Add support for degrees Fahrenheit

src/conversions.rs

@@ -2,12 +2,13 @@ use crate::units::{Metric, MetricQuantity, NonMetric, NonMetricQuantity};
 
 pub fn convert(from: NonMetricQuantity) -> MetricQuantity {
 	let conversion = get_conversion(from.unit);
-	let amount = from.amount * conversion.to.amount / conversion.from;
+	let amount = (from.amount - conversion.offset) * conversion.to.amount / conversion.from;
 	let unit = conversion.to.unit;
 	MetricQuantity { amount, unit }
 }
 
 struct Conversion {
+	offset: f64,
 	from: f64,
 	to: MetricQuantity,
 }
@@ -22,34 +23,47 @@ fn get_conversion(unit: NonMetric) -> Conversion {
 	match unit {
 		// Length
 		NonMetric::Inch => Conversion {
+			offset: 0.0,
 			from: inch_from,
 			to: MetricQuantity { amount: inch_to, unit: Metric::Metre },
 		},
 		NonMetric::Foot => Conversion {
+			offset: 0.0,
 			from: inch_from,
 			to: MetricQuantity { amount: 12.0 * inch_to, unit: Metric::Metre },
 		},
 		NonMetric::Yard => Conversion {
+			offset: 0.0,
 			from: inch_from,
 			to: MetricQuantity { amount: 3.0 * 12.0 * inch_to, unit: Metric::Metre },
 		},
 		NonMetric::Mile => Conversion {
+			offset: 0.0,
 			from: inch_from,
 			to: MetricQuantity { amount: 1760.0 * 3.0 * 12.0 * inch_to, unit: Metric::Metre },
 		},
 		// Weight
 		NonMetric::Ounce => Conversion {
+			offset: 0.0,
 			from: 16.0 * pound_from,
 			to: MetricQuantity { amount: pound_to, unit: Metric::Gram },
 		},
 		NonMetric::Pound => Conversion {
+			offset: 0.0,
 			from: pound_from,
 			to: MetricQuantity { amount: pound_to, unit: Metric::Gram },
 		},
 		NonMetric::Stone => Conversion {
+			offset: 0.0,
 			from: pound_from,
 			to: MetricQuantity { amount: 14.0 * pound_to, unit: Metric::Gram },
 		},
+		// Temperature
+		NonMetric::Fahrenheit => Conversion {
+			offset: 32.0,
+			from: 9.0,
+			to: MetricQuantity { amount: 5.0, unit: Metric::Celcius },
+		},
 	}
 }
 
@@ -80,6 +94,24 @@ mod test {
 		run_tests(&tests, Metric::Gram);
 	}
 
+	#[test]
+	fn temperature() {
+		assert_eq!(convert(NonMetricQuantity {
+			amount: -40.0,
+			unit: NonMetric::Fahrenheit,
+		}), MetricQuantity {
+			amount: -40.0,
+			unit: Metric::Celcius,
+		});
+		assert_eq!(convert(NonMetricQuantity {
+			amount: 32.0,
+			unit: NonMetric::Fahrenheit,
+		}), MetricQuantity {
+			amount: 0.0,
+			unit: Metric::Celcius,
+		});
+	}
+
 	fn run_tests(tests: &[Test], unit: Metric) {
 		for test in tests {
 			let from = NonMetricQuantity {

src/format.rs

@@ -1,66 +1,89 @@
 use crate::units::{Metric, MetricQuantity};
 
 pub fn format(quantity: MetricQuantity) -> String {
-	let (amount, prefix) = si_prefix(quantity.amount);
-	let unit = abbreviation(quantity.unit);
-
-	format!("{amount} {prefix}{unit}")
+	let PrefixedUnit(multiplier, unit) = prefixed_unit(quantity);
+	let amount = quantity.amount / multiplier;
+	let amount = format_number(amount);
+	format!("{amount} {unit}")
 }
 
-#[derive(Clone, Copy)]
-struct SiPrefix {
-	prefix: &'static str,
-	size: f64,
-}
+fn format_number(number: f64) -> String {
+	let sign = if number < 0.0 { "-" } else { "" };
+	let number = number.abs();
 
