How do I assert a single ?

[dormky 4]

Consider :

 

procedure Test();
var
  number: single;
begin
  number := 0.96493138416; // Too long for a single precision
  // Assert(number = 0.96493138416); // Will fail, normal
  number := RoundTo(number, -3);
  Assert(number = 0.965); Fails
end;

Here number is supposed to be a value I'm getting from the data I'm running the test on. Due to binary representation the number will never be exactly correct, however trying to Assert with the value given by the debugger doesn't work either. So how am i meant to assert on floats ?

 

Thanks.

[Cristian Peța 117]

Maybe using SameValue(number, 0.965, 0.001)?

Or if you need all the precision the test binary.

[Anders Melander 2007]

Multiply by a 10^"number of decimals", Trunc to convert to integer, Assert on the integer value

[David Heffernan 2441]

It depends a bit on what your goals are. But if you want to test equality then you need to put the expected value into a single. That's hard to do in a compiler because delphi literal syntax doesn't allow to specify the type of a floating point literal. You could declare a typed constant of single type and compare against that. 

[dormky 4]

Ended up landing on this, works fine for my purpose :

procedure AssertFloat(const value, should: Extended);
begin
  Assert(Abs(value - should) < 0.00001);
end;

 

[dummzeuch 1644]

What's wrong with

Assert(SameValue(Value, Should))

Or, if you want to set the maximum allowed difference yourself

Assert(SameValue(Value, Should, MaxDelta))

Edit: @Cristian Peța already suggested that.

Edited 23 hours ago by dummzeuch

[David Heffernan 2441]

Every time someone calls SameValue a puppy dies

[dummzeuch 1644]

15 hours ago, David Heffernan said:

Every time someone calls SameValue a puppy dies

OK, I bite: What's the problem with SameValue?

[Rollo62 581]

21 hours ago, Anders Melander said:

Multiply by a 10^"number of decimals", Trunc to convert to integer, Assert on the integer value

I do the same in many places, even keeping Integers for example by the Factor 10000 stored somewhere in the first place,
but then you must ensure that it never happens that there is an unexpected overflow of the Integer.
Thats why this solution always leaves me with a bad feeling, when I used it, ... but there's no such thing as a free lunch