feat: reducer, but doesn`t work

pkg/parser/parser.go

@@ -15,15 +15,15 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 	}
 
 	switch token.Type {
-	case tokenizer.TokenAtom:
-		return lambda.NewAtom(token.Value), nil
+	case tokenizer.TokenVariable:
+		return lambda.NewVariable(token.Value), nil
 	case tokenizer.TokenDot:
 		return nil, fmt.Errorf("Token '.' found without a corresponding slash (column %d).", token.Index)
 	case tokenizer.TokenSlash:
 		atom, atom_err := i.Next()
 		if atom_err != nil {
 			return nil, fmt.Errorf("Could not find parameter of function: %w", atom_err)
-		} else if atom.Type != tokenizer.TokenAtom {
+		} else if atom.Type != tokenizer.TokenVariable {
 			return nil, fmt.Errorf("Expected function parameter, got '%v' (column %d).", atom.Value, atom.Index)
 		}
 
@@ -39,7 +39,7 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 			return nil, fmt.Errorf("Could not parse function body: %w", body_err)
 		}
 
-		return lambda.NewFunction(atom.Value, body), nil
+		return lambda.NewAbstraction(atom.Value, body), nil
 	case tokenizer.TokenOpenParen:
 		fn, fn_err := ParseExpression(i)
 		if fn_err != nil {
@@ -58,7 +58,7 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 			return nil, fmt.Errorf("Expected call terminating parenthesis, got '%v' (column %v).", close.Value, close.Index)
 		}
 
-		return lambda.NewCall(fn, arg), nil
+		return lambda.NewApplication(fn, arg), nil
 	case tokenizer.TokenCloseParen:
 		return nil, fmt.Errorf("Token ')' found without a corresponding openning parenthesis (column %d).", token.Index)
 	default: