> If the language has closures as first-class objects that can be passed as arguments or returned from other functions, the closure will need to be represented by a data structure that captures the bindings of the free variables.
You might get the idea that the article is talking about getting rid of closures, i.e. an implicit data structure containing the closed over environment that lambdas have access to when called, and turning the captured variables into explicit arguments. But most interesting languages that have lambdas support closures as first class values, so you end up with explicit data carriers throughout even with lambda lifting. You just switch from whatever your existing closure representation was, to data structures containing a function pointer and a closure structure - which is often your existing closure representation already.
> If the language has closures as first-class objects that can be passed as arguments or returned from other functions, the closure will need to be represented by a data structure that captures the bindings of the free variables.
You might get the idea that the article is talking about getting rid of closures, i.e. an implicit data structure containing the closed over environment that lambdas have access to when called, and turning the captured variables into explicit arguments. But most interesting languages that have lambdas support closures as first class values, so you end up with explicit data carriers throughout even with lambda lifting. You just switch from whatever your existing closure representation was, to data structures containing a function pointer and a closure structure - which is often your existing closure representation already.