All nodes in a Loyc syntax tree share this base class. More...

Source file:

/Core/Loyc.Syntax/LNodes/LNode.cs

Inheritance diagram for Loyc.Syntax.LNode:

Remarks

All nodes in a Loyc syntax tree share this base class.

Loyc defines only three types of nodes: simple symbols, literals, and calls.

A IdNode is a simple identifier, such as a VariableName
A LiteralNode is a literal constant, such as 123 or "hello"
A CallNode encompasses all other kinds of nodes, such as normal function calls like f(x), generic specifications like f<x> (represented as #of(f, x)), braced blocks of statements (represented as <tt>{}(stmt1, stmt2, ...)), and so on. Also, parenthesized expressions are represented as a call with one argument and null as the Target.

This class provides access to all properties of all three types of nodes, in order to make this class easier to access from plain C#, and to avoid unnecessary downcasting in some cases.

Loyc nodes are always immutable, except for the 8-bit Style property which normally affects printing only.

Background information

EC# (enhanced C#) is intended to be the starting point of the Loyc (Language of your choice) project, which will be a family of programming languages that will share a common representation for the syntax tree and other compiler-related data structures.

Just as LLVM assembly has emerged as a nearly universal standard intermediate representation for back-ends, Loyc nodes are intended to be a universal intermediate representation for syntax trees, and Loyc will (eventually) include a generic set of tools for semantic analysis so that it provides a generic representation for front-ends.

EC#, then, will be the first language to use the Loyc syntax tree representation, known as the "Loyc tree" for short. Most syntax trees are very strongly typed, with separate data types for, say, variable declarations, binary operators, method calls, method declarations, unary operators, and so forth. Loyc, however, defines only three types of Nodes, and this one class provides access to all the parts of a node. There are several reasons for this design:

Simplicity. Many compilers have thousands of lines of code dedicated to the AST (abstract syntax tree) data structure itself, because each kind of AST node has its own class.
Serializability. Loyc nodes can always be serialized to a plain text "prefix tree" and deserialized back to objects, even by programs that are not designed to handle the language that the tree represents*. This makes it easy to visualize syntax trees or exchange them between programs.
Extensibility. Loyc nodes can represent any language imaginable, and they are suitable for embedded DSLs (domain-specific languages). Since nodes do not enforce a particular structure, they can be used in different ways than originally envisioned. For example, most languages only have "+" as a binary operator, that is, with two arguments. If Loyc had a separate class for each AST, there would probably be a PlusOperator class derived from BinaryOperator, or something, with properties "Left" and "Right". But since there is only one node class, a "+" operator with three arguments is always possible; this is denoted by #+(a, b, c) in EC# source code.

Currently, the only supported languages for plain-text Loyc trees are LES and EC# (either normal EC# or prefix-tree notation).

Loyc trees are comparable to LISP trees, except that "attributes" and position information are added to the tree, and the concept of a "list" is replaced with the concept of a "call", which I feel is a more intuitive notion in most programming languages that are not LISP.

Loyc's representation is both an blessing and a curse. The advantage is that Loyc nodes can be used for almost any purpose, perhaps even representing data instead of code in some cases. However, there is no guarantee that a given AST follows the structure prescribed by a particular programming language, unless a special validation step is performed after parsing. In this way, Loyc trees are similar to XML trees, only simpler.

Another major disadvantage is that it is more difficult to interpret a syntax tree correctly: you have to remember that a method definition has the structure #fn(return_type, name, args, body), so if "node" is a method definition then node.Args[2] represents the return type, for example. In contrast, most compilers have an AST class called MethodDefinition or something, that provides properties such as Name and ReturnType. Once EC# is developed, however, aliases could help avoid this problem by providing a more friendly veneer over the raw nodes.

For optimization purposes, the node class is a class hierarchy, but most users should only use this class and perhaps the three derived classes IdNode, LiteralNode and CallNode. Some users will also find it useful to use LNodeFactory for generating synthetic code snippets (bits of code that never existed in any source file), although you can also use the methods defined here in this class: Id(), Literal(), Call(), InParens().

Normal LNodes are "persistent" in the comp-sci sense, which means that a subtree can be shared among multiple syntax trees, and nodes do not know their own parents. This allows a single node to exist at multiple locations in a syntax tree. This makes manipulation of trees convenient, as there is no need to "detach" a node from one place, or duplicate it, before it can be inserted in another place. Immutable nodes can be safely re-used within different source files or multiple versions of one source file in an IDE's "intellisense" or "code completion" engine.

The reimplementation

This implementation has been redesigned (in Subversion, the last version based on the old design is revision 289.) The core concept is the same as described in my blog at http://loyc-etc.blogspot.ca/2013/04/the-loyc-tree-and-prefix-notation-in-ec.html except that the concept of a "Head" has mostly been eliminated, although you might see it occasionally because it still has a meaning. The "head" of a node refers either to the Name of a symbol, the Value of a literal, or the Target of a call (i.e. the name of the method being called, which could be an arbitrarily complex node). In the original implementation, it was also possible to have a complex head (a head that is itself a node) even when the node was not a call; this situation was used to represent an expression in parenthesis.

