waiig15/ast/ast.go

package ast

// Node is the interface implemented by every node in the AST.
type Node interface {
	// TokenLiteral returns the literal value of the token it's associated to.
	TokenLiteral() string
}

// Statement extends Node and is only a way to differentiate between expressions
// and statements.
type Statement interface {
	Node
	statementNode()
}

// Expression extends Node and is only a way to differentiate between
// expressions and statements.
type Expression interface {
	// Expression extends Node.
	Node
	expressionNode()
}

// Program represents the outer structure of the parser program.
type Program struct {
	Statements []Statement
}

// TokenLiteral returns the string contents of the first statement token, which
// can be an empty string if the program is empty.
func (p *Program) TokenLiteral() string {
	if len(p.Statements) > 0 {
		return p.Statements[0].TokenLiteral()
	}

	return ""
}