CONST in a CLASS?

Monkey Forums/Monkey Programming/CONST in a CLASS?

ENAY	(Posted 2011) [#1]

Is it possible to have a const array inside a class? It doesn't seem to be working for me.

The following code works fine:-

Const MOO  :Float[3]
Const PARP :Int = 0

so does:-

Const MOO  :Float[3]

Class WHOOP
   Const PARP :Int = 0
End

however this doesn't work:-

Class WHOOP
   Const PARP :Int = 0
   Const MOO  :Float[3]
End

I get the error:-

"Compile Error

<Expr> cannot be statically evaluated"

I am guessing then for whatever reason it isn't possible to have an array of CONST variables inside a class?

wiebow

(Posted 2011) [#2]

The problem is the array. You're declaring an empty array. Comment it out, or try adding values to it like:

Const MOO:Float[3]=[1.0,2.0,3.0]

ENAY	(Posted 2011) [#3]

Hi Wiebo, thanks for the post.

I tried that first too before I posted here.

If I copy that into a class I get:-

"Compile Error

Syntax error - expecting class member declaration."

wiebow

(Posted 2011) [#4]

This works over here: Const a:Int[] = [1,2,3]

ENAY	(Posted 2011) [#5]

Hi Weibo, after much hunting and testing I finally figured it out. I think it might be a Monkey bug. Declaring it works (anywhere) but it fails to declare when you try to use it anywhere in the code.

Try this:-

Import mojo

Const temp_float1:Float[] = [1.0,2.0,3.0]

Class Moo
	Const temp_float2:Float[] = [1.0,2.0,3.0]
	Field temp_x:Float[3]
End

Class TestGame Extends App
	Field TheMoo:Moo
		
	Method OnCreate ()
	  	TheMoo = New Moo
	End
	
	Method OnUpdate ()
		For Local i:Int = 0 To 2
			'TheMoo.temp_x[i] += TheMoo.temp_float2[i]
			'TheMoo.temp_x[i] += temp_float1[i]
		Next
	End
	
	Method OnRender ()
		
	End
End

Function Main ()
	New TestGame
End

It will compile unless you comment out either of the lines inside the OnUpate loop. So clearly they aren't being created properly (or at all)

Trivial of course but not using a const array works fine

Import mojo

Class Moo
	Const temp_float1:Float = 1.0
	Const temp_float2:Float = 2.0
	Const temp_float3:Float = 3.0
	
	Field temp_x:Float[3]
End

Class TestGame Extends App
	Field TheMoo:Moo
		
	Method OnCreate ()
	  	TheMoo = New Moo
	End
	
	Method OnUpdate ()
		TheMoo.temp_x[0] += TheMoo.temp_float1
		TheMoo.temp_x[1] += TheMoo.temp_float2
		TheMoo.temp_x[2] += TheMoo.temp_float3
	End
	
	Method OnRender ()
		
	End
End

Function Main ()
	New TestGame
End

Foppy

(Posted 2011) [#6]

It looks like it is impossible to create a constant array of floats.

Const UNIT_SPEED:Float[] = [0.1,0.2,0.3]

This results in "Expression cannot be statically evaluated", outside of a class as well.

Foppy

(Posted 2011) [#7]

In which case I guess something like this would be a practical alternative:

Const UNIT_BASE_SPEED:Float = 0.1

Const UNIT_SPEED:Int[] = [1,2,3]

Local mySpeed:Float = UNIT_BASE_SPEED*UNIT_SPEED[2]

Computing the float from a base number and an int multiplier...

Edit: Whoops, that gives the same error message. So a constant array of ints also isn't allowed. I am using MonkeyPro 38.

skid	(Posted 2011) [#8]

This has never worked for me, just use Global instead.