This didn't quite feel right, so I changed it. Now, only calls can be complex, and the head of a call (the method being called) is called the Target.

In the new version, there are explicitly three types of nodes: symbols, literals, and calls. There is no longer a Head property, instead there are three separate properties for the three kinds of heads, Name (a Symbol), Value (an Object), and Target (an LNode). Only call nodes have a Target, and only literal nodes have a Value (as an optimization, StdTriviaNode breaks this rule; it can only do this because it represents special attributes that are outside the normal syntax tree, such as comments). Symbol nodes have a Name, but I thought it would be useful for some call nodes to also have a Name, which is defined as the name of the Target if the Target is a symbol (if the Target is not a symbol, the Name must be blank.)

An expression in parenthesis is now represented by a call with a blank name (use IsParenthesizedExpr to detect this case; it is incorrect to test Name == $`` because a call with a non-symbol Target also has a blank name.)

The following differences in implementation have been made:

"Red" and "green" nodes have basically been eliminated, at least for now.
Nodes normally do not contain parent references anymore
Mutable nodes have been eliminated, for now.
There are now three standard subclasses, IdNode, LiteralNode and CallNode, and a node can no longer change between classes after it is created.
An empty Name is now allowed. A literal now has a blank name (instead of #literal) and a method that calls anything other than a simple symbol will also have a blank Name. Note: The Name property will still never return null.
As mentioned, an expression in parenthesis is represented differently.

The problems that motivated a redesign are described at http://loyc-etc.blogspot.ca/2013/05/redesigning-loyc-tree-code.html

One very common use of mutable nodes is building lists of statements, e.g. you might create an empty braced block or an empty loop and then add statements to the body of the block or loop. To do this without mutable nodes, create a mutable WList{LNode} instead and add statements there; once the list is finished, create the braced block or loop afterward. The new design stores arguments and attributes in VList{LNode} objects; you can instantly convert your WList to a VList by calling WListBase{LNode}.ToVList().

During the redesign I've decided on some small changes to the representation of certain expressions in EC#.

The '.' operator is now treated more like a normal binary operator; a.b.c is now represented #.(#.(a, b), c) rather than #.(a, b, c) mainly because it's easier that way, and because the second representation doesn't buy anything significant other than a need for special-casing.
int x = 0 will now be represented #var(int, x = 0) rather than #var(int, x(0)). I chose the latter representation initially because it is slightly more convenient, because you can always learn the name of the declared variable by calling var.Args[1].Name. However, I decided that it was more important for the syntax tree to be predictable, with obvious connections between normal and prefix notations. Since I decided that alias X = Y; was to be represented #alias(X = Y, #()), it made sense for the syntax tree of a variable declaration to also resemble its C# syntax. There's another small reason: C++ has both styles Foo x(y) and Foo x = y; if Loyc were to ever support C++, it would make sense to use #var(Foo, x(y)) and #var(Foo, x = y) for these two cases, and I believe C#'s variable declarations are semantically closer to the latter. (Note: another possibility was #var(int, x) = 0, but I decided this wasn't an improvement, it would just shift the pain around.)
An constructor argument list is required on all types using the #new operator, e.g. new int[] { x } must have an empty set of arguments on int[], i.e. #new(#of(#[],int)(), x); this rule makes the different kinds of new expressions easier to interpret by making them consistent with each other.
A missing syntax element is now represented by an empty symbol instead of the symbol #missing.
I've decided to adopt the "in-expression" generics syntax from Nemerle as an unambiguous alternative to angle brackets: List.[int] means List<int> and the printer will use this syntax in cases where angle brackets are ambiguous.
By popular demand, constructors will be written this(...) instead of new(...), since both D and Nemerle use the latter notation.
The \ and $ characters have been swapped; now denotes a symbol S, while $S now denotes a substitution.
The \ and $ characters have been swapped; now denotes a symbol S, while $S now denotes a substitution. Originally EC# was designed just as an extension of C#, so \ made sense as a substitution operator for string interpolation because it doesn't hurt backward compatibility: "Loaded '\(filename)' successfully". But now that my focus has shifted to multi-language interoperability, $ makes more sense, as it is used for string interpolation in at least five other languages and it makes sense to use the same character for both string substitution and code substitution.

