feat: no constructors for expressions and statements for saccharine

pkg/saccharine/expression.go

@@ -1,7 +1,7 @@
 package saccharine
 
 type Expression interface {
-	isExpression()
+	expression()
 }
 
 /** ------------------------------------------------------------------------- */
@@ -25,25 +25,7 @@ type Clause struct {
 	Returns    Expression
 }
 
-func (Abstraction) isExpression() {}
-func (Application) isExpression() {}
-func (Atom) isExpression()        {}
-func (Clause) isExpression()      {}
-
-/** ------------------------------------------------------------------------- */
-
-func NewAbstraction(parameter []string, body Expression) *Abstraction {
-	return &Abstraction{Parameters: parameter, Body: body}
-}
-
-func NewApplication(abstraction Expression, arguments []Expression) *Application {
-	return &Application{Abstraction: abstraction, Arguments: arguments}
-}
-
-func NewAtom(name string) *Atom {
-	return &Atom{Name: name}
-}
-
-func NewClause(statements []Statement, returns Expression) *Clause {
-	return &Clause{Statements: statements, Returns: returns}
-}
+func (Abstraction) expression() {}
+func (Application) expression() {}
+func (Atom) expression()        {}
+func (Clause) expression()      {}