Initial commit

exercises/23_conversions/try_from_into.rs

@@ -0,0 +1,197 @@
+// `TryFrom` is a simple and safe type conversion that may fail in a controlled
+// way under some circumstances. Basically, this is the same as `From`. The main
+// difference is that this should return a `Result` type instead of the target
+// type itself. You can read more about it in the documentation:
+// https://doc.rust-lang.org/std/convert/trait.TryFrom.html
+
+#![allow(clippy::useless_vec)]
+use std::convert::{TryFrom, TryInto};
+
+#[derive(Debug, PartialEq)]
+struct Color {
+    red: u8,
+    green: u8,
+    blue: u8,
+}
+
+// We will use this error type for the `TryFrom` conversions.
+#[derive(Debug, PartialEq)]
+enum IntoColorError {
+    // Incorrect length of slice
+    BadLen,
+    // Integer conversion error
+    IntConversion,
+}
+
+// TODO: Tuple implementation.
+// Correct RGB color values must be integers in the 0..=255 range.
+impl TryFrom<(i16, i16, i16)> for Color {
+    type Error = IntoColorError;
+
+    fn try_from(tuple: (i16, i16, i16)) -> Result<Self, Self::Error> {
+        let (Ok(red), Ok(green), Ok(blue)) = (
+            u8::try_from(tuple.0),
+            u8::try_from(tuple.1),
+            u8::try_from(tuple.2),
+        ) else {
+            return Err(IntoColorError::IntConversion);
+        };
+
+        Ok(Self { red, green, blue })
+    }
+}
+
+// TODO: Array implementation.
+impl TryFrom<[i16; 3]> for Color {
+    type Error = IntoColorError;
+
+    fn try_from(arr: [i16; 3]) -> Result<Self, Self::Error> {
+        Self::try_from((arr[0], arr[1], arr[2]))
+    }
+}
+
+// TODO: Slice implementation.
+// This implementation needs to check the slice length.
+impl TryFrom<&[i16]> for Color {
+    type Error = IntoColorError;
+
+    fn try_from(slice: &[i16]) -> Result<Self, Self::Error> {
+        // Check the length.
+        if slice.len() != 3 {
+            return Err(IntoColorError::BadLen);
+        }
+
+        // Reuse the implementation for a tuple.
+        Self::try_from((slice[0], slice[1], slice[2]))
+    }
+}
+
+fn main() {
+    // Using the `try_from` function.
+    let c1 = Color::try_from((183, 65, 14));
+    println!("{c1:?}");
+
+    // Since `TryFrom` is implemented for `Color`, we can use `TryInto`.
+    let c2: Result<Color, _> = [183, 65, 14].try_into();
+    println!("{c2:?}");
+
+    let v = vec![183, 65, 14];
+    // With slice we should use the `try_from` function
+    let c3 = Color::try_from(&v[..]);
+    println!("{c3:?}");
+    // or put the slice within round brackets and use `try_into`.
+    let c4: Result<Color, _> = (&v[..]).try_into();
+    println!("{c4:?}");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use IntoColorError::*;
+
+    #[test]
+    fn test_tuple_out_of_range_positive() {
+        assert_eq!(Color::try_from((256, 1000, 10000)), Err(IntConversion));
+    }
+
+    #[test]
+    fn test_tuple_out_of_range_negative() {
+        assert_eq!(Color::try_from((-1, -10, -256)), Err(IntConversion));
+    }
+
+    #[test]
+    fn test_tuple_sum() {
+        assert_eq!(Color::try_from((-1, 255, 255)), Err(IntConversion));
+    }
+
+    #[test]
+    fn test_tuple_correct() {
+        let c: Result<Color, _> = (183, 65, 14).try_into();
+        assert!(c.is_ok());
+        assert_eq!(
+            c.unwrap(),
+            Color {
+                red: 183,
+                green: 65,
+                blue: 14,
+            }
+        );
+    }
+
+    #[test]
+    fn test_array_out_of_range_positive() {
+        let c: Result<Color, _> = [1000, 10000, 256].try_into();
+        assert_eq!(c, Err(IntConversion));
+    }
+
+    #[test]
+    fn test_array_out_of_range_negative() {
+        let c: Result<Color, _> = [-10, -256, -1].try_into();
+        assert_eq!(c, Err(IntConversion));
+    }
+
+    #[test]
+    fn test_array_sum() {
+        let c: Result<Color, _> = [-1, 255, 255].try_into();
+        assert_eq!(c, Err(IntConversion));
+    }
+
+    #[test]
+    fn test_array_correct() {
+        let c: Result<Color, _> = [183, 65, 14].try_into();
+        assert!(c.is_ok());
+        assert_eq!(
+            c.unwrap(),
+            Color {
+                red: 183,
+                green: 65,
+                blue: 14
+            }
+        );
+    }
+
+    #[test]
+    fn test_slice_out_of_range_positive() {
+        let arr = [10000, 256, 1000];
+        assert_eq!(Color::try_from(&arr[..]), Err(IntConversion));
+    }
+
+    #[test]
+    fn test_slice_out_of_range_negative() {
+        let arr = [-256, -1, -10];
+        assert_eq!(Color::try_from(&arr[..]), Err(IntConversion));
+    }
+
+    #[test]
+    fn test_slice_sum() {
+        let arr = [-1, 255, 255];
+        assert_eq!(Color::try_from(&arr[..]), Err(IntConversion));
+    }
+
+    #[test]
+    fn test_slice_correct() {
+        let v = vec![183, 65, 14];
+        let c: Result<Color, _> = Color::try_from(&v[..]);
+        assert!(c.is_ok());
+        assert_eq!(
+            c.unwrap(),
+            Color {
+                red: 183,
+                green: 65,
+                blue: 14,
+            }
+        );
+    }
+
+    #[test]
+    fn test_slice_excess_length() {
+        let v = vec![0, 0, 0, 0];
+        assert_eq!(Color::try_from(&v[..]), Err(BadLen));
+    }
+
+    #[test]
+    fn test_slice_insufficient_length() {
+        let v = vec![0, 0];
+        assert_eq!(Color::try_from(&v[..]), Err(BadLen));
+    }
+}