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5952 :: reader macro

• jdn (orginal) [2020-02-19T23:35:20+01:00] view original

  Is there any equivalent to a reader macro in nim? I wrote an expression parser and evaluator in nim which was very easy to do. To get better performance I thought that since nim has macro's I can leverage that without too much trouble. However, walking the AST of my expression parser to create nim AST (in macros) requires compile time proc's for recursion and so I have a chicken and egg problem that I can't seem to resolve.

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• Varriount (orginal) [2020-02-20T03:17:10+01:00] view original

  Do you mean something like NPeg?

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• mratsim (orginal) [2020-02-20T10:33:12+01:00] view original

  Proc with a "NimNode" input are automatically compile-time, otherwise you can tag them with {.compiletime.} pragma.

  Regarding implementing your own AST with an Expr AST -> Nim AST, you might also be interested into my step-by-step experiments into writing a compiler in Nim macros: https://github.com/mratsim/compute-graph-optim which now lives as a PoC tensor/matrix operation compiler: https://github.com/numforge/laser/tree/master/laser/lux_compiler.

  The AST implementation is described here: https://github.com/numforge/laser/blob/master/laser/lux_compiler/core/low_level_design_considerations.md

  It's still unfinished so there is only about 1000 lines so should be pretty easy to follow.

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• jdn (orginal) [2020-02-20T16:00:13+01:00] view original

  Awesome, thank you very much for the links. Converting my AST to Nim AST is not my issue. It is putting that Nim AST into a macro to get it to compile which I'm struggling. I think I follow the basic logic in your compile macro although I haven't tried to sort out with my code. I'll report back when I give it a shot. Thanks again for the links!

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• andrea (orginal) [2020-02-20T17:34:35+01:00] view original

  Do you produce your AST at runtime? Because macros are run at compile time, so that's too late. It sounds like you are trying to use Nim macros like a JIT, if I understand correctly

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