Add support for imperial gallons

src/conversions.rs

@@ -20,6 +20,9 @@ fn get_conversion(unit: NonMetric) -> Conversion {
 	let pound_from = 100_000.0;
 	let pound_to = 45359237.0;
 
+	let imperial_gallon_from = 100_000.0;
+	let imperial_gallon_to = 454609.0;
+
 	match unit {
 		// Length
 		NonMetric::Inch => Conversion {
@@ -96,6 +99,12 @@ fn get_conversion(unit: NonMetric) -> Conversion {
 			from: inch_from * inch_from * inch_from,
 			to: MetricQuantity { amount: 12.0 * inch_to * 12.0 * inch_to * 12.0 * inch_to, unit: Metric::CubicMetre },
 		},
+		// Fluid volume
+		NonMetric::ImperialGallon => Conversion {
+			offset: 0.0,
+			from: imperial_gallon_from,
+			to: MetricQuantity { amount: imperial_gallon_to, unit: Metric::Litre },
+		},
 	}
 }
 
@@ -164,6 +173,14 @@ mod test {
 		run_tests(&tests, Metric::CubicMetre);
 	}
 
+	#[test]
+	fn fluid_volume() {
+		let tests = [
+			Test(NonMetric::ImperialGallon, 4.54609),
+		];
+		run_tests(&tests, Metric::Litre);
+	}
+
 	fn run_tests(tests: &[Test], unit: Metric) {
 		for test in tests {
 			let from = NonMetricQuantity {

src/format.rs

@@ -106,6 +106,17 @@ fn prefixed_unit(quantity: MetricQuantity) -> PrefixedUnit {
 				return PrefixedUnit(0.001 * 0.001 * 0.001, "mm³");
 			}
 		}
+		Metric::Litre => {
+			if absolute >= 1.0 {
+				return PrefixedUnit(1.0, "l");
+			} else if absolute >= 0.1 {
+				return PrefixedUnit(0.1, "dl");
+			} else if absolute >= 0.01 {
+				return PrefixedUnit(0.01, "cl");
+			} else {
+				return PrefixedUnit(0.001, "ml");
+			}
+		}
 	}
 }
 
@@ -392,4 +403,32 @@ mod test {
 			unit: Metric::CubicMetre,
 		}));
 	}
+
+	#[test]
+	fn litre() {
+		assert_eq!(PrefixedUnit(0.001, "ml"), prefixed_unit(MetricQuantity {
+			amount: 0.000_1,
+			unit: Metric::Litre,
+		}));
+		assert_eq!(PrefixedUnit(0.001, "ml"), prefixed_unit(MetricQuantity {
+			amount: 0.001,
+			unit: Metric::Litre,
+		}));
+		assert_eq!(PrefixedUnit(0.01, "cl"), prefixed_unit(MetricQuantity {
+			amount: 0.01,
+			unit: Metric::Litre,
+		}));
+		assert_eq!(PrefixedUnit(0.1, "dl"), prefixed_unit(MetricQuantity {
+			amount: 0.1,
+			unit: Metric::Litre,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "l"), prefixed_unit(MetricQuantity {
+			amount: 1.0,
+			unit: Metric::Litre,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "l"), prefixed_unit(MetricQuantity {
+			amount: 10.0,
+			unit: Metric::Litre,
+		}));
+	}
 }

src/lib.rs

@@ -84,6 +84,8 @@ fn unit_to_name(unit: NonMetric) -> &'static str {
 		// Volume
 		NonMetric::CubicInch => "cubic inches",
 		NonMetric::CubicFoot => "cubic feet",
+		// Fluid volume
+		NonMetric::ImperialGallon => "imperial gallons",
 	}
 }
 
@@ -125,5 +127,7 @@ mod test {
 		// Volume
 		assert_eq!(run("1 in³"), Ok("16.39 cm³".to_string()));
 		assert_eq!(run("1 ft³"), Ok("28 317 cm³".to_string()));
+		// Fluid volume
+		assert_eq!(run("1 imp gal"), Ok("4.546 l".to_string()));
 	}
 }

src/parse.rs

@@ -185,6 +185,11 @@ fn parse_unit(input: String) -> Result<NonMetric, ParseError> {
 		"feet^3" => Ok(NonMetric::CubicFoot),
 		"ft^3" => Ok(NonMetric::CubicFoot),
 
+		// Fluid volume
+		"imperial gallon" => Ok(NonMetric::ImperialGallon),
+		"imperial gallons" => Ok(NonMetric::ImperialGallon),
+		"imp gal" => Ok(NonMetric::ImperialGallon),
+
 		_ => Err(ParseError::UnknownUnit(input)),
 	}
 }
@@ -419,6 +424,11 @@ mod test {
 		assert_eq!(parse_unit("feet^3".to_string()), Ok(NonMetric::CubicFoot));
 		assert_eq!(parse_unit("ft^3".to_string()), Ok(NonMetric::CubicFoot));
 
+		// Fluid volume
+		assert_eq!(parse_unit("imperial gallon".to_string()), Ok(NonMetric::ImperialGallon));
+		assert_eq!(parse_unit("imperial gallons".to_string()), Ok(NonMetric::ImperialGallon));
+		assert_eq!(parse_unit("imp gal".to_string()), Ok(NonMetric::ImperialGallon));
+
 		// Unknown unit
 		assert_eq!(parse_unit("hutenosa".to_string()), Err(ParseError::UnknownUnit("hutenosa".to_string())));
 	}

src/units.rs

@@ -5,6 +5,7 @@ pub enum Metric {
 	Celsius,
 	SquareMetre,
 	CubicMetre,
+	Litre,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -28,6 +29,8 @@ pub enum NonMetric {
 	// Volume
 	CubicInch,
 	CubicFoot,
+	// Fluid volume
+	ImperialGallon,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq)]