Wrap full evaluator pipeline into evaluator() function

src/eval.rs

@@ -5,6 +5,8 @@ pub mod differentiate;
 pub mod simplify;
 pub mod canonicalise;
 
+use crate::expression::Expression;
+
 pub use normalise::*;
 pub use const_fold::*;
 pub use compose::*;
@@ -31,3 +33,14 @@ impl std::fmt::Display for Error {
 		})
 	}
 }
+
+pub fn evaluator(var: char)
+				 -> impl Evaluator<Expr = Expression, Error = Error> {
+	crate::pipeline!(
+		Normaliser::new(),
+		Differentiator::new(var),
+		ConstFolder::new(),
+		Simplifier::new(),
+		ConstFolder::new(),
+		Canonicaliser::new())
+}