Arbitrary CONST values

[ahenry3068]

@ahenry3068

I think Charlie is saying 
Const MyDate$ = Date$, MyTime$ = Time$

These will remain constant through Run of the program, even though every time you start a new run they will be different. So there is that too!

     Yes.   I get what he said.   That is exactly as I understood it.    Those things are still not known at compile time though.  
Being known at compile time and NOT CHANGING ever is the whole point of a CONSTANT in any programming language.

  Allowing the code you put above would be contrary to the whole purpose of having a CONSTANT directive.      

I've been doing a whole lot of assembly code lately, maybe that's why I feel so strongly about this.   

We are talking about what machine code is generated.   


When you use a CONSTANT value the code generated is like this

CONST FOUR=4
X = FOUR       
D = FOUR

Would generate the EXACT same code as

X = 4
D = 4

ML CODE WOULD BE LIKE

LOAD REGISTER IMMEDIATE VALUE 4
STORE REGISTER AT ADDRESS X

LOAD REGISTER IMMEDIATE VALUE 4 ; this could possibly even be eliminated with a good code optimizer, but would probably be there without
optimization. Immediate register loads are usually much faster than Memory loads too.
STORE REGISTER AT ADDRESS D




THIS: 

DIM X AS INTEGER
X = 4
D = X 

Would generate quite different and more complex code at the machine level. 

LD REGISTER WITH IMMEDIATE VALUE 4
STORE REGISTER AT ADDRESS X

LD SRC POINTER REGISTER WITH ADDRESS OF X
LD DEST POINTER REGISTER WITH ADDRESS OF D

MOV VALUE AT SRC POINTER TO DEST POINTER LOCATION


This is a pretty simple example. But the whole point of CONSTANT declarations is to speed up and simplify the generated code !



Charlie is missing the point of constants.
What he wants would make it NO LONGER A CONSTANT !