-const SI_PREFIXES: [SiPrefix; 16] = [
-	SiPrefix { prefix: "z", size: 0.000_000_000_000_000_000_001 },
-	SiPrefix { prefix: "a", size: 0.000_000_000_000_000_001 },
-	SiPrefix { prefix: "f", size: 0.000_000_000_000_001 },
-	SiPrefix { prefix: "p", size: 0.000_000_000_001 },
-	SiPrefix { prefix: "n", size: 0.000_000_001 },
-	SiPrefix { prefix: "µ", size: 0.000_001 },
-	SiPrefix { prefix: "m", size: 0.001 },
-	SiPrefix { prefix: "c", size: 0.01 }, // Included for cm
-	SiPrefix { prefix: "", size: 1.0 },
-	SiPrefix { prefix: "k", size: 1_000.0 },
-	SiPrefix { prefix: "M", size: 1_000_000.0 },
-	SiPrefix { prefix: "G", size: 1_000_000_000.0 },
-	SiPrefix { prefix: "T", size: 1_000_000_000_000.0 },
-	SiPrefix { prefix: "P", size: 1_000_000_000_000_000.0 },
-	SiPrefix { prefix: "E", size: 1_000_000_000_000_000_000.0 },
-	SiPrefix { prefix: "Z", size: 1_000_000_000_000_000_000_000.0 },
-	// Yotta and above cannot be represented exactly as a f64
-];
+	// Lower the number of decimal digits as the number grows, to try
+	// to maintain four significant figures
+	let precision = if number < 1.0 {
+		4
+	} else if number < 10.0 {
+		3
+	} else if number < 100.0 {
+		2
+	} else if number < 1000.0 {
+		1
+	} else {
+		0
+	};
 
-fn si_prefix(amount: f64) -> (f64, &'static str) {
-	let absolute = amount.abs();
-	if absolute < SI_PREFIXES[0].size {
-		let prefix = SI_PREFIXES[0];
-		return (amount / prefix.size, prefix.prefix);
-	}
-	if absolute >= SI_PREFIXES[SI_PREFIXES.len() - 1].size {
-		let prefix = SI_PREFIXES[SI_PREFIXES.len() - 1];
-		return (amount / prefix.size, prefix.prefix);
-	}
+	// Split number into integer and decimal parts for further processing
+	let formatted = format!("{number:.precision$}");
+	let mut formatted = formatted.split('.');
+	let integer = formatted.next().expect("f64 formatted with .precision$ must have a part before '.'");
+	let decimal = if precision > 0 {
+		formatted.next().expect("f64 formatted with .precision$ must have a part after '.' if precision > 0")
+	} else {
+		""
+	};
 
-	// Find the correct prefix SI_PREFIX[index] such that:
-	//  SI_PREFIXES[index].size ≤ absolute < SI_PREFIXES[index + 1].size
-	for index in 0..SI_PREFIXES.len() {
-		if SI_PREFIXES[index].size <= absolute &&
-		   absolute < SI_PREFIXES[index + 1].size {
-			let prefix = SI_PREFIXES[index];
-			return (amount / prefix.size, prefix.prefix);
+	// Group the integer part into groups of three, e.g. 1000 → 10 000
+	let mut grouped = String::new();
+	let mut group_length = 0;
+	for c in integer.chars().rev() {
+		if group_length == 3 {
+			grouped.push(' ');
+			group_length = 0;
 		}
+		grouped.push(c);
+		group_length += 1;
 	}
+	let grouped: String = grouped.chars().rev().collect();
 
-	unreachable!();
+	// Remove trailing zeroes
+	let decimal = decimal.trim_end_matches('0');
+
+	if decimal.len() == 0 {
+		format!("{sign}{grouped}")
+	} else {
+		format!("{sign}{grouped}.{decimal}")
+	}
 }
 
