我如何定义“其他”？堵塞？
这就是我正在尝试的：
foreach_in.Rule = ToTerm("foreach") + "(" + VARIABLE + "in" + list_obj + ")";
foreach_as.Rule = ToTerm("foreach") + "(" + list_obj + "as" + VARIABLE + ")";
for_loop.Rule = ToTerm("for") + "(" + simple_assignment + ";" + comparison + ";" + assignment + ")";
if_condition.Rule = ToTerm("if") + "(" + comparison + ")";
if_else.Rule = if_condition + block + "else"; // <-- PROBLEM
preset_directive.Rule = foreach_in | foreach_as | for_loop | if_else | if_condition;
directive.Rule = preset_directive | custom_directive;
directive_blk.Rule = directive + block;
但是我遇到了 shift-reduce 冲突。我不太清楚为什么......如果可以的话，它不应该贪婪地抓住“其他”吗？不太确定如何定义 else 块，使其后面只能跟一个“if”块。
我认为带有 if 节点和 else 节点的 if_else 块节点将是最佳选择，因为这样我就不必返回并检查当我尝试遍历 AST 时，它是前一个兄弟。
如果您需要查看更多语法...请告诉我。 “块”基本上定义为 { blah } （{} 之间的一堆语句）。
尝试将其作为可选块：
custom_directive_kw.Rule = ToTerm("custom_directive1") | "custom_directive2";
custom_directive.Rule = custom_directive_kw + free_args_opt;
foreach_in.Rule = ToTerm("foreach") + "(" + variable + "in" + list_obj + ")" + block;
foreach_as.Rule = ToTerm("foreach") + "(" + list_obj + "as" + variable + ")" + block;
for_loop.Rule = ToTerm("for") + "(" + simple_assignment + ";" + comparison + ";" + assignment + ")" + block;
if_condition.Rule = ToTerm("if") + "(" + comparison + ")" + block + else_blk_opt;
else_blk.Rule = "else" + block;
else_blk_opt.Rule = else_blk | Empty;
preset_directive.Rule = foreach_in | foreach_as | for_loop | if_condition;
directive.Rule = preset_directive | custom_directive;
directive_blk.Rule = directive;
也不喜欢那样。仍然发出警告。
Here's what I'm trying:
foreach_in.Rule = ToTerm("foreach") + "(" + VARIABLE + "in" + list_obj + ")";
foreach_as.Rule = ToTerm("foreach") + "(" + list_obj + "as" + VARIABLE + ")";
for_loop.Rule = ToTerm("for") + "(" + simple_assignment + ";" + comparison + ";" + assignment + ")";
if_condition.Rule = ToTerm("if") + "(" + comparison + ")";
if_else.Rule = if_condition + block + "else"; // <-- PROBLEM
preset_directive.Rule = foreach_in | foreach_as | for_loop | if_else | if_condition;
directive.Rule = preset_directive | custom_directive;
directive_blk.Rule = directive + block;
But I get a shift-reduce conflict. I'm not quite sure why... shouldn't it greedily grab the "else" if it can? Not quite sure how else to define an else block such that it can only be followed by an "if" block.
I think an if_else block node with an if node and an else node would be optimal because then I don't have to go back and check the previous sibling when I try traverse the AST.
If you need to see more of the grammar...just let me know. A "block" is basically defined as { blah } (a bunch of statements between {}).
Trying it as an optional block:
custom_directive_kw.Rule = ToTerm("custom_directive1") | "custom_directive2";
custom_directive.Rule = custom_directive_kw + free_args_opt;
foreach_in.Rule = ToTerm("foreach") + "(" + variable + "in" + list_obj + ")" + block;
foreach_as.Rule = ToTerm("foreach") + "(" + list_obj + "as" + variable + ")" + block;
for_loop.Rule = ToTerm("for") + "(" + simple_assignment + ";" + comparison + ";" + assignment + ")" + block;
if_condition.Rule = ToTerm("if") + "(" + comparison + ")" + block + else_blk_opt;
else_blk.Rule = "else" + block;
else_blk_opt.Rule = else_blk | Empty;
preset_directive.Rule = foreach_in | foreach_as | for_loop | if_condition;
directive.Rule = preset_directive | custom_directive;
directive_blk.Rule = directive;
Doesn't like that either. Still throws the warning.
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没关系... Irony 有这个神奇的
PreferShiftHere()函数可以做到这一点。Nevermind... Irony has this magical
PreferShiftHere()function that does the trick.我在这里猜测，但你不应该将 IF 定义为：
然后继续将 else 部分定义为：
最后把它们放在一起：
再一次，我在这里猜测，因为我还没有工作还没有使用 EBNF。
I'm guessing here, but shouldn't you define the IF as:
And then go on to define the else part as:
And Finally put it all together:
Once more, I'm guessing here, 'cause I haven't worked with EBNF yet.