Thanks David, please see inline. On Wed, Dec 1, 2010 at 6:09 PM, David Van Horn <dvanh...@ccs.neu.edu> wrote:
> >> This is not entirely true, but substitution and effects are subtle. > I can see that it works if things are by-reference, but by-value will appear to be broken, no? > * it does not address closure >> > > You don't need closures in a substitution model. Not sure if I understand what you mean, but I mean I need to implement closure, and substitution does not appear to have advantage over simply stuffing the values into the environment for a delayed evaluation in an interpreter. Perhaps a better rephrase for the whole question is: what's a good place to hold the values needed for the interpreter to perform substitution/evaluation? In the environment? In the call frame? I am getting the feeling that I need my own call frame and stack even in an minimal interpreter. Maybe I am looking too far ahead, but it seems like I cannot get away >> from needing my own call stack? Or am I missing something? >> > > I'm not exactly sure what you mean about your own call stack. The > environment and the control stack are separate issues. I agree that they are separate issues, but as the implementer I need to consider them together to have a full solution. I.e. what are all of the components I need to implement in order to have a minimal interpreter (primitive types, lambda, define, set, quote, if) without using Racket's built-in eval. Thanks, yc
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