-fn abbreviation(unit: Metric) -> &'static str {
-	match unit {
-		Metric::Metre => "m",
-		Metric::Gram => "g",
+#[derive(Debug, PartialEq)]
+struct PrefixedUnit(f64, &'static str);
+
+fn prefixed_unit(quantity: MetricQuantity) -> PrefixedUnit {
+	let absolute = quantity.amount.abs();
+
+	match quantity.unit {
+		Metric::Metre => {
+			if absolute >= 1000.0 {
+				return PrefixedUnit(1000.0, "km");
+			} else if absolute >= 1.0 {
+				return PrefixedUnit(1.0, "m");
+			} else if absolute >= 0.01 {
+				return PrefixedUnit(0.01, "cm");
+			} else {
+				return PrefixedUnit(0.001, "mm");
+			}
+		}
+		Metric::Gram => {
+			if absolute >= 1000.0 {
+				return PrefixedUnit(1000.0, "kg");
+			} else {
+				return PrefixedUnit(1.0, "g");
+			}
+		}
+		Metric::Celcius => PrefixedUnit(1.0, "°C"),
 	}
 }
 
@@ -70,47 +93,167 @@ mod test {
 
 	#[test]
 	fn quantities() {
-		assert_eq!("1 m", &format(MetricQuantity {
-			amount: 1.0,
+		assert_eq!("0.1 mm", &format(MetricQuantity {
+			amount: 0.000_1,
 			unit: Metric::Metre,
 		}));
-		assert_eq!("5 kg", &format(MetricQuantity {
-			amount: 5_000.0,
+		assert_eq!("-1 m", &format(MetricQuantity {
+			amount: -1.0,
+			unit: Metric::Metre,
+		}));
+		assert_eq!("1.5 m", &format(MetricQuantity {
+			amount: 1.5,
+			unit: Metric::Metre,
+		}));
+		assert_eq!("1 000 km", &format(MetricQuantity {
+			amount: 1_000_000.0,
+			unit: Metric::Metre,
+		}));
+
+		assert_eq!("-5 g", &format(MetricQuantity {
+			amount: -5.0,
 			unit: Metric::Gram,
 		}));
-		assert_eq!("25.5 cm", &format(MetricQuantity {
-			amount: 0.255,
-			unit: Metric::Metre,
+		assert_eq!("3.2 kg", &format(MetricQuantity {
+			amount: 3_200.0,
+			unit: Metric::Gram,
+		}));
+
+		assert_eq!("1 000 °C", &format(MetricQuantity {
+			amount: 1_000.0,
+			unit: Metric::Celcius,
 		}));
 	}
 
 	#[test]
-	fn prefixes() {
-		assert_eq!(si_prefix(0.000_000_000_000_000_000_0005), (0.5, "z"));
-		assert_eq!(si_prefix(0.000_000_000_000_000_000_001), (1.0, "z"));
-		assert_eq!(si_prefix(0.000_000_000_000_000_000_01), (10.0, "z"));
-		assert_eq!(si_prefix(0.000_000_000_000_000_00_01), (100.0, "z"));
-		assert_eq!(si_prefix(0.000_000_000_000_000_001), (1.0, "a"));
-		assert_eq!(si_prefix(0.000_000_000_000_001), (1.0, "f"));
-		assert_eq!(si_prefix(0.000_000_000_001), (1.0, "p"));
-		assert_eq!(si_prefix(0.000_000_001), (1.0, "n"));
-		assert_eq!(si_prefix(0.000_001), (1.0, "µ"));
-		assert_eq!(si_prefix(0.001), (1.0, "m"));
-		assert_eq!(si_prefix(0.01), (1.0, "c"));
-		assert_eq!(si_prefix(1.0), (1.0, ""));
-		assert_eq!(si_prefix(1_000.0), (1.0, "k"));
-		assert_eq!(si_prefix(1_000_000.0), (1.0, "M"));
-		assert_eq!(si_prefix(1_000_000_000.0), (1.0, "G"));
-		assert_eq!(si_prefix(1_000_000_000_000.0), (1.0, "T"));
-		assert_eq!(si_prefix(1_000_000_000_000_000.0), (1.0, "P"));
-		assert_eq!(si_prefix(1_000_000_000_000_000_000.0), (1.0, "E"));
-		assert_eq!(si_prefix(10_000_000_000_000_000_000.0), (10.0, "E"));
-		assert_eq!(si_prefix(100_000_000_000_000_000_000.0), (100.0, "E"));
-		assert_eq!(si_prefix(1_000_000_000_000_000_000_000.0), (1.0, "Z"));
-		assert_eq!(si_prefix(2_000_000_000_000_000_000_000.0), (2.0, "Z"));
+	fn numbers() {
+		assert_eq!(&format_number(0.0001), "0.0001");
+		assert_eq!(&format_number(0.001), "0.001");
+		assert_eq!(&format_number(0.01), "0.01");
+		assert_eq!(&format_number(0.1), "0.1");
+		assert_eq!(&format_number(1.0), "1");
+		assert_eq!(&format_number(10.0), "10");
+		assert_eq!(&format_number(100.0), "100");
+		assert_eq!(&format_number(1_000.0), "1 000");
+		assert_eq!(&format_number(10_000.0), "10 000");
+		assert_eq!(&format_number(100_000.0), "100 000");
+		assert_eq!(&format_number(1_000_000.0), "1 000 000");
 