Important properties

The main properties of a node are

Attrs: holds the attributes of the node, if any.
Name: the name of an IdNode, or the name of the IdNode that is acting as the Target of a CallNode.
Value: the value of a LiteralNode.
Target: the target of a CallNode. It represents a method, macro, or special identifier that is being called.
Args: holds the arguments to a CallNode, if any. Returns an empty list if the node does not have an argument list.
Range: indicates the source file that the node came from and location in that source file.
Style: an 8-bit flag value that is used as a hint to the node printer about how the node should be printed. For example, a hex literal like 0x10 has the NodeStyle.Alternate style to distinguish it from decimal literals such as 16. Custom display styles that do not fit in the Style property can be expressed with attributes.

The argument and attribute lists cannot be null, since they have type VList{Node} which is a struct.

LNode implements INegListSource{T}, so you can loop through all children of the node like this:

for (int i = node.Min; i &lt;= node.Max; i++) {
    LNode child = node[i];
}

You can also use foreach. The children are numbered like this:

if i is less than -1, node[i] refers to an attribute. Specifically, node[i] means node.Attrs[i + node.Attrs.Count + 1] in that case.
node[-1] refers to Target (but throws if there is no target)
Non-negative values are indexes of Args, e.g. node[i] means node.Args[i].

LNode also provides Select(child => result) and ReplaceRecursive(child => result) methods which allows you to transform all children (Atrrs, Target and Args). Currently there is no Where(child => bool) method because it is not possible to remove the Target of an LNode (you can still use standard LINQ Where(), of course, but the result is not an LNode).

Note

The argument and attribute lists should never contain null nodes. Any code that puts nulls in Args or Attrs is buggy. However, we can't ensure nulls are not placed into VList{T} since it's a general-purpose data type, not specialized for LNode. There is code to ensure nulls are not placed in Args and Attrs (NoNulls), but only in debug builds, since null-checking is fairly expensive.

Nested classes
class	DeepComparer
	An IEqualityComparer that compares nodes structurally. More...

struct	PushedPrinter
	Returned by PushPrinter(LNodePrinter). More...

Public static fields
static readonly EmptySourceFile	SyntheticSource = new EmptySourceFile("<Synthetic Code>")

static readonly IdNode	Missing = Id(CodeSymbols.Missing)

static readonly LNode	InParensTrivia = Id(CodeSymbols.TriviaInParens)

Properties
virtual SourceRange	Range `[get]`
	Returns the location and range in source code of this node. More...

ISourceFile	Source `[get]`
	Returns the source file (shortcut for `Range.Source`). More...

NodeStyle	Style `[get, set]`
	Indicates the preferred style to use when printing the node to a text string. More...

NodeStyle	BaseStyle `[get, set]`

virtual VList< LNode >	Attrs `[get]`
	Returns the attribute list for this node. More...

virtual bool	IsFrozen `[get]`
	Returns true if the node is immutable, and false if any part of it can be edited. Currently, mutable nodes are not implemented. More...

abstract LNodeKind	Kind `[get]`
	Returns the LNodeKind: Symbol, Literal, or Call. More...

bool	IsCall `[get]`

bool	IsId `[get]`

bool	IsLiteral `[get]`

abstract Symbol	Name `[get]`
	Returns the Symbol if IsId. If this node is a call (IsCall) and `Target.IsId` is true, this property returns `Target.Name`. In all other cases, the name is GSymbol.Empty. Shall not return null. More...

bool	HasSpecialName `[get]`
	Returns true if Name starts with '#'. More...

bool	HasValue `[get]`

abstract object	Value `[get]`
	Returns the value of a literal node, or NoValue.Value if this node is not a literal (IsLiteral is false). More...

abstract LNode	Target `[get]`
	Returns the target of a method call, or null if IsCall is false. The target can be a symbol with no name (GSymbol.Empty) to represent a parenthesized expression, if there is one argument. More...

abstract VList< LNode >	Args `[get]`
	Returns the argument list of this node. Always empty when `IsCall==false`. More...

static LNodePrinter	Printer `[get, set]`
	Gets or sets the default node printer on the current thread, which controls how nodes are serialized to text by default. More...

virtual object	TriviaValue `[get]`
	Gets the value of `Args[0].Value`, if Args[0] exists; otherwise, returns NoValue.Value. More...

bool	HasTokenValue `[get]`

int	ArgCount `[get]`

int	AttrCount `[get]`

bool	HasAttrs `[get]`

bool	IsTrivia `[get]`

int	Min `[get]`

virtual int	Max `[get]`

LNode	this[int index] `[get]`

int	Count `[get]`

Properties inherited from Loyc.IHasLocation
object	Location `[get]`

Properties inherited from Loyc.IHasValue< out T >
T	Value `[get]`

Public Member Functions
LNode	SetBaseStyle (NodeStyle s)

LNode	SetStyle (NodeStyle s)

virtual LNode	WithName (Symbol name)
	Creates a node with a new value for Name. More...

abstract LiteralNode	WithValue (object value)
	Creates a new literal node with a different Value than the current literal node. More...

virtual CallNode	WithTarget (LNode target)

virtual CallNode	WithTarget (Symbol name)

abstract CallNode	WithArgs (VList< LNode > args)
	Creates a Node with a new argument list. If this node is not a call, a new node is created using this node as its target. Otherwise, the existing argument list is replaced. More...

virtual CallNode	With (LNode target, VList< LNode > args)
	Creates a CallNode with the same attributes and Range, but a different target and argument list. If the current node is not a CallNode, it becomes one (the Range, Style and attributes of the current node are kept, but the Kind, Value, and Name are discarded.) More...

virtual CallNode	With (Symbol target, VList< LNode > args)
	Creates a CallNode with the same attributes and Range, but a different target and argument list. If the current node is not a CallNode, it becomes one (the Range, Style and attributes of the current node are kept, but the Kind, Value, and Name are discarded.) More...

