fix: apply @vil02 suggestions

Author: ali77gh

src/conversions/length_conversion.rs

@@ -29,37 +29,35 @@ pub enum LengthUnit {
 /// It's gonna be 56 functions or 56 cases in match statement
 /// It's hard to write code for every unit to unit so I solve this problem
 /// by converting input to meter and than convert it to output
-impl LengthUnit {
-    /// This function give you a number (let's call it n)
-    /// So if you multiple a value in this unit to n you will get meters
-    ///
-    /// m * in-unit = meter
-    fn get_unit_to_meter_multiplier(&self) -> f64 {
-        match self {
-            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,
-        }
+/// This function give you a number (let's call it n)
+/// So if you multiple a value in this unit to n you will get meters
+///
+/// m * in-unit = meter
+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,
     }
+}
 
-    /// This function give you a number (let's call it n)
-    /// So if you multiple a value in meters to n you will get unit
-    ///
-    /// m * meter = in-unit
-    fn get_unit_from_meter_multiplier(&self) -> f64 {
-        1.0 / self.get_unit_to_meter_multiplier()
-    }
+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 {
-    input * from.get_unit_to_meter_multiplier() * to.get_unit_from_meter_multiplier()
+    meter_to_unit(unit_to_meter(input, from), to)
 }
 
 #[cfg(test)]
@@ -69,44 +67,6 @@ mod length_conversion_tests {
     use super::LengthUnit::*;
     use super::*;
 
-    #[test]
-    fn meter_to_other() {
-        assert_eq!(length_conversion(4f64, Meter, Millimeter), 4000.0);
-        assert_eq!(length_conversion(4f64, Meter, Foot), 13.123359580052492);
-        assert_eq!(length_conversion(1.0, Meter, Kilometer), 0.001);
-    }
-
-    #[test]
-    fn other_to_meter() {
-        assert_eq!(length_conversion(4f64, Millimeter, Meter), 0.004);
-        assert_eq!(length_conversion(2.0, Foot, Meter), 0.6096);
-        assert_eq!(length_conversion(1.0, Inch, Meter), 0.0254);
-        assert_eq!(length_conversion(4.0, Yard, Meter), 3.6576);
-        assert_eq!(length_conversion(3.0, Foot, Meter), 0.9144000000000001);
-    }
-
-    #[test]
-    fn other_to_other() {
-        assert_eq!(length_conversion(1.0, Kilometer, Inch), 39370.07874015748);
-        assert_eq!(length_conversion(3.0, Kilometer, Mile), 1.8641182099494205);
-        assert_eq!(length_conversion(4.0, Foot, Yard), 1.3333333333333335);
-        assert_eq!(length_conversion(2.0, Inch, Mile), 3.156573502181019e-5);
-        assert_eq!(length_conversion(2.0, Centimeter, Millimeter), 20.0);
-        assert_eq!(
-            length_conversion(2.0, Centimeter, Yard),
-            0.021872265966754158
-        );
-        assert_eq!(length_conversion(4.0, Yard, Kilometer), 0.0036576);
-        assert_eq!(length_conversion(3.0, Foot, Inch), 36.00000000000001);
-        assert_eq!(length_conversion(4.0, Mile, Kilometer), 6.43736);
-        assert_eq!(length_conversion(2.0, Mile, Inch), 126719.68503937007);
-        assert_eq!(length_conversion(3.0, Millimeter, Centimeter), 0.3);
-        assert_eq!(
-            length_conversion(3.0, Millimeter, Inch),
-            0.11811023622047245
-        );
-    }
-
     #[test]
     fn zero_to_zero() {
         let units = vec![
@@ -122,7 +82,7 @@ mod length_conversion_tests {
 
     #[test]
     fn length_of_one_meter() {
-        let map = HashMap::from([
+        let meter_in_different_units = HashMap::from([
             (Millimeter, 1000f64),
             (Centimeter, 100f64),
             (Kilometer, 0.001f64),
@@ -131,9 +91,14 @@ mod length_conversion_tests {
             (Yard, 1.0936132983377078f64),
             (Mile, 0.0006213727366498068f64),
         ]);
-
-        for (k, v) in map {
-            assert_eq!(length_conversion(1f64, Meter, k), v);
+        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
+                );
+            }
         }
     }
 }