-		assert_eq!(si_prefix(-0.000_000_000_000_000_000_0005), (-0.5, "z"));
-		assert_eq!(si_prefix(-0.5), (-50.0, "c"));
-		assert_eq!(si_prefix(-2_000_000_000_000_000_000_000.0), (-2.0, "Z"));
+		assert_eq!(&format_number(0.00001), "0");
+		assert_eq!(&format_number(1.0001), "1");
+		assert_eq!(&format_number(1.001), "1.001");
+		assert_eq!(&format_number(10.001), "10");
+		assert_eq!(&format_number(10.01), "10.01");
+		assert_eq!(&format_number(100.01), "100");
+		assert_eq!(&format_number(100.1), "100.1");
+		assert_eq!(&format_number(1_000.1), "1 000");
+
+		assert_eq!(&format_number(-1.0), "-1");
+		assert_eq!(&format_number(-100.0), "-100");
+		assert_eq!(&format_number(-1000.0), "-1 000");
+	}
+
+	#[test]
+	fn units() {
+		assert_eq!(PrefixedUnit(0.001, "mm"), prefixed_unit(MetricQuantity {
+			amount: 0.0001,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(0.001, "mm"), prefixed_unit(MetricQuantity {
+			amount: 0.001,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(0.01, "cm"), prefixed_unit(MetricQuantity {
+			amount: 0.01,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(0.01, "cm"), prefixed_unit(MetricQuantity {
+			amount: 0.1,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "m"), prefixed_unit(MetricQuantity {
+			amount: 1.0,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "m"), prefixed_unit(MetricQuantity {
+			amount: 10.0,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "m"), prefixed_unit(MetricQuantity {
+			amount: 100.0,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(1000.0, "km"), prefixed_unit(MetricQuantity {
+			amount: 1000.0,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(1000.0, "km"), prefixed_unit(MetricQuantity {
+			amount: 10_000.0,
+			unit: Metric::Metre,
+		}));
+
+		assert_eq!(PrefixedUnit(0.001, "mm"), prefixed_unit(MetricQuantity {
+			amount: -0.001,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(0.01, "cm"), prefixed_unit(MetricQuantity {
+			amount: -0.01,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "m"), prefixed_unit(MetricQuantity {
+			amount: -1.0,
+			unit: Metric::Metre,
+		}));
+		assert_eq!(PrefixedUnit(1000.0, "km"), prefixed_unit(MetricQuantity {
+			amount: -1000.0,
+			unit: Metric::Metre,
+		}));
+
+		assert_eq!(PrefixedUnit(1.0, "g"), prefixed_unit(MetricQuantity {
+			amount: 0.1,
+			unit: Metric::Gram,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "g"), prefixed_unit(MetricQuantity {
+			amount: 1.0,
+			unit: Metric::Gram,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "g"), prefixed_unit(MetricQuantity {
+			amount: 10.0,
+			unit: Metric::Gram,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "g"), prefixed_unit(MetricQuantity {
+			amount: 100.0,
+			unit: Metric::Gram,
+		}));
+		assert_eq!(PrefixedUnit(1000.0, "kg"), prefixed_unit(MetricQuantity {
+			amount: 1000.0,
+			unit: Metric::Gram,
+		}));
+		assert_eq!(PrefixedUnit(1000.0, "kg"), prefixed_unit(MetricQuantity {
+			amount: 10_1000.0,
+			unit: Metric::Gram,
+		}));
+
+		assert_eq!(PrefixedUnit(1.0, "g"), prefixed_unit(MetricQuantity {
+			amount: -1.0,
+			unit: Metric::Gram,
+		}));
+		assert_eq!(PrefixedUnit(1000.0, "kg"), prefixed_unit(MetricQuantity {
+			amount: -1000.0,
+			unit: Metric::Gram,
+		}));
+
+		assert_eq!(PrefixedUnit(1.0, "°C"), prefixed_unit(MetricQuantity {
+			amount: 0.0001,
+			unit: Metric::Celcius,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "°C"), prefixed_unit(MetricQuantity {
+			amount: -1.0,
+			unit: Metric::Celcius,
+		}));
+		assert_eq!(PrefixedUnit(1.0, "°C"), prefixed_unit(MetricQuantity {
+			amount: 1_000.0,
+			unit: Metric::Celcius,
+		}));
 	}
 }