CallNode	With (Symbol target, params LNode[] args)

abstract LNode	Clone ()
	Creates a copy of the node. Since nodes are immutable, there is little reason for an end-user to call this, but Clone() is used internally as a helper method by the WithXyz() methods. More...

LNode	WithRange (SourceRange range)

LNode	WithRange (int startIndex, int endIndex)

LNode	WithStyle (NodeStyle style)

virtual LNode	With (SourceRange range, NodeStyle style)

virtual LNode	WithoutAttrs ()

abstract LNode	WithAttrs (VList< LNode > attrs)

LNode	WithAttrs (params LNode[] attrs)

CallNode	WithArgs (params LNode[] args)

LNode	PlusAttr (LNode attr)

LNode	PlusAttrs (VList< LNode > attrs)

LNode	PlusAttrs (IEnumerable< LNode > attrs)

LNode	PlusAttrs (params LNode[] attrs)

LNode	PlusArg (LNode arg)

LNode	PlusArgs (VList< LNode > args)

LNode	PlusArgs (IEnumerable< LNode > args)

LNode	PlusArgs (params LNode[] args)

LNode	WithArgChanged (int index, LNode newValue)

LNode	WithAttrChanged (int index, LNode newValue)

abstract void	Call (LNodeVisitor visitor)

abstract void	Call (ILNodeVisitor visitor)

virtual string	Print (object mode=null, string indentString="\t", string lineSeparator="\n")

override string	ToString ()

abstract bool	Equals (LNode other, bool compareStyles)
	Compares two nodes for structural equality. Two green nodes are considered equal if they have the same name, the same value, the same arguments, and the same attributes. IsCall must be the same, but they need not have the same values of SourceWidth or IsFrozen. More...

bool	Equals (LNode other)

override bool	Equals (object other)

override int	GetHashCode ()
	Gets the hash code based on the structure of the tree. More...

bool	HasPAttrs ()

VList< LNode >	PAttrs ()

virtual bool	Calls (Symbol name, int argCount)

virtual bool	Calls (string name, int argCount)

virtual bool	Calls (Symbol name)

virtual bool	Calls (string name)

virtual bool	CallsMin (Symbol name, int argCount)

virtual bool	CallsMin (string name, int argCount)

virtual bool	HasSimpleHead ()
	Returns true if this is not a call, or if the call's Target is an Id or a Literal. More...

virtual bool	HasSimpleHeadWithoutPAttrs ()
	Returns true if this is not a call, or if the call's Target is an Id or a Literal, and the Target has only trivia attributes. More...

LNode	WithAttrs (Func< LNode, Maybe< LNode >> selector)

virtual LNode	WithArgs (Func< LNode, Maybe< LNode >> selector)

virtual bool	IsIdWithoutPAttrs ()

virtual bool	IsIdWithoutPAttrs (Symbol name)

virtual bool	IsIdNamed (Symbol name)

virtual bool	IsIdNamed (string name)

virtual bool	IsParenthesizedExpr ()

CallNode	WithSplicedArgs (int index, LNode from, Symbol listName)

CallNode	WithSplicedArgs (LNode from, Symbol listName)

LNode	WithSplicedAttrs (int index, LNode from, Symbol listName)

LNode	WithSplicedAttrs (LNode from, Symbol listName)

NestedEnumerable < DescendantsFrame, LNode >	Descendants (NodeScanMode mode=NodeScanMode.YieldAllChildren)

NestedEnumerable < DescendantsFrame, LNode >	DescendantsAndSelf ()

LNode	TryGet (int index, out bool fail)

IRange< LNode >	Slice (int start, int count=int.MaxValue)

IEnumerator< LNode >	GetEnumerator ()

abstract LNode	Select (Func< LNode, LNode > selector)
	Transforms the attributes, Target, and parameters of an LNode, returning another LNode of the same Kind. If the selector makes no changes, Select() returns `this`. More...

abstract LNode	ReplaceRecursive (Func< LNode, LNode > selector, bool replaceRoot=true)
	Performs a recursive find-and-replace operation, by attempting to replace each child (among Attrs, Target, Args) using the specified selector. This method can also be used for simple searching, by giving a selector that always returns null. More...

