fix: parameters converted in opposite order

pkg/convert/saccharine_to_lambda.go

@@ -0,0 +1,52 @@
+package convert
+
+import (
+	"git.maximhutz.com/max/lambda/pkg/lambda"
+	"git.maximhutz.com/max/lambda/pkg/saccharine/ast"
+)
+
+type compileVisitor struct{}
+
+func (v compileVisitor) VisitAtom(n *ast.Atom) lambda.Expression {
+	return lambda.NewVariable(n.Name)
+}
+
+func (v compileVisitor) VisitAbstraction(n *ast.Abstraction) lambda.Expression {
+	result := ast.Visit(v, n.Body)
+
+	parameters := n.Parameters
+
+	// If the function has no parameters, it is a thunk. Lambda calculus still
+	// requires _some_ parameter exists, so generate one.
+	if len(parameters) == 0 {
+		freeVars := lambda.GetFreeVariables(result)
+		freshName := lambda.GenerateFreshName(freeVars)
+		parameters = append(parameters, freshName)
+	}
+
+	for i := len(parameters) - 1; i >= 0; i-- {
+		result = lambda.NewAbstraction(parameters[i], result)
+	}
+
+	return result
+}
+
+func (v compileVisitor) VisitApplication(n *ast.Application) lambda.Expression {
+	result := ast.Visit(v, n.Abstraction)
+
+	arguments := []lambda.Expression{}
+	for _, argument := range n.Arguments {
+		convertedArgument := ast.Visit(v, argument)
+		arguments = append(arguments, convertedArgument)
+	}
+
+	for _, argument := range arguments {
+		result = lambda.NewApplication(result, argument)
+	}
+
+	return result
+}
+
+func SaccharineToLambda(n ast.Expression) lambda.Expression {
+	return ast.Visit(&compileVisitor{}, n)
+}