src/lib.rs

@@ -70,6 +70,8 @@ fn unit_to_name(unit: NonMetric) -> &'static str {
 		NonMetric::Ounce => "ounces",
 		NonMetric::Pound => "pounds",
 		NonMetric::Stone => "stones",
+		// Temperature
+		NonMetric::Fahrenheit => "degrees Fahrenheit",
 	}
 }
 
@@ -86,4 +88,21 @@ mod test {
 		assert_eq!(run(""), Err("Expected quantity or quantities to convert".to_string()));
 		assert_eq!(run("6 ft 1 lbs"), Err("Incompatible units: feet, pounds".to_string()));
 	}
+
+	#[test]
+	fn conversions() {
+		// Length
+		assert_eq!(run("1 in"), Ok("2.54 cm".to_string()));
+		assert_eq!(run("1 ft"), Ok("30.48 cm".to_string()));
+		assert_eq!(run("1 yard"), Ok("91.44 cm".to_string()));
+		assert_eq!(run("1 mile"), Ok("1.609 km".to_string()));
+		// Weight
+		assert_eq!(run("1 oz"), Ok("28.35 g".to_string()));
+		assert_eq!(run("1 lb"), Ok("453.6 g".to_string()));
+		assert_eq!(run("1 st"), Ok("6.35 kg".to_string()));
+		// Temperature
+		assert_eq!(run("-40 °F"), Ok("-40 °C".to_string()));
+		assert_eq!(run("0 °F"), Ok("-17.78 °C".to_string()));
+		assert_eq!(run("32 °F"), Ok("0 °C".to_string()));
+	}
 }

src/parse.rs

@@ -21,12 +21,7 @@ pub fn parse(input: &str) -> Result<Vec<NonMetricQuantity>, ParseError> {
 	for token in tokenize(input) {
 		match (&state, token) {
 			(Expect::Number, Token::Number(number)) => {
-				let number = match number.trim().parse() {
-					Ok(number) => number,
-					Err(_) => {
-						return Err(ParseError::NotValidNumber(number));
-					}
-				};
+				let number = parse_number(number)?;
 				amount = Some(number);
 				state = Expect::Unit;
 			}
@@ -37,12 +32,7 @@ pub fn parse(input: &str) -> Result<Vec<NonMetricQuantity>, ParseError> {
 				unreachable!("token stream can't contain two numbers in a row");
 			}
 			(Expect::Unit, Token::Unit(unit)) => {
-				let unit = match parse_unit(&unit) {
-					Some(unit) => unit,
-					None => {
-						return Err(ParseError::UnknownUnit(unit));
-					}
-				};
+				let unit = parse_unit(unit)?;
 				let quantity = NonMetricQuantity {
 					amount: amount.take().expect("must have read a number to be in this state"),
 					unit: unit,
@@ -63,46 +53,55 @@ pub fn parse(input: &str) -> Result<Vec<NonMetricQuantity>, ParseError> {
 	Ok(quantities)
 }
 
