feat: add generics3

Author: solomoncyj

exercises/14_generics/generics3.rs

@@ -0,0 +1,28 @@
+
+//fn avg<???>(???) -> ???
+//TODO: write a fuction that takes in a slice of number-like primitives, eg u8, i16, usize
+//      and returns the mean of the slice
+//      you do not to implement  this for floats due to a language limitation
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+//you may add `.unwrap()` to the avg fuction calls if needed
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_u8() {
+        let input: [u8; 5] = [2, 4, 6, 8, 10];
+        let ans: u8 = avg(&input);
+        assert_eq!(ans, 6);
+    }
+
+    fn test_f32() {
+        let input: [i32; 5] = [546, 263, 8764, 4198, 7654];
+        let ans: i32 = avg(&input);
+        assert_eq!(ans, 4285);
+    }
+}

rustlings-macros/info.toml

@@ -736,6 +736,20 @@ hint = """
 Related section in The Book:
 https://doc.rust-lang.org/book/ch10-01-syntax.html#in-method-definitions"""
 
+[[exercises]]
+name = "generics3"
+dir = "14_generics"
+hint = """
+The fuction should have the required traits for the division,
+eg Div to divide the total and size of slice, Sum to sum over the slice
+and TryFrom as `as T` is disallowed in generic contexs
+
+You may find the following links usefull:
+https://doc.rust-lang.org/std/ops/trait.Div.html
+https://doc.rust-lang.org/std/iter/trait.Sum.html
+https://doc.rust-lang.org/std/convert/trait.TryFrom.html
+"""
+
 # TRAITS
 
 [[exercises]]

solutions/14_generics/generics3.rs

@@ -0,0 +1,38 @@
+use std::iter::Sum;
+use std::num::TryFrom;
+use std::ops::Div;
+
+//use Div as we need to div sum by size of slice &[T]
+//Use Sum so that .sum() can be used
+//Use Copy as .map() requires it
+//use TryFrom to use T::try_from as `as T` is not allowed
+
+fn avg<T>(input: &[T]) -> Result<T, <T as TryFrom<usize>>::Error>
+where
+    T: Div<Output = T> + Sum + TryFrom<usize> + Copy,
+{
+    Ok(input.iter().map(|x| *x).sum::<T>() / T::try_from(input.len())?)
+}
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+//you may add `.unwrap()` to the avg fuction calls if needed
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_u8() {
+        let input: [u8; 5] = [2, 4, 6, 8, 10];
+        let ans: u8 = avg(&input).unwrap();
+        assert_eq!(ans, 6);
+    }
+
+    fn test_f32() {
+        let input: [i32; 5] = [546, 263, 8764, 4198, 7654];
+        let ans: i32 = avg(&input).unwrap();
+        assert_eq!(ans, 4285);
+    }
+}