Static Public Member Functions
static IdNode	Id (Symbol name, LNode prototype)

static IdNode	Id (string name, LNode prototype)

static IdNode	Id (VList< LNode > attrs, Symbol name, LNode prototype)

static IdNode	Id (VList< LNode > attrs, string name, LNode prototype)

static LiteralNode	Literal (object value, LNode prototype)

static LiteralNode	Literal (VList< LNode > attrs, object value, LNode prototype)

static CallNode	Call (Symbol name, LNode prototype)

static CallNode	Call (LNode target, LNode prototype)

static CallNode	Call (Symbol name, VList< LNode > args, LNode prototype)

static CallNode	Call (LNode target, VList< LNode > args, LNode prototype)

static CallNode	Call (VList< LNode > attrs, Symbol name, VList< LNode > args, LNode prototype)

static CallNode	Call (VList< LNode > attrs, LNode target, VList< LNode > args, LNode prototype)

static CallNode	Trivia (Symbol name, object value, LNode prototype)

static LNode	InParens (LNode node)

static IdNode	Id (Symbol name, SourceRange range, NodeStyle style=NodeStyle.Default)

static IdNode	Id (string name, SourceRange range, NodeStyle style=NodeStyle.Default)

static IdNode	Id (VList< LNode > attrs, Symbol name, SourceRange range, NodeStyle style=NodeStyle.Default)

static IdNode	Id (VList< LNode > attrs, string name, SourceRange range, NodeStyle style=NodeStyle.Default)

static LiteralNode	Literal (object value, SourceRange range, NodeStyle style=NodeStyle.Default)

static LiteralNode	Literal (VList< LNode > attrs, object value, SourceRange range, NodeStyle style=NodeStyle.Default)

static CallNode	Call (Symbol name, SourceRange range, NodeStyle style=NodeStyle.Default)

static CallNode	Call (LNode target, SourceRange range, NodeStyle style=NodeStyle.Default)

static CallNode	Call (Symbol name, VList< LNode > args, SourceRange range, NodeStyle style=NodeStyle.Default)

static CallNode	Call (LNode target, VList< LNode > args, SourceRange range, NodeStyle style=NodeStyle.Default)

static CallNode	Call (VList< LNode > attrs, Symbol name, VList< LNode > args, SourceRange range, NodeStyle style=NodeStyle.Default)

static CallNode	Call (VList< LNode > attrs, LNode target, VList< LNode > args, SourceRange range, NodeStyle style=NodeStyle.Default)

static CallNode	Trivia (Symbol name, object value, SourceRange range, NodeStyle style=NodeStyle.Default)

static LNode	InParens (LNode node, SourceRange range)

static IdNode	Id (Symbol name, ISourceFile file=null, int position=-1, int width=-1)

static IdNode	Id (string name, ISourceFile file=null, int position=-1, int width=-1)

static IdNode	Id (VList< LNode > attrs, Symbol name, ISourceFile file=null, int position=-1, int width=-1)

static IdNode	Id (VList< LNode > attrs, string name, ISourceFile file=null, int position=-1, int width=-1)

static LiteralNode	Literal (object value, ISourceFile file=null, int position=-1, int width=-1, NodeStyle style=NodeStyle.Default)

static LiteralNode	Literal (VList< LNode > attrs, object value, ISourceFile file=null, int position=-1, int width=-1, NodeStyle style=NodeStyle.Default)

static CallNode	Call (Symbol name, ISourceFile file=null, int position=-1, int width=-1, NodeStyle style=NodeStyle.Default)

static CallNode	Call (LNode target, ISourceFile file=null, int position=-1, int width=-1, NodeStyle style=NodeStyle.Default)

static CallNode	Call (Symbol name, VList< LNode > args, ISourceFile file=null, int position=-1, int width=-1, NodeStyle style=NodeStyle.Default)

static CallNode	Call (LNode target, VList< LNode > args, ISourceFile file=null, int position=-1, int width=-1, NodeStyle style=NodeStyle.Default)

static CallNode	Call (VList< LNode > attrs, Symbol name, VList< LNode > args, ISourceFile file=null, int position=-1, int width=-1, NodeStyle style=NodeStyle.Default)

static CallNode	Call (VList< LNode > attrs, LNode target, VList< LNode > args, ISourceFile file=null, int position=-1, int width=-1, NodeStyle style=NodeStyle.Default)

static CallNode	Trivia (Symbol name, object value, ISourceFile file=null, int position=-1, int width=-1, NodeStyle style=NodeStyle.Default)

static LNode	InParens (LNode node, ISourceFile file=null, int position=-1, int width=-1)

static VList< LNode >	List ()

static VList< LNode >	List (LNode list_0)

static VList< LNode >	List (LNode list_0, LNode list_1)

static VList< LNode >	List (params LNode[] list)

static VList< LNode >	List (IEnumerable< LNode > list)

static VList< LNode >	List (VList< LNode > list)

static PushedPrinter	PushPrinter (LNodePrinter printer)
	Helps you change printers temporarily. Usage in C#: `using (LNode.PushPrinter(myPrinter)) { ... }` More...