-fn parse_unit(input: &str) -> Option<NonMetric> {
-	match input {
+fn parse_number(input: String) -> Result<f64, ParseError> {
+	let no_whitespace: String = input.chars().filter(|c| !c.is_whitespace()).collect();
+	no_whitespace.parse().or_else(|_| Err(ParseError::NotValidNumber(input)))
+}
+
+fn parse_unit(input: String) -> Result<NonMetric, ParseError> {
+	match input.as_str() {
 		// Length
-		"inch" => Some(NonMetric::Inch),
-		"inches" => Some(NonMetric::Inch),
-		"in" => Some(NonMetric::Inch),
-		"\"" => Some(NonMetric::Inch),
-		"″" => Some(NonMetric::Inch),
+		"inch" => Ok(NonMetric::Inch),
+		"inches" => Ok(NonMetric::Inch),
+		"in" => Ok(NonMetric::Inch),
+		"\"" => Ok(NonMetric::Inch),
+		"″" => Ok(NonMetric::Inch),
 
-		"foot" => Some(NonMetric::Foot),
-		"feet" => Some(NonMetric::Foot),
-		"ft" => Some(NonMetric::Foot),
-		"'" => Some(NonMetric::Foot),
-		"′" => Some(NonMetric::Foot),
+		"foot" => Ok(NonMetric::Foot),
+		"feet" => Ok(NonMetric::Foot),
+		"ft" => Ok(NonMetric::Foot),
+		"'" => Ok(NonMetric::Foot),
+		"′" => Ok(NonMetric::Foot),
 
-		"yard" => Some(NonMetric::Yard),
-		"yards" => Some(NonMetric::Yard),
-		"yd" => Some(NonMetric::Yard),
+		"yard" => Ok(NonMetric::Yard),
+		"yards" => Ok(NonMetric::Yard),
+		"yd" => Ok(NonMetric::Yard),
 
-		"mile" => Some(NonMetric::Mile),
-		"miles" => Some(NonMetric::Mile),
-		"mi" => Some(NonMetric::Mile),
-		"m" => Some(NonMetric::Mile),
+		"mile" => Ok(NonMetric::Mile),
+		"miles" => Ok(NonMetric::Mile),
+		"mi" => Ok(NonMetric::Mile),
+		"m" => Ok(NonMetric::Mile),
 
 		// Weight
-		"ounce" => Some(NonMetric::Ounce),
-		"ounces" => Some(NonMetric::Ounce),
-		"oz" => Some(NonMetric::Ounce),
+		"ounce" => Ok(NonMetric::Ounce),
+		"ounces" => Ok(NonMetric::Ounce),
+		"oz" => Ok(NonMetric::Ounce),
 
-		"pound" => Some(NonMetric::Pound),
-		"pounds" => Some(NonMetric::Pound),
-		"lb" => Some(NonMetric::Pound),
-		"lbs" => Some(NonMetric::Pound),
-		"#" => Some(NonMetric::Pound),
+		"pound" => Ok(NonMetric::Pound),
+		"pounds" => Ok(NonMetric::Pound),
+		"lb" => Ok(NonMetric::Pound),
+		"lbs" => Ok(NonMetric::Pound),
+		"#" => Ok(NonMetric::Pound),
 
-		"stone" => Some(NonMetric::Stone),
-		"stones" => Some(NonMetric::Stone),
-		"st" => Some(NonMetric::Stone),
+		"stone" => Ok(NonMetric::Stone),
+		"stones" => Ok(NonMetric::Stone),
+		"st" => Ok(NonMetric::Stone),
 
-		_ => None,
+		// Temperature
+		"°F" => Ok(NonMetric::Fahrenheit),
+		"F" => Ok(NonMetric::Fahrenheit),
+
+		_ => Err(ParseError::UnknownUnit(input)),
 	}
 }
 
