Converts iterator over strings to a collection of parsed structures. `T`
+/// needs to implement `FromStr` trait and its error must derive `Debug` trait.
+pub fn strings_to_structs<B, T: FromStr, U>(iter: impl Iterator<Item = U>) -> B
 where
-    <T as std::str::FromStr>::Err: std::fmt::Debug,
+    B: FromIterator<T>,
+    <T as FromStr>::Err: Debug,
     U: Deref<Target = str>,
 {
     iter.map(|line| {
@@ -46,8 +52,11 @@ where
     .collect()
 }
 
-/// Reads file and returns it as a vector of its lines.
-pub fn file_to_lines<P: AsRef<Path>>(pathname: P) -> Vec<String> {
+/// Reads file and returns it as a collection of its lines.
+pub fn file_to_lines<B, P: AsRef<Path>>(pathname: P) -> B
+where
+    B: FromIterator<String>,
+{
     read_to_string(pathname)
         .expect("Unable to open file")
         .lines()