Disallow several temperatures in input

src/conversions.rs

@@ -62,7 +62,7 @@ fn get_conversion(unit: NonMetric) -> Conversion {
 		NonMetric::Fahrenheit => Conversion {
 			offset: 32.0,
 			from: 9.0,
-			to: MetricQuantity { amount: 5.0, unit: Metric::Celcius },
+			to: MetricQuantity { amount: 5.0, unit: Metric::Celsius },
 		},
 		// Area
 		NonMetric::SquareInch => Conversion {
@@ -122,14 +122,14 @@ mod test {
 			unit: NonMetric::Fahrenheit,
 		}), MetricQuantity {
 			amount: -40.0,
-			unit: Metric::Celcius,
+			unit: Metric::Celsius,
 		});
 		assert_eq!(convert(NonMetricQuantity {
 			amount: 32.0,
 			unit: NonMetric::Fahrenheit,
 		}), MetricQuantity {
 			amount: 0.0,
-			unit: Metric::Celcius,
+			unit: Metric::Celsius,
 		});
 	}
 

src/format.rs

@@ -83,7 +83,7 @@ fn prefixed_unit(quantity: MetricQuantity) -> PrefixedUnit {
 				return PrefixedUnit(1.0, "g");
 			}
 		}
-		Metric::Celcius => PrefixedUnit(1.0, "°C"),
+		Metric::Celsius => PrefixedUnit(1.0, "°C"),
 		Metric::SquareMetre => {
 			if absolute >= 1000.0 * 1000.0 {
 				return PrefixedUnit(1000.0 * 1000.0, "km²");
@@ -132,7 +132,7 @@ mod test {
 
 		assert_eq!("1 000 °C", &format(MetricQuantity {
 			amount: 1_000.0,
-			unit: Metric::Celcius,
+			unit: Metric::Celsius,
 		}));
 	}
 
@@ -259,18 +259,18 @@ mod test {
 	}
 
 	#[test]
-	fn celcius() {
+	fn celsius() {
 		assert_eq!(PrefixedUnit(1.0, "°C"), prefixed_unit(MetricQuantity {
 			amount: 0.0001,
-			unit: Metric::Celcius,
+			unit: Metric::Celsius,
 		}));
 		assert_eq!(PrefixedUnit(1.0, "°C"), prefixed_unit(MetricQuantity {
 			amount: -1.0,
-			unit: Metric::Celcius,
+			unit: Metric::Celsius,
 		}));
 		assert_eq!(PrefixedUnit(1.0, "°C"), prefixed_unit(MetricQuantity {
 			amount: 1_000.0,
-			unit: Metric::Celcius,
+			unit: Metric::Celsius,
 		}));
 	}
 

src/lib.rs

@@ -6,7 +6,7 @@ mod units;
 use conversions::convert;
 use format::format;
 use parse::{parse, ParseError};
-use units::{MetricQuantity, NonMetric};
+use units::{Metric, MetricQuantity, NonMetric};
 
 pub fn run(input: &str) -> Result<String, String> {
 	let non_metric = match parse(input) {
@@ -32,7 +32,8 @@ pub fn run(input: &str) -> Result<String, String> {
 	let metric: Vec<MetricQuantity> = non_metric.clone().into_iter().map(convert).collect();
 
 	// Make sure the results of the conversions can be summed together
-	// This is the case if the units after conversion are the same
+	// This is the case if the units after conversion are the same and
+	// they are not temperature units (i.e. degrees Celsius)
 	let mut metric_unit = None;
 	for index in 0..metric.len() {
 		match metric_unit {
@@ -48,6 +49,9 @@ pub fn run(input: &str) -> Result<String, String> {
 			}
 		}
 	}
+	if metric.len() > 1 && metric_unit == Some(Metric::Celsius) {
+		return Err("Cannot sum together temperatures".to_string());
+	}
 
 	let amount = metric.into_iter().map(|quantity| { quantity.amount }).sum();
 
@@ -92,6 +96,7 @@ mod test {
 		assert_eq!(run("1"), Err("Expected a unit".to_string()));
 		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()));
+		assert_eq!(run("0 °F 0 °F"), Err("Cannot sum together temperatures".to_string()));
 	}
 
 	#[test]

src/units.rs

@@ -2,7 +2,7 @@
 pub enum Metric {
 	Metre,
 	Gram,
-	Celcius,
+	Celsius,
 	SquareMetre,
 }