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3311 :: compile time 'asserts'

• jackmott (orginal) [2017-11-05T19:29:16+01:00] view original

  What would be the idiomatic way to do something like a compile time assert.

  Say that you had proc foo(bar:int) where you want to restrict bar to values 1,3,5 and 8. I don't think you can use a range here because they are not contiguous. But you could use a when to check at compile time, but what is the best way to cause a compile error when it doesn't match?

  Also is there a nice way you could also cause an error at runtime with debug builds?

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• Varriount (orginal) [2017-11-05T19:37:10+01:00] view original

  Well, the only way to do type checking like this is through static analysis, which is typically performed by the compiler. The other way to do this is to make a variant of a procedure that accepts static parameters, and then use when to test their value.

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• mratsim (orginal) [2017-11-05T20:59:08+01:00] view original

  Here you go

  const allowedInts = {1, 3, 5, 8}
  
  proc foo(bar:static[int]) =
    static: assert bar in allowedInts, "Value " & $bar & " not allowed"
    echo "Success"
  
  foo(6)
  Run

  const allowedInts = {1, 3, 5, 8}
  
  proc foo(bar:static[int]) =
    static: assert bar in allowedInts, "Value " & $bar & " not allowed"
    echo "Success"
  
  foo(5)
  Run

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