restricting floating point range

[Dave Novo 48]

Hello,

I know I can do the following to restrict the valid range of integer variables.

 

TNBType= 1..2;

Can I do something similar with floating point. For example, I want to restrict the values of a double precision variable to be between 0.0 to 1.0. I have tried the following

TProbabilityValue=0.0..1.0;
TProbabilityValue:double=0.0..1.0;
TProbabilityValue:double=0..1;

none of the above seem to work. I guess this is not possible, but I figured I would ask.

[David Heffernan 2300]

3 minutes ago, Dave Novo said:

Can I do something similar with floating point.

No. No language or library support for anything like this. 

[David Schwartz 415]

There's always the InRange function

 

https://docwiki.embarcadero.com/Libraries/Alexandria/en/System.Math.InRange

 

function InRange(const AValue, AMin, AMax: Integer): Boolean;
function InRange(const AValue, AMin, AMax: Int64): Boolean;
function InRange(const AValue, AMin, AMax: UInt64): Boolean;
function InRange(const AValue, AMin, AMax: Single): Boolean;
function InRange(const AValue, AMin, AMax: Double): Boolean;
function InRange(const AValue, AMin, AMax: Extended): Boolean;

[Rollo62 502]

Probably you could use a class helper with specific access methods to mimick that behavior. 

[Der schöne Günther 306]

It's pretty verbose, but you can add your own struct with operator overloading (implicit assignment) that can throw an EArgumentOutOfRangeException when you try to stuff values outside of [0.0, 1.0] into it.

 

While you're at it, you can overload the equality operator as well for just the precision

you need.

 

Or perhaps the add operator as well. So that adding 0.75 with 0.40 will result in 1.0. It depends on how you use these values.

 

I'm sure the compiler is clever and won't even allocate more than the needed 4 bytes for the float.

Edited February 18, 2023 by Der schöne Günther

[Dave Novo 48]

Thanks for the suggestions. I was looking for compiler support instead of rolling my own, but all the suggestions above are great.