Mirror of forum.nim-lang.org

7699 :: using expressions in default values for procedure's parameters

• pietroppeter (orginal) [2021-03-25T10:10:34+01:00] view original

  I know that nim can use expressions for default values in procedures (saw it somewhere in stdlib), but until today I never realized that I could also make use of other parameters in the expression.

  Example:

  proc ape(a: string, b: string = ("no" & a)): string = "🐒 " & a & b
  echo ape("bo")
  Run

  output:

  
  🐒 bonobo
  Run

  I find it an extremely cool feature, but I was not able to find a reference in the documentation of this (well, I checked Manual and Tutorial), not even for the fact that you can use expression in parameters. Anyone knows a documentation source for this? Are there any gotchas about it? Happy to make a doc PR somewhere if it can improve visibility of this feature.

---

• DeletedUser (orginal) [2021-03-25T10:48:26+01:00] view original

  It was probably not documented because there was no guarantee of this being a stable feature. If it's considered to be a reliable and working feature, then it could be added to the manual, otherwise I believe the experimental manual would be where it goes.

---

• Yardanico (orginal) [2021-03-25T10:50:21+01:00] view original

  It's mentioned in https://github.com/nim-lang/Nim/wiki/Lesser-known-Nim-features#using-complex-expressions-based-on-other-arguments-as-default-arguments-in-procedures :)

---

• halloleo (orginal) [2021-03-26T01:00:44+01:00] view original

  Cool feature indeed. - Not sure how often I will have a use for it though....

---