Length conversion (#830)

* feat: length_conversion implemented

* link: added to DIRECTORY.md

* test: zero_to_zero test added

* test: length_of_one_meter added

* fix: apply @vil02 suggestions

* docs: remove redundant comments

---------

Co-authored-by: Piotr Idzik <[email protected]>

DIRECTORY.md

@@ -55,6 +55,7 @@
     * [Hexadecimal To Decimal](https://github.com/TheAlgorithms/Rust/blob/master/src/conversions/hexadecimal_to_decimal.rs)
     * [Octal To Binary](https://github.com/TheAlgorithms/Rust/blob/master/src/conversions/octal_to_binary.rs)
     * [Octal To Decimal](https://github.com/TheAlgorithms/Rust/blob/master/src/conversions/octal_to_decimal.rs)
+    * [Length Conversions](https://github.com/TheAlgorithms/Rust/blob/master/src/conversions/length_conversion.rs)
   * Data Structures
     * [Avl Tree](https://github.com/TheAlgorithms/Rust/blob/master/src/data_structures/avl_tree.rs)
     * [B Tree](https://github.com/TheAlgorithms/Rust/blob/master/src/data_structures/b_tree.rs)

src/conversions/length_conversion.rs

@@ -0,0 +1,94 @@
+/// Author : https://github.com/ali77gh
+/// Conversion of length units.
+///
+/// Available Units:
+/// -> Wikipedia reference: https://en.wikipedia.org/wiki/Millimeter
+/// -> Wikipedia reference: https://en.wikipedia.org/wiki/Centimeter
+/// -> Wikipedia reference: https://en.wikipedia.org/wiki/Meter
+/// -> Wikipedia reference: https://en.wikipedia.org/wiki/Kilometer
+/// -> Wikipedia reference: https://en.wikipedia.org/wiki/Inch
+/// -> Wikipedia reference: https://en.wikipedia.org/wiki/Foot
+/// -> Wikipedia reference: https://en.wikipedia.org/wiki/Yard
+/// -> Wikipedia reference: https://en.wikipedia.org/wiki/Mile
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+pub enum LengthUnit {
+    Millimeter,
+    Centimeter,
+    Meter,
+    Kilometer,
+    Inch,
+    Foot,
+    Yard,
+    Mile,
+}
+
+fn unit_to_meter_multiplier(from: LengthUnit) -> f64 {
+    match from {
+        LengthUnit::Millimeter => 0.001,
+        LengthUnit::Centimeter => 0.01,
+        LengthUnit::Meter => 1.0,
+        LengthUnit::Kilometer => 1000.0,
+        LengthUnit::Inch => 0.0254,
+        LengthUnit::Foot => 0.3048,
+        LengthUnit::Yard => 0.9144,
+        LengthUnit::Mile => 1609.34,
+    }
+}
+
+fn unit_to_meter(input: f64, from: LengthUnit) -> f64 {
+    input * unit_to_meter_multiplier(from)
+}
+
+fn meter_to_unit(input: f64, to: LengthUnit) -> f64 {
+    input / unit_to_meter_multiplier(to)
+}
+
+/// This function will convert a value in unit of [from] to value in unit of [to]
+/// by first converting it to meter and than convert it to destination unit
+pub fn length_conversion(input: f64, from: LengthUnit, to: LengthUnit) -> f64 {
+    meter_to_unit(unit_to_meter(input, from), to)
+}
+
+#[cfg(test)]
+mod length_conversion_tests {
+    use std::collections::HashMap;
+
+    use super::LengthUnit::*;
+    use super::*;
+
+    #[test]
+    fn zero_to_zero() {
+        let units = vec![
+            Millimeter, Centimeter, Meter, Kilometer, Inch, Foot, Yard, Mile,
+        ];
+
+        for u1 in units.clone() {
+            for u2 in units.clone() {
+                assert_eq!(length_conversion(0f64, u1, u2), 0f64);
+            }
+        }
+    }
+
+    #[test]
+    fn length_of_one_meter() {
+        let meter_in_different_units = HashMap::from([
+            (Millimeter, 1000f64),
+            (Centimeter, 100f64),
+            (Kilometer, 0.001f64),
+            (Inch, 39.37007874015748f64),
+            (Foot, 3.280839895013123f64),
+            (Yard, 1.0936132983377078f64),
+            (Mile, 0.0006213727366498068f64),
+        ]);
+        for (input_unit, input_value) in &meter_in_different_units {
+            for (target_unit, target_value) in &meter_in_different_units {
+                assert!(
+                    num_traits::abs(
+                        length_conversion(*input_value, *input_unit, *target_unit) - *target_value
+                    ) < 0.0000001
+                );
+            }
+        }
+    }
+}

src/conversions/mod.rs

@@ -4,6 +4,7 @@ mod decimal_to_binary;
 mod decimal_to_hexadecimal;
 mod hexadecimal_to_binary;
 mod hexadecimal_to_decimal;
+mod length_conversion;
 mod octal_to_binary;
 mod octal_to_decimal;
 pub use self::binary_to_decimal::binary_to_decimal;
@@ -12,5 +13,6 @@ pub use self::decimal_to_binary::decimal_to_binary;
 pub use self::decimal_to_hexadecimal::decimal_to_hexadecimal;
 pub use self::hexadecimal_to_binary::hexadecimal_to_binary;
 pub use self::hexadecimal_to_decimal::hexadecimal_to_decimal;
+pub use self::length_conversion::length_conversion;
 pub use self::octal_to_binary::octal_to_binary;
 pub use self::octal_to_decimal::octal_to_decimal;