@@ -187,6 +186,9 @@ mod test {
 			NonMetricQuantity { amount: 5.0, unit: NonMetric::Foot },
 			NonMetricQuantity { amount: 8.0, unit: NonMetric::Inch },
 		]));
+		assert_eq!(parse("20 000 lbs"), Ok(vec![
+			NonMetricQuantity { amount: 20_000.0, unit: NonMetric::Pound },
+		]));
 
 		assert_eq!(parse("12.0."), Err(ParseError::NotValidNumber("12.0.".to_string())));
 		assert_eq!(parse("ft"), Err(ParseError::UnexpectedUnit("ft".to_string())));
@@ -194,47 +196,62 @@ mod test {
 		assert_eq!(parse("12"), Err(ParseError::ExpectedUnit));
 	}
 
+	#[test]
+	fn numbers() {
+		assert_eq!(parse_number("".to_string()), Err(ParseError::NotValidNumber("".to_string())));
+		assert_eq!(parse_number("1".to_string()), Ok(1.0));
+		assert_eq!(parse_number("1.0".to_string()), Ok(1.0));
+		assert_eq!(parse_number("0.1".to_string()), Ok(0.1));
+		assert_eq!(parse_number("0.1.".to_string()), Err(ParseError::NotValidNumber("0.1.".to_string())));
+		assert_eq!(parse_number("-10".to_string()), Ok(-10.0));
+		assert_eq!(parse_number("10\t00\u{1680}000".to_string()), Ok(10_00_000.0));
+	}
+
 	#[test]
 	fn units() {
 		// Length
-		assert_eq!(parse_unit("inch"), Some(NonMetric::Inch));
-		assert_eq!(parse_unit("inches"), Some(NonMetric::Inch));
-		assert_eq!(parse_unit("in"), Some(NonMetric::Inch));
-		assert_eq!(parse_unit("\""), Some(NonMetric::Inch));
-		assert_eq!(parse_unit("″"), Some(NonMetric::Inch));
+		assert_eq!(parse_unit("inch".to_string()), Ok(NonMetric::Inch));
+		assert_eq!(parse_unit("inches".to_string()), Ok(NonMetric::Inch));
+		assert_eq!(parse_unit("in".to_string()), Ok(NonMetric::Inch));
+		assert_eq!(parse_unit("\"".to_string()), Ok(NonMetric::Inch));
+		assert_eq!(parse_unit("″".to_string()), Ok(NonMetric::Inch));
 
-		assert_eq!(parse_unit("foot"), Some(NonMetric::Foot));
-		assert_eq!(parse_unit("feet"), Some(NonMetric::Foot));
-		assert_eq!(parse_unit("ft"), Some(NonMetric::Foot));
-		assert_eq!(parse_unit("'"), Some(NonMetric::Foot));
-		assert_eq!(parse_unit("′"), Some(NonMetric::Foot));
+		assert_eq!(parse_unit("foot".to_string()), Ok(NonMetric::Foot));
+		assert_eq!(parse_unit("feet".to_string()), Ok(NonMetric::Foot));
+		assert_eq!(parse_unit("ft".to_string()), Ok(NonMetric::Foot));
+		assert_eq!(parse_unit("'".to_string()), Ok(NonMetric::Foot));
+		assert_eq!(parse_unit("′".to_string()), Ok(NonMetric::Foot));
 
-		assert_eq!(parse_unit("yard"), Some(NonMetric::Yard));
-		assert_eq!(parse_unit("yards"), Some(NonMetric::Yard));
-		assert_eq!(parse_unit("yd"), Some(NonMetric::Yard));
+		assert_eq!(parse_unit("yard".to_string()), Ok(NonMetric::Yard));
+		assert_eq!(parse_unit("yards".to_string()), Ok(NonMetric::Yard));
+		assert_eq!(parse_unit("yd".to_string()), Ok(NonMetric::Yard));
 
-		assert_eq!(parse_unit("mile"), Some(NonMetric::Mile));
-		assert_eq!(parse_unit("miles"), Some(NonMetric::Mile));
-		assert_eq!(parse_unit("mi"), Some(NonMetric::Mile));
-		assert_eq!(parse_unit("m"), Some(NonMetric::Mile));
+		assert_eq!(parse_unit("mile".to_string()), Ok(NonMetric::Mile));
+		assert_eq!(parse_unit("miles".to_string()), Ok(NonMetric::Mile));
+		assert_eq!(parse_unit("mi".to_string()), Ok(NonMetric::Mile));
+		assert_eq!(parse_unit("m".to_string()), Ok(NonMetric::Mile));
 
