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3016 :: Some proc var return value confusion

• Stefan_Salewski (orginal) [2017-06-22T12:19:40+02:00] view original

  I just compared proc names and signature of my local robin hood hash table with Nim's table implementation.

  In the later we have

  proc `[]`*[A, B](t: var Table[A, B], key: A): var B {.deprecatedGet.} =
    ## retrieves the value at ``t[key]``. The value can be modified.
    ## If `key` is not in `t`, the ``KeyError`` exception is raised.
    get(t, key)
  
  proc `[]=`*[A, B](t: var Table[A, B], key: A, val: B) =
    ## puts a (key, value)-pair into `t`.
    putImpl(enlarge)
  Run

  For me it is not really obvious which of both is called when I would write something like

  myTable["myExistingString"] = myIntValue
  
  Run

  Both procs seems to allow assignment, if key already exists in table. Is the undocumented {.deprecatedGet.} pragma important for behaviour?

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• Parashurama (orginal) [2017-06-22T13:00:40+02:00] view original

  As far as I know, proc [] returning var can only be used in this kind of expression

  list[index].this_proc_require_var_arg()
  Run

  deprecatedGet looks like a custom pragma to change behaviour depending on compile time flags

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