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1 point by bramsundar 6102 days ago | link | parent

I'm still a noob, and my idea could be completely off base, but I think that it could be possible to devise a system that allows something like optional namespaces. The idea would be to have each symbol in the environment map to a table rather than directly to a function or variable. The table could have one entry per type (for example, pat's table could have one entry that's a macro, one that's a function, and one that's a variable). In standard cases, the value lookup function could return the entry that was last added to the hash table and thus mimic a Lisp-1 for all purposes. However, if the programmer specifies the type of a symbol, then the table would return the corresponding entry. There could be an fairly unobtrusive syntax for this. In one such syntax, the symbol pat would be:

pat (standard usage) #pat (function pat) `pat (macro pat) @pat (variable pat)

Then, pat-match:def would become `pm:def.



1 point by almkglor 6102 days ago | link

No, my friend, the problem is the order of evaluation.

  (let pm (table)
      (pm 1))
  (mac pm ...)
versus:

  (mac pm ...)
  (let pm (table)
     (pm 1))
Unless you qualifiy everything with syntactic modifiers, order of evaluation will matter, and matter horribly.

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1 point by bramsundar 6102 days ago | link

I'm sorry, but could you explain your example a bit more? I don't think that I understand the issue here. If pm is redefined as a table through the let, why wouldn't we be able to access the macro version through the modifier? the table would clobber the variable version (@pm), but not the macro version right?

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2 points by almkglor 6102 days ago | link

Local variables never override macros. In the first case above, the let will return the expected value correctly, because pm at that time hasn't been defined yet. In the second case, it will not return the expected value, because pm is defined as a macro, and (pm 1) gets replaced with whatever (pm 1) expands to, let notwithstanding.

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