blitz-research
Missbehaviour with EachIn on arrays
Hello!
I noticed a weird behaviour when using a simple array (array of basic variable type, or array of simple struct).
When using: For Local i := 0 to Array.Length - 1 .. Next it acts as intended... But when using: For Local t := EachIn Array ... Next
it doesn't affect the array contents... So it seems that it affects the array's item CONTENT to t instead of it's pointer, which seems odd to me, since when we use EachIn, it sounds obvious we want the pointer to be affected, so we can both read and write the array content.
Here is a little simple "labtest" to demonstrate it:
Namespace test
#Import "<std>"
#Import "<mojo>"
Using std..
Using mojo..
Struct Test
Field X:Int = 0
Field Y:Int = 0
End Struct
Global instance:AppInstance
Global test:Test
Global X:Int = 0
Global Y:Int = 0
Global structarray:Test[] = New Test[1]
Global nonstructarray:Int[] = New Int[1]
Class MyWindow Extends Window
Method New()
Super.New("Test", 320, 200)
End Method
Method Update()
If Keyboard.KeyReleased(Key.Escape) Then instance.Terminate()
structtest(test)
structtest(structarray[0])
nonstructtest(X)
Y += 1
test.Y += 1
structarray[0].Y += 1
For Local t := Eachin structarray
t.X += 1
Next
For Local t := Eachin nonstructarray
t += 1
Next
End Method
Method structtest(t:Test)
t.X += 1
End Method
Method nonstructtest(t:Int)
t += 1
End Method
Method OnRender( canvas:Canvas ) Override
App.RequestRender()
Update()
canvas.DrawText("Struct.X: " + test.X, 10, 10)
canvas.DrawText("Struct.Y: " + test.Y, 10, 22)
canvas.DrawText("Non Struct X: " + X, 10, 34)
canvas.DrawText("Non Struct Y: " + Y, 10, 46)
canvas.DrawText("Array of Struct X (EachIn): " + structarray[0].X, 10, 58)
canvas.DrawText("Array of non-Struct (EachIn): " + nonstructarray[0], 10, 70)
End Method
End Class
Function Main()
instance = New AppInstance
New MyWindow
App.Run()
End Function
End Namespace
So, is this an issue ? Or is a such behaviour intended for some reasons ?
Eachin with arrays returns a copy of each array element, not a 'reference' or 'pointer' of any kind. So this code:
For Local t := Eachin nonstructarray t += 1 Next
Is really just incrementing a tempory copy of each array element and then throwing it away!
On Mon, Aug 20, 2018 at 11:23 PM madgician-vd [email protected] wrote:
Hello!
I noticed a weird behaviour when using a simple array (array of basic variable type, or array of simple struct).
When using: For Local i := 0 to Array.Length .. Next it acts as intended... But when using: For Local t := EachIn Array ... Next
it doesn't affect the array contents... So it seems that it affects the array's item CONTENT to t instead of it's pointer, which seems odd to me, since when we use EachIn, it sounds obvious we want the pointer to be affected, so we can both read and write the array content.
Here is a little simple "labtest" to demonstrate it:
`Namespace test #Import "" #Import ""
Using std.. Using mojo..
Struct Test Field X:Int = 0 Field Y:Int = 0 End Struct
Global instance:AppInstance Global test:Test Global X:Int = 0 Global Y:Int = 0
Global structarray:Test[] = New Test[1] Global nonstructarray:Int[] = New Int[1]
Class MyWindow Extends Window
Method New() Super.New("Test", 320, 200) End Method
Method Update() If Keyboard.KeyReleased(Key.Escape) Then instance.Terminate() structtest(test) structtest(structarray[0]) nonstructtest(X) Y += 1 test.Y += 1 structarray[0].Y += 1 For Local t := Eachin structarray t.X += 1 Next For Local t := Eachin nonstructarray t += 1 Next End Method
Method structtest(t:Test) t.X += 1 End Method
Method nonstructtest(t:Int) t += 1 End Method
Method OnRender( canvas:Canvas ) Override App.RequestRender() Update() canvas.DrawText("Struct.X: " + test.X, 10, 10) canvas.DrawText("Struct.Y: " + test.Y, 10, 22) canvas.DrawText("Non Struct X: " + X, 10, 34) canvas.DrawText("Non Struct Y: " + Y, 10, 46) canvas.DrawText("Array of Struct X (EachIn): " + structarray[0].X, 10, 58) canvas.DrawText("Array of non-Struct (EachIn): " + nonstructarray[0], 10, 70)
End Method
End Class
Function Main() instance = New AppInstance New MyWindow App.Run() End Function
End Namespace `
So, is this an issue ? Or is a such behaviour intended for some reasons ?
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