Parses infix expressions.

Signed-off-by: jmug <u.g.a.mariano@gmail.com>

pkg/ast/ast.go

@@ -131,7 +131,7 @@ func (il *IntegerLiteral) String() string {
 }
 
 type PrefixExpression struct {
-	Token    token.Token
+	Token    token.Token // The operator token
 	Operator string
 	Right    Expression
 }
@@ -143,3 +143,18 @@ func (pe *PrefixExpression) TokenLiteral() string {
 func (pe *PrefixExpression) String() string {
 	return "(" + pe.Operator + pe.Right.String() + ")"
 }
+
+type InfixExpression struct {
+	Token    token.Token // The operator token
+	Operator string
+	Left     Expression
+	Right    Expression
+}
+
+func (ie *InfixExpression) expressionNode() {}
+func (ie *InfixExpression) TokenLiteral() string {
+	return ie.Token.Literal
+}
+func (ie *InfixExpression) String() string {
+	return "(" + ie.Left.String() + " " + ie.Operator + " " + ie.Right.String() + ")"
+}