static bool	Equals (LNode a, LNode b, bool compareStyles=false)

static bool	Equals (VList< LNode > a, VList< LNode > b, bool compareStyles=false)
	Compares two lists of nodes for structural equality. More...

static LNode	MergeLists (LNode node1, LNode node2, Symbol listName)
	Some CallNodes are used to represent lists. This method merges two nodes, forming or appending a list (see remarks). More...

static LNode	MergeBinary (LNode node1, LNode node2, Symbol binaryOpName)
	Combines two nodes using a binary operator or function. More...

Protected Member Functions
	LNode (LNode prototype)

	LNode (SourceRange range, NodeStyle style)

Static Protected Member Functions
static void	NoNulls (VList< LNode > list, string propName)

Protected fields
RangeAndStyle	RAS

Member Function Documentation

abstract LNode Loyc.Syntax.LNode.Clone ( )

pure virtual

Creates a copy of the node. Since nodes are immutable, there is little reason for an end-user to call this, but Clone() is used internally as a helper method by the WithXyz() methods.

Implements Loyc.ICloneable< out T >.

Implemented in Loyc.Syntax.CallNode, Loyc.Syntax.LiteralNode, and Loyc.Syntax.IdNode.

static bool Loyc.Syntax.LNode.Equals	(	VList< LNode >	a,
		VList< LNode >	b,
		bool	compareStyles = `false`
	)

inlinestatic

Compares two lists of nodes for structural equality.

Parameters

compareStyles Whether to compare values of Style

Position information is not compared.

abstract bool Loyc.Syntax.LNode.Equals	(	LNode	other,
		bool	compareStyles
	)

pure virtual

Compares two nodes for structural equality. Two green nodes are considered equal if they have the same name, the same value, the same arguments, and the same attributes. IsCall must be the same, but they need not have the same values of SourceWidth or IsFrozen.

Parameters

compareStyles Whether to compare values of Style

Position information (Range) is not compared.

Implemented in Loyc.Syntax.CallNode, Loyc.Syntax.LiteralNode, and Loyc.Syntax.IdNode.

override int Loyc.Syntax.LNode.GetHashCode ( )

inline

Gets the hash code based on the structure of the tree.

If the tree is large, less than the entire tree is scanned to produce the hashcode (in the absolute worst case, about 4000 nodes are examined, but usually it is less than 100).

References Loyc.Syntax.LNode.GetHashCode().

Referenced by Loyc.Syntax.LNode.GetHashCode().

virtual bool Loyc.Syntax.LNode.HasSimpleHead ( )

inlinevirtual

Returns true if this is not a call, or if the call's Target is an Id or a Literal.

Reimplemented in Loyc.Syntax.CallNode.

virtual bool Loyc.Syntax.LNode.HasSimpleHeadWithoutPAttrs ( )

inlinevirtual

Returns true if this is not a call, or if the call's Target is an Id or a Literal, and the Target has only trivia attributes.

Reimplemented in Loyc.Syntax.CallNode.

static LNode Loyc.Syntax.LNode.MergeBinary	(	LNode	node1,
		LNode	node2,
		Symbol	binaryOpName
	)

inlinestatic

Combines two nodes using a binary operator or function.

Parameters

node1	First node, list, or null.
node2	Second node, list, or null.
binaryOpName	Binary operator to use when the nodes are not null.

Returns: If either node1 or node2 is null, this method returns the other node (node1 ?? node2), otherwise the nodes are joined with the specified operator.

static LNode Loyc.Syntax.LNode.MergeLists	(	LNode	node1,
		LNode	node2,
		Symbol	listName
	)

inlinestatic

Some CallNodes are used to represent lists. This method merges two nodes, forming or appending a list (see remarks).

Parameters

node1	First node, list, or null.
node2	Second node, list, or null.
listName	The Name used to detect whether a node is a list (typically "#splice"). Any other name is considered a normal call, not a list. If this method creates a list from two non- lists, this parameter specifies the Name that the list will have.

Returns: The merged list.

The order of the data is retained (i.e. the data in node1 is inserted before the data in node2).

If either node1 or node2 is null, this method returns the other (node1 ?? node2).
If both node1 and node2 are lists, this method merges the list into a single list by appending node2's arguments at the end of node1. The attributes of node1 are kept and those of node2 are discarded.
If one of the nodes is a list and the other is not, the non-list is inserted into the list's Args.
If neither node is a list, a list is created with both nodes as its two Args.

