antlr3删除带有子树的treenode [英] antlr3 remove treenode with subtree
问题描述
我尝试使用antlr3.4进行一些树到树的转换
i try to do some tree to tree transform with antlr3.4
(对于这个问题)关于布尔表达式的是"AND"和"OR"被允许绑定到n个表达式. 解析器阶段会创建类似这样的内容
It's (for this question) about boolean expressions were "AND" and "OR" are allowed to bind to n expressions. The parser stage creates something like this
(OR
(AND (expr1) (expr2) (expr3)
(OR (AND (expr4))
(AND (expr5))
(AND (expr6))
)
)
)
不幸的是,存在"AND"和"OR"的AST节点仅绑定到一个表达式. (这没用,但是-规则,expr和orexpr被调用)
Unfortunately there are AST nodes for "AND" and "OR" that bind just to one expression. (Which is useless, but hey - rules andExpr and orExpr are invoked)
我试图将它们踢出(意思是,用它们的子节点替换它们),但是在树语法中却没有这样做. (顺便说一句:在纯Java中使用深度优先树遍历/修改,但这不是我的意图)
I tried to kick them out (mean, replace them by their subnodes) but fail to do so in a tree grammar. (BTW: Using a depth first tree traversal/modification in pure java works, but that's not my intention)
我尝试使用谓词,但似乎无法正确理解.
I tried to use predicates but i can't seem to get it right.
这是解析未经修改的流的语法
This is the grammar to parse the stream unmodified
start :
orExpr^ EOF!
;
orExpr :
^(OR r+=andExpr+ ) -> ^(OR $r)
;
andExpr :
^(AND unaryExpr+ )
;
notExpr:
^( NOT unaryExpr)
;
unaryExpr :
.+ // it gets more complicated below this
;
我尝试了一个谓词来捕获一个子节点的情况,但是未能通过n> 1个未修改的情况
I tried a predicate to catch the one-subnode-case but fail to pass the n>1 case unmodified
orExpr @init { int N = 0; }
:
( ^(OR (r+=andExpr {N++;})+ ) {N==1}? -> $r)
;
任何想法如何正确执行?
Any Ideas how to do it right?
附带的是语法分析器语法,它几乎是相同的...
edit: Attached is the parser grammar which is pretty much the same...
start
: '('! orExpr^ ')'! EOF! ;
orExpr
: a+=andExpr ( OR_T a+=andExpr )* -> ^(OR $a+ ) // 'AND' and 'OR' are multivalent
;
andExpr
: u+=unaryExpr ( AND_T u+=unaryExpr )* -> ^(AND $u+ )
;
notExpr
: NOT_T unaryExpr -> ^( NOT unaryExpr)
;
unaryExpr
: '('! orExpr ')'! // -> ^( BRACE orExpr), brace not needed in the ast (but needed for propper parsing)
| notExpr
| internal^ // internal is very complex in itself
;
推荐答案
您可以直接在解析器中执行此操作.您确实需要创建更多解析器规则,以免在重写规则中混淆ANTLR(请参见内联注释):
You can do this directly in the parser. You do need to create some more parser rules as to not confuse ANTLR in the rewrite rules (see the inline comments):
grammar T;
options {
output=AST;
ASTLabelType=CommonTree;
}
start
: orExpr EOF! {System.out.println($orExpr.tree.toStringTree());}
;
orExpr
: (andExpr2 -> andExpr2) ((OR andExpr)+ -> ^(OR andExpr2 andExpr+))?
;
// You can't use `andExpr` directly in the `orExpr` rule otherwise the rewrite
// rule `-> ^(OR ... )` gets confused.
andExpr2 : andExpr;
andExpr
: (notExpr2 -> notExpr2) ((AND notExpr)+ -> ^(AND notExpr2 notExpr+))?
;
notExpr2 : notExpr;
notExpr
: NOT^ notExpr
| atom
;
atom
: '(' orExpr ')' -> orExpr
| ID
;
OR : '||';
AND : '&&';
NOT : '!';
ID : 'a'..'z'+;
SPACE : ' ' {skip();};
解析类似"a && b && c || d || f || g"
的输入将产生以下AST:
Parsing input like "a && b && c || d || f || g"
will produce the following AST:
树语法如下:
tree grammar TWalker;
options {
tokenVocab=T;
ASTLabelType=CommonTree;
}
start
: expr
;
expr
: ^(OR expr+)
| ^(AND expr+)
| ^(NOT expr)
| ID
;
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