Modular•7mo ago

Best way to make a struct of CollectionElements to conform to CollectionElement.

I am still confused about best practices for __moveinit__ and __copyinit__. Let's say i have a struct with two variables, which are both structs which conform to the CollectionElement trait, how to define __moveinit__ and __copyinit__ for this struct. Will this do?

struct A:
  var b:B    # B conforms to CollectionElement
  var c:C    # C conforms to CollectionElement
  fn __init__(...

  fn __copyinit__(inout self, existing: Self):
      # ????
      self.b = existing.b
      self.c = existing.c
    
  fn __moveinit__(inout self, owned existing: Self):
      # ???
      self.b = existing.b
      self.c = existing.c

struct A:
  var b:B    # B conforms to CollectionElement
  var c:C    # C conforms to CollectionElement
  fn __init__(...

  fn __copyinit__(inout self, existing: Self):
      # ????
      self.b = existing.b
      self.c = existing.c
    
  fn __moveinit__(inout self, owned existing: Self):
      # ???
      self.b = existing.b
      self.c = existing.c

Any advice highly appreciated

2 Replies

Ryulord•7mo ago

Unless you're doing anything special this should work just fine. moveinit and copyinits like this are so common that it's why we have @value. Almost every struct I write uses the value decorator.

drujensen•7mo ago

sometimes I see in the moveinit a caret ^ symbol at the end of the assignment.

    fn __moveinit__(inout self, owned other: Graph):
        self.inputs = other.inputs^
        self.params = other.params^
        self.nodes = other.nodes^
        self.outputs = other.outputs^
        self.loss_out = other.loss_out
        self.symbol_count = other.symbol_count

    fn __moveinit__(inout self, owned other: Graph):
        self.inputs = other.inputs^
        self.params = other.params^
        self.nodes = other.nodes^
        self.outputs = other.outputs^
        self.loss_out = other.loss_out
        self.symbol_count = other.symbol_count

Does that mean copy the address instead of the value? If so, why not do this for all the fields? Is it something to do with primitive types? nm, found the answer about ^ here: https://discord.com/channels/1087530497313357884/1247713442190721114/1247715698092802119

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Best way to make a struct of CollectionElements to conform to CollectionElement.