See also: LNodeExt.WithSpliced

static PushedPrinter Loyc.Syntax.LNode.PushPrinter ( LNodePrinter printer )

inlinestatic

Helps you change printers temporarily. Usage in C#: using (LNode.PushPrinter(myPrinter)) { ... }

For example, to switch to the EC# printer, use using (LNode.PushPrinter(EcsNodePrinter.Printer)) { ... }. This changes the default printer. If you don't want to change the default printer, please invoke the printer directly:

var sb = new StringBuilder();

EcsNodePrinter.Printer(node, sb, MessageSink.Trace);

abstract LNode Loyc.Syntax.LNode.ReplaceRecursive	(	Func< LNode, LNode >	selector,
		bool	replaceRoot = `true`
	)

pure virtual

Performs a recursive find-and-replace operation, by attempting to replace each child (among Attrs, Target, Args) using the specified selector. This method can also be used for simple searching, by giving a selector that always returns null.

Parameters

selector	The selector is called for each descendant, and optionally the root node. If the selector returns a node, the new node replaces the node that was passed to `selector` and the children of the new node are ignored. If the selector returns null, children of the child are scanned recursively.
replaceRoot	Whether to call `selector(this)`.

Returns: The new node produced after all replacements have occurred.

If replaceFunc always returns null (or if replaceRoot is false and the root has no children), ReplaceRecursive returns this.

Implemented in Loyc.Syntax.CallNode, Loyc.Syntax.LiteralNode, and Loyc.Syntax.IdNode.

abstract LNode Loyc.Syntax.LNode.Select ( Func< LNode, LNode > selector )

pure virtual

Transforms the attributes, Target, and parameters of an LNode, returning another LNode of the same Kind. If the selector makes no changes, Select() returns this.

The selector is not allowed to return null.

Implemented in Loyc.Syntax.CallNode, Loyc.Syntax.LiteralNode, and Loyc.Syntax.IdNode.

virtual CallNode Loyc.Syntax.LNode.With	(	LNode	target,
		VList< LNode >	args
	)

inlinevirtual

Creates a CallNode with the same attributes and Range, but a different target and argument list. If the current node is not a CallNode, it becomes one (the Range, Style and attributes of the current node are kept, but the Kind, Value, and Name are discarded.)

virtual CallNode Loyc.Syntax.LNode.With	(	Symbol	target,
		VList< LNode >	args
	)

inlinevirtual

Creates a CallNode with the same attributes and Range, but a different target and argument list. If the current node is not a CallNode, it becomes one (the Range, Style and attributes of the current node are kept, but the Kind, Value, and Name are discarded.)

abstract CallNode Loyc.Syntax.LNode.WithArgs ( VList< LNode > args )

pure virtual

Creates a Node with a new argument list. If this node is not a call, a new node is created using this node as its target. Otherwise, the existing argument list is replaced.

Parameters

args	New argument list

Implemented in Loyc.Syntax.CallNode, Loyc.Syntax.LiteralNode, and Loyc.Syntax.IdNode.

virtual LNode Loyc.Syntax.LNode.WithName ( Symbol name )

inlinevirtual

Creates a node with a new value for Name.

If IsId, the Name is simply changed. If IsCall, this method returns the equivalent of WithTarget(Target.WithName(name)) (which may be optimized for the particular call type). If IsLiteral, the Kind changes to LNodeKind.Id in order to set the name.

Reimplemented in Loyc.Syntax.CallNode, and Loyc.Syntax.IdNode.

abstract LiteralNode Loyc.Syntax.LNode.WithValue ( object value )

pure virtual

Creates a new literal node with a different Value than the current literal node.

Exceptions

InvalidOperationException The node was not a literal already.

Implemented in Loyc.Syntax.CallNode, Loyc.Syntax.LiteralNode, and Loyc.Syntax.IdNode.

Property Documentation

abstract VList<LNode> Loyc.Syntax.LNode.Args

get

Returns the argument list of this node. Always empty when IsCall==false.

Depending on the Target, Args may represent an actual argument list, or it may represent some other kind of list. For example, if the target is "{}" then Args represents a list of statements in a braced block, and if the target is ">=" then Args represents the two arguments to the ">=" operator.

Referenced by Loyc.Syntax.LNodeExt.AsList(), Loyc.LLParserGenerator.CodeGenHelperBase.CallRule(), Loyc.LLParserGenerator.IntStreamCodeGenHelper.CodeToTerminalPred(), Loyc.Syntax.CallNode.Equals(), Loyc.Ecs.EcsValidators.KeyNameComponentOf(), Loyc.LLPG.Macros.LLLPG_parser(), Loyc.LLParserGenerator.CodeGenHelperBase.SetListInitializer(), and Loyc.Ecs.EcsValidators.SpaceStatementKind().

virtual VList<LNode> Loyc.Syntax.LNode.Attrs

get

Returns the attribute list for this node.

