Zeke Medley a3001f1b2b Add lambda expressions with closures to Zeek. ... This allows anonymous functions in Zeek to capture their closures. they do so by creating a copy of their enclosing frame and joining that with their own frame. There is no way to specify what specific items to capture from the closure like C++, nor is there a nonlocal keyword like Python. Attemptying to declare a local variable that has already been caught by the closure will error nicely. At the worst this is an inconvenience for people who are using lambdas which use the same variable names as their closures. As a result of functions copying their enclosing frames there is no way for a function with a closure to reach back up and modify the state of the frame that it was created in. This lets functions that generate functions work as expected. The function can reach back and modify its copy of the frame that it is captured in though. Implementation wise this is done by creating two new subclasses in Zeek. The first is a LambdaExpression which can be thought of as a function generator. It gathers all of the ingredients for a function at parse time, and then when evaluated creats a new version of that function with the frame it is being evaluated in as a closure. The second subclass is a ClosureFrame. This acts for most intents and purposes like a regular Frame, but it routes lookups of values to its closure as needed.		2019-06-20 18:43:56 -07:00
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out	Add lambda expressions with closures to Zeek.	2019-06-20 18:43:56 -07:00