array in struct bug?

[abakoboParticipant]

this code shows an array modified in the orriginal struct though the struct was/should_be passed by value to the function..

Monkey

[crayon-5cba8d8796cb8328299188 inline="true" ] #Import "<std>" Using std.. Struct structor Field x:Int Field y:Int Field arr:=New Int[20] Method New(a:Int,b:Int) x=a y=b End End Function modarr(s:structor) s.arr[5]=77 s.x=77 End Function Main() Local s:=New structor(0,0) Print "the array contained in the struct is modified by a function that received the struct by value" Print "is it normal ?" s.arr[5]=5 s.x=5 Print s.arr[5] Print s.x modarr(s) Print s.arr[5] 'modified Print s.x'not modified End

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[crayon-5cba8d8796cb8328299188 inline="true" ] #Import "<std>"   Using std..   Struct structor Field x:Int Field y:Int Field arr:=New Int[20] Method New(a:Int,b:Int) x=a y=b End End   Function modarr(s:structor) s.arr[5]=77 s.x=77 End   Function Main() Local s:=New structor(0,0)   Print "the array contained in the struct is modified by a function that received the struct by value" Print "is it normal ?"   s.arr[5]=5 s.x=5 Print s.arr[5] Print s.x modarr(s) Print s.arr[5] 'modified Print s.x'not modified End

[/crayon]

[codifiesParticipant]

Field arr:=New Int[20]

isn’t that in effect a pointer, so the pointer isn’t modified but rather what it points to (which isn’t actually in the struct) ie **New** Int[]

[abakoboParticipant]

Yes and no ;P, but i thought that it would create a full copy so the pass by value would be consistent..

[codifiesParticipant]

The problem is that the array isn’t actually physically in the struct and good job because it would be copying the whole array each time you passed it anywhere…

I definitely think structs are useful for just small collections primitives for example four values defining a rectangle, trying to use it as light weight class is going to be more trouble than its worth…

[abakoboParticipant]

Indeed

[Mark SiblyKeymaster]

Arrays types are, like objects, reference types so are never ‘value copied’.

[Author]

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