Referenced by Loyc.Syntax.IdNode.Equals(), Loyc.Syntax.LiteralNode.Equals(), Loyc.Syntax.CallNode.Equals(), and Loyc.Ecs.EcsValidators.IsPrintableTypeParam().

bool Loyc.Syntax.LNode.HasSpecialName

get

Returns true if Name starts with '#'.

Note that this property returns false for the empty identifier @``.

virtual bool Loyc.Syntax.LNode.IsFrozen

get

Returns true if the node is immutable, and false if any part of it can be edited. Currently, mutable nodes are not implemented.

Debugger-hidden until such time as mutable nodes actually exist.

abstract LNodeKind Loyc.Syntax.LNode.Kind

get

Returns the LNodeKind: Symbol, Literal, or Call.

Referenced by Loyc.Syntax.IdNode.Equals(), Loyc.Syntax.LiteralNode.Equals(), Loyc.Syntax.CallNode.Equals(), and Loyc.Syntax.LNodeExt.MatchesPattern().

abstract Symbol Loyc.Syntax.LNode.Name

get

Returns the Symbol if IsId. If this node is a call (IsCall) and Target.IsId is true, this property returns Target.Name. In all other cases, the name is GSymbol.Empty. Shall not return null.

Examples (using C#/LES syntax):

Expression   Kind    Name (blank if empty)
hello        Id      hello
#if         Id      #if
Foo(x, y)    Call    Foo
x += y       Call    +=
x.Foo(y)     Call    
5.0          Literal

Referenced by Loyc.LLParserGenerator.GeneralCodeGenHelper.CodeToTerminalPred(), and Loyc.Syntax.LNodeExt.MatchesPattern().

LNodePrinter Loyc.Syntax.LNode.Printer

staticgetset

Gets or sets the default node printer on the current thread, which controls how nodes are serialized to text by default.

The LES printer is the default, and will be used if you try to set this property to null.

virtual SourceRange Loyc.Syntax.LNode.Range

get

Returns the location and range in source code of this node.

A parser should record a sufficiently wide range for each parent node, such that all children are fully contained within the range. However, this is not an invariant; macros can splice together syntax trees from different source files or add synthetic nodes, so that the parent range does not necessarily include all child ranges. (In fact, in general it is impossible to ensure that parent ranges include child ranges because a parent can only specify a single source file, while children can come from several source files.)

ISourceFile Loyc.Syntax.LNode.Source

get

Returns the source file (shortcut for Range.Source).

NodeStyle Loyc.Syntax.LNode.Style

getset

Indicates the preferred style to use when printing the node to a text string.

The Style is an 8-bit value that acts as a hint to the node printer about how the node should be printed. Custom display styles that do not fit in the Style property can be expressed with special attributes that have a Name starting with "#trivia_". ("#trivia" attributes, which are also used to store comments in the syntax tree, are not printed like normal attributes and are normally ignored if the node printer does not specifically recognize them.)

Referenced by Loyc.Syntax.IdNode.Equals(), Loyc.Syntax.LiteralNode.Equals(), and Loyc.Syntax.CallNode.Equals().

abstract LNode Loyc.Syntax.LNode.Target

get

Returns the target of a method call, or null if IsCall is false. The target can be a symbol with no name (GSymbol.Empty) to represent a parenthesized expression, if there is one argument.

Referenced by Loyc.Syntax.CallNode.Equals(), Loyc.Ecs.EcsValidators.KeyNameComponentOf(), and Loyc.Syntax.LNodeExt.MatchesPattern().

virtual object Loyc.Syntax.LNode.TriviaValue

get

Gets the value of Args[0].Value, if Args[0] exists; otherwise, returns NoValue.Value.

"Trivia nodes" are used to efficiently represent the value of trivia and non-tree Lexing.Tokens; they can be created by calling the LNode.Trivia function. Since an LNode is not allowed to have both a Name and a Value (as there is no syntax in LES or EC# for such a node), a trivia node pretends that there is an argument list with one item, and that one item is always a literal whose Value is the value stored in the trivia node. Thus, a token node is printed out as TokenType(Value) where Value is some literal.

If you suspect you're dealing with a trivia node, it is wasteful to actually call node.Args[0].Value since this causes a temporary token list to be allocated. Instead you should use this property, which returns the token value without allocating memory. Of course, if this property is called on a non-trivia node, it simply returns Args[0].Value.

abstract object Loyc.Syntax.LNode.Value

get

Returns the value of a literal node, or NoValue.Value if this node is not a literal (IsLiteral is false).

Referenced by Loyc.LLParserGenerator.IntStreamCodeGenHelper.CodeToTerminalPred(), and Loyc.LLPG.Macros.LLLPG_parser().

Documentation moved to ecsharp.net

Remarks

Background information

The reimplementation

Important properties

Note

Nested classes

Public static fields

Properties

Public Member Functions

Static Public Member Functions

Protected Member Functions

Static Protected Member Functions

Protected fields

Member Function Documentation

Property Documentation