c# - 如何定义 "else" block ？

Question

这是我正在尝试的:

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，它不应该贪婪地捕获“其他”吗？不太确定如何定义 else block ，使其只能后跟一个“if” block 。

我认为带有 if 节点和 else 节点的 if_else block 节点是最佳的，因为那样我就不必去当我尝试遍历 AST 时返回并检查前一个兄弟节点。

如果您需要查看更多语法...请告诉我。 “ block ”基本上定义为 { blah }({} 之间的一堆语句)。

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尝试将其作为可选 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;

也不喜欢。仍然抛出警告。

Answer 1

没关系...Irony 有这个神奇的 PreferShiftHere() 函数可以解决这个问题。

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;
if_else.Rule = if_condition + PreferShiftHere() + "else" + block;
preset_directive.Rule = foreach_in | foreach_as | for_loop | if_else | if_condition;
directive_blk.Rule = preset_directive | custom_directive;