CODEWITHSUNDEEP
delphi
Guy Gordon
Guy Gordon

Reputation: 740

How to eliminate duplicate constants in Delphi?

I have code using two constants, each describing the size of an array in different ways:

const  ArraySize = 1024;
       ArrayBits = 10;    //2^10 = 1024 bits

How do I express one of these in terms of the other? The compiler will not allow use of Log2 or LdExp in constants.

Answers for any version of Delphi are OK.

Upvotes: 1

Views: 215

Answers (2)

user743382
user743382

Reputation: 

const
  ArrayBits = 10;
  ArraySize = 1 shl ArrayBits;

The value of a shl b is equal to a * 2^b, so 1 shl ArrayBits is equal to 2^ArrayBits.

Upvotes: 8

David Heffernan
David Heffernan

Reputation: 612894

Well, you could do this:

const  
  ArrayBits = 10;
  ArraySize = 1 shl ArrayBits;

But I probably would shy away from that. It feels a little too obscure for me. In my opinion you should use arithmetic operators when you are performing arithmetic.

I'd probably leave your code as it is and add an assertion in the runtime code that the two constants were appropriately related. Document it with a comment as well.

Upvotes: 9

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