Base visitor class for AST traversal. More...

#include <visitor.hpp>

Inheritance diagram for by::visitor:

Public Member Functions
	visitor (nbool isReturnable)

void	setReturnable (nbool isReturnable)

nbool	isReturnable () const

virtual void	visit (const visitInfo &i, node &me)

virtual nbool	onVisit (const visitInfo &i, node &me, nbool alreadyVisited)

virtual void	onLeave (const visitInfo &i, node &me, nbool alreadyVisited)

virtual void	onTraverse (const visitInfo &i, node &me)

virtual void	onTraverse (const visitInfo &i, asExpr &a)

virtual void	onTraverse (const visitInfo &i, assignExpr &a)

virtual void	onTraverse (const visitInfo &i, blockExpr &b)

virtual void	onTraverse (const visitInfo &i, defVarExpr &d)

virtual void	onTraverse (const visitInfo &i, FBOExpr &f)

virtual void	onTraverse (const visitInfo &i, getExpr &e)

virtual void	onTraverse (const visitInfo &i, retExpr &b)

virtual void	onTraverse (const visitInfo &i, evalExpr &e)

virtual void	onTraverse (evalExpr &e, node &subject)

virtual void	onTraverse (const visitInfo &i, func &f)

virtual void	onTraverse (const visitInfo &i, frame &f)

virtual void	onTraverse (const visitInfo &i, forExpr &f)

virtual void	onTraverse (const visitInfo &i, retStateExpr &r)

virtual void	onTraverse (const visitInfo &i, ifExpr &f)

virtual void	onTraverse (const visitInfo &i, whileExpr &w)

virtual void	onTraverse (const visitInfo &i, defArrayExpr &d)

virtual void	onTraverse (const visitInfo &i, defNestedFuncExpr &e)

virtual void	onTraverse (const visitInfo &i, genericOrigin &g)

virtual void	onTraverse (const visitInfo &i, obj &o)

Public Member Functions inherited from by::tworker< void, node >
	tworker (const errReport &rpt)

errReport &	getReport ()

const errReport &	getReport () const BY_CONST_FUNC(getReport()) me &setReport(errReport &rpt)

me &	setFlag (nint newFlag)

me &	addFlag (nint flag)

me &	delFlag (nint clear)

nbool	isFlag (nint flag) const

nint	getFlag () const

me &	setTask (const node &root)

me &	setTask (const node *it) BY_SIDE_FUNC(it

node *	getTask ()

const node *	getTask () const BY_CONST_FUNC(getTask()) virtual void rel()

void	work ()

const area &	getArea () const BY_CONST_FUNC(_getArea()) nbool isOk() const

Protected Member Functions
void	_onWork () override

void	_prepare () override
	Protected virtual method for preparation before starting the work.

Protected Member Functions inherited from by::tworker< void, node >
void	_report (baseErr *e)

virtual void	_onEndWork ()
	Protected virtual method called after the work is completed.

area &	_getArea ()

void	_onEndErrReport (const errReport &rpt) const

Additional Inherited Members
Public Types inherited from by::tworker< void, node >
enum	logFlag

Public Attributes inherited from by::tworker< void, node >
me setTask	it

me setTask *	this

Detailed Description

Base visitor class for AST traversal.

Since byeol focuses on AST, visitor is used frequently. visitor is actively utilized to separate the traversal method from the actions taken when visiting node during traversal.

Traversal

Always follows preorder traversal. Changing to postorder traversal is not possible. visit() consists of 3 stages:

Visit the currently found node (onVisit())
Traverse next child nodes (onTraverse())
Leave the currently found node (onLeave())

Downcasting Through accept

visitor has many virtual functions that represent visits to many concrete types like onVisit(T&). On the other hand, when searching in onTraverse, the node type is mainly used because it uses the tbicontainable interface through node's subs(). So somewhere the node type must be downcast to concrete types like nInt or defNestedFuncExpr. For this purpose, node's virtual function accept() is called. See the example:

void defNestedFuncExpr::accept(const visitInfo& i, visitor& v) {
    v.visit(i, *this); // calls visitor::visit(const visitInfo&, defNestedFuncExpr&)
}

When the virtual function accept() is called, it reversely calls visitor's visit() as a concrete type through *this. For this, all node-derived classes participating in visitation must override the virtual function accept(), and the VISIT macro is used to make this process easier. You will often see declarations like this:

class _nout pod: public node {
    BY(CLASS(pod, node), VISIT()) // <---
 
public:

If a node-derived class does not override accept(), onTraverse(node&) is used instead, which is sufficient for those cases.

Duplicate Visit Elimination

AST sometimes has mutual references between nodes. In this case, traversing without any exception handling revisits already visited nodes and enters an infinite loop. visitor owns a map called _visited. Through this, when visit() is called, it determines if it's an already visited node and provides exception handling. This visit history information is reset right before visitor starts visiting each time. If you want to enable revisiting, change the value with setReturnable(true).

Member Function Documentation

◆ _onWork()

void by::visitor::_onWork ( )

overrideprotectedvirtual

Implements by::tworker< void, node >.

◆ _prepare()

void by::visitor::_prepare ( )

overrideprotectedvirtual

Protected virtual method for preparation before starting the work.

This hook allows derived classes to perform any necessary setup or initialization before _onWork() is invoked.

Reimplemented from by::tworker< void, node >.

◆ setReturnable()

void by::visitor::setReturnable ( nbool isReturnable )

if you set the visitor as returnable, nodes you have already been visited, will be visited again if it's refered by different nodes. in default, this value is false.

The documentation for this class was generated from the following file:

/home/runner/work/byeol/byeol/module/core/worker/visitor/visitor.hpp

Public Member Functions

Protected Member Functions

Additional Inherited Members