Added unit conversion prototype

src/parser/mod.rs

@@ -13,7 +13,6 @@ use crate::parser::treeify::treeify;
 use crate::parser::find_subs::find_subs;
 
 use crate::quantity::Quantity;
-use crate::quantity::Unit;
 
 use crate::tokens::Token;
 

src/quantity/quantity.rs

@@ -82,6 +82,13 @@ impl Quantity {
 		});
 	}
 
+	pub fn from_scalar(s: Scalar) -> Quantity {
+		return Quantity{
+			v: s,
+			u: Unit::new()
+		};
+	}
+
 	pub fn insert_unit(&mut self, ui: BaseUnit, pi: Scalar) { self.u.insert(ui, pi) }
 	pub fn set_unit(&mut self, u: Unit) { self.u = u; }
 
@@ -96,6 +103,9 @@ impl Quantity {
 			"mol" => Some(BaseUnit::Mole),
 			"c" => Some(BaseUnit::Candela),
 			"ft" => Some(BaseUnit::Foot),
+			"mile" => Some(BaseUnit::Mile),
+			"hour" => Some(BaseUnit::Hour),
+			"min" => Some(BaseUnit::Minute),
 			_ => { None }
 		};
 
@@ -112,6 +122,17 @@ impl Quantity {
 		return None;
 	}
 
+	pub fn convert_to(self, other: Quantity) -> Option<Quantity> {
+		let fa = self.u.to_base_factor();
+		let fb = other.u.to_base_factor();
+		let r = self * fa / fb;
+
+		// If this didn't work, units are incompatible
+		if r.u != other.u { return None; };
+
+		return Some(r);
+	}
+
 }
 
 

src/quantity/unit.rs

@@ -21,30 +21,59 @@ pub enum BaseUnit {
 	Candela,
 
 	Foot,
+	Mile,
+	Minute,
+	Hour
 }
 
 impl BaseUnit {
-	pub fn is_base(&self) -> bool {
-		match self {
-			BaseUnit::Second
-			| BaseUnit::Meter
-			| BaseUnit::Kilogram
-			| BaseUnit::Ampere
-			| BaseUnit::Kelvin
-			| BaseUnit::Mole
-			| BaseUnit::Candela
-			=> true,
-
-			_ => false
-		}
-	}
-
 	pub fn to_base(&self) -> Option<Quantity> {
 		match self {
+
+			// Returns the unit we need to multiply by to get a base
+			// unit, or `None` if this is already a base unit.
+			//
+			// Example:
+			// 1 foot  = 0.3048 m,
+			// so 1 ft * (0.3084 m / ft) will give meters.
+			//
+			// The units here MUST be in terms of base units.
+			// If they aren't, things will break.
 			BaseUnit::Foot => Some(Quantity {
 				v: Scalar::new_float_from_string("0.3048").unwrap(),
-				u: Unit::from_array(&[(BaseUnit::Meter, Scalar::new_rational(1f64).unwrap())])
+				u: Unit::from_array(&[
+					(BaseUnit::Meter, Scalar::new_rational(1f64).unwrap()),
+					(BaseUnit::Foot, Scalar::new_rational(-1f64).unwrap())
+				])
 			}),
+
+			BaseUnit::Mile => Some(Quantity {
+				v: Scalar::new_float_from_string("1609").unwrap(),
+				u: Unit::from_array(&[
+					(BaseUnit::Meter, Scalar::new_rational(1f64).unwrap()),
+					(BaseUnit::Mile, Scalar::new_rational(-1f64).unwrap())
+				])
+			}),
+
+
+			BaseUnit::Minute => Some(Quantity {
+				v: Scalar::new_rational_from_string("60").unwrap(),
+				u: Unit::from_array(&[
+					(BaseUnit::Second, Scalar::new_rational(1f64).unwrap()),
+					(BaseUnit::Minute, Scalar::new_rational(-1f64).unwrap())
+				])
+			}),
+
+
+			BaseUnit::Hour => Some(Quantity {
+				v: Scalar::new_rational_from_string("3600").unwrap(),
+				u: Unit::from_array(&[
+					(BaseUnit::Second, Scalar::new_rational(1f64).unwrap()),
+					(BaseUnit::Hour, Scalar::new_rational(-1f64).unwrap())
+				])
+			}),
+
+			// Only base units should be missing a conversion factor.
 			_ => None
 		}
 	}
@@ -88,6 +117,9 @@ impl ToString for Unit {
 				BaseUnit::Candela => "c",
 
 				BaseUnit::Foot => "ft",
+				BaseUnit::Mile => "mile",
+				BaseUnit::Hour => "hour",
+				BaseUnit::Minute => "min",
 			};
 
 			if *p == Scalar::new_rational(1f64).unwrap() {
@@ -158,6 +190,19 @@ impl Unit {
 		};
 		return u;
 	}
+
+	pub fn to_base_factor(&self) -> Quantity {
+		let mut q = Quantity::new_rational(1f64).unwrap();
+
+		for (u, p) in self.val.iter() {
+			let b = u.to_base();
+			if b.is_some() {
+				q *= b.unwrap().pow(Quantity::from_scalar(p.clone()));
+			}
+		}
+
+		return q;
+	}
 }
 
 

src/tokens/operator.rs

@@ -13,6 +13,7 @@ use crate::quantity::Quantity;
 #[repr(usize)]
 pub enum Operator {
 	ModuloLong = 0, // Mod invoked with "mod"
+	UnitConvert,
 	Subtract,
 	Add,
 	Divide,
@@ -99,6 +100,14 @@ impl Operator {
 				);
 			},
 
+			Operator::UnitConvert => {
+				return format!(
+					"{} to {}",
+					self.add_parens_to_arg(&args[0]),
+					self.add_parens_to_arg(&args[1])
+				);
+			},
+
 			Operator::Modulo => {
 				return format!(
 					"{} % {}",
@@ -211,6 +220,7 @@ impl Operator {
 			"i*"     => {Some( Operator::ImplicitMultiply )},
 			"%"      => {Some( Operator::Modulo )},
 			"mod"    => {Some( Operator::ModuloLong )},
+			"to"    => {Some( Operator::UnitConvert )},
 			"^"|"**" => {Some( Operator::Power )},
 			"!"      => {Some( Operator::Factorial )},
 			"sqrt"|"rt"|"√" => {Some( Operator::Sqrt )},
@@ -327,6 +337,7 @@ impl Operator {
 			| Operator::Modulo
 			| Operator::Power
 			| Operator::ModuloLong
+			| Operator::UnitConvert
 			=> { Token::Operator(self, args) },
 		}
 	}
@@ -420,6 +431,23 @@ impl Operator{
 				} else { panic!(); }
 			},
 
+			Operator::UnitConvert
+			=> {
+				if args.len() != 2 {panic!()};
+				let a = args[0].as_number();
+				let b = args[1].as_number();
+
+				if let Token::Number(va) = a {
+					if let Token::Number(vb) = b {
+						let n = va.convert_to(vb);
+						if n.is_none() {
+							return Err(EvalError::IncompatibleUnit);
+						}
+						return Ok(Token::Number(n.unwrap()));
+					} else { panic!(); }
+				} else { panic!(); }
+			},
+
 			Operator::Power => {
 				if args.len() != 2 {panic!()};
 				let a = args[0].as_number();