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17 lines
1.2 KiB
17 lines
1.2 KiB
/* Takes an AST and converts all of the functions into closures.
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* A closure is a pair of two things: an environment and a function
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* The closure has the property that all of the free variables of the function
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* are in the environment, or an exception is raised because the variable is not bound
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* in the current environment.
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* A free variable is simply those that are not in the list of formal parameters.
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* We start with the global environment and traverse the AST. Every time a new function is entered
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* the current environment gets extended with the formal parameters of the function.
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* When a let is encountered the current environment also gets extended.
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* The algorithm continues for any further function definitions in that branch
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* otherwise it just stops for that particular branch and continues with the rest of the AST
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*
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* Therefore in order to call a closure one must first extract the actual function and then
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* call the function with the environment associated with it.
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* For the purposes of type checking it does not matter how the function gets called, the environment
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* is only used for looking up the types of names. Formal parameters are given type variables.
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*/
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