 		// Weight
-		assert_eq!(parse_unit("ounce"), Some(NonMetric::Ounce));
-		assert_eq!(parse_unit("ounces"), Some(NonMetric::Ounce));
-		assert_eq!(parse_unit("oz"), Some(NonMetric::Ounce));
+		assert_eq!(parse_unit("ounce".to_string()), Ok(NonMetric::Ounce));
+		assert_eq!(parse_unit("ounces".to_string()), Ok(NonMetric::Ounce));
+		assert_eq!(parse_unit("oz".to_string()), Ok(NonMetric::Ounce));
 
-		assert_eq!(parse_unit("pound"), Some(NonMetric::Pound));
-		assert_eq!(parse_unit("pounds"), Some(NonMetric::Pound));
-		assert_eq!(parse_unit("lb"), Some(NonMetric::Pound));
-		assert_eq!(parse_unit("lbs"), Some(NonMetric::Pound));
-		assert_eq!(parse_unit("#"), Some(NonMetric::Pound));
+		assert_eq!(parse_unit("pound".to_string()), Ok(NonMetric::Pound));
+		assert_eq!(parse_unit("pounds".to_string()), Ok(NonMetric::Pound));
+		assert_eq!(parse_unit("lb".to_string()), Ok(NonMetric::Pound));
+		assert_eq!(parse_unit("lbs".to_string()), Ok(NonMetric::Pound));
+		assert_eq!(parse_unit("#".to_string()), Ok(NonMetric::Pound));
 
-		assert_eq!(parse_unit("stone"), Some(NonMetric::Stone));
-		assert_eq!(parse_unit("stones"), Some(NonMetric::Stone));
-		assert_eq!(parse_unit("st"), Some(NonMetric::Stone));
+		assert_eq!(parse_unit("stone".to_string()), Ok(NonMetric::Stone));
+		assert_eq!(parse_unit("stones".to_string()), Ok(NonMetric::Stone));
+		assert_eq!(parse_unit("st".to_string()), Ok(NonMetric::Stone));
+
+		// Temperature
+		assert_eq!(parse_unit("°F".to_string()), Ok(NonMetric::Fahrenheit));
+		assert_eq!(parse_unit("F".to_string()), Ok(NonMetric::Fahrenheit));
 
 		// Unknown unit
-		assert_eq!(parse_unit("hutenosa"), None);
+		assert_eq!(parse_unit("hutenosa".to_string()), Err(ParseError::UnknownUnit("hutenosa".to_string())));
 	}
 
 	#[test]
@@ -243,6 +260,8 @@ mod test {
 		assert_eq!(tokenize("10"), vec![Token::Number("10".to_string())]);
 		assert_eq!(tokenize("  10  "), vec![Token::Number("10".to_string())]);
 		assert_eq!(tokenize("10 000"), vec![Token::Number("10 000".to_string())]);
+		assert_eq!(tokenize("10\t000"), vec![Token::Number("10\t000".to_string())]);
+		assert_eq!(tokenize("10\u{1680}000"), vec![Token::Number("10\u{1680}000".to_string())]);
 		assert_eq!(tokenize("10.0.1"), vec![Token::Number("10.0.1".to_string())]);
 		assert_eq!(tokenize("ft"), vec![Token::Unit("ft".to_string())]);
 		assert_eq!(

src/units.rs

@@ -2,6 +2,7 @@
 pub enum Metric {
 	Metre,
 	Gram,
+	Celcius,
 }
 
 #[derive(Clone, Copy, Debug, PartialEq)]
@@ -15,9 +16,11 @@ pub enum NonMetric {
 	Ounce,
 	Pound,
 	Stone,
+	// Temperature
+	Fahrenheit,
 }
 
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub struct MetricQuantity {
 	pub amount: f64,
 	pub unit: Metric,