Why can I divide Single by Variant in Delphi, and what is it for?

Question

I was surprised to see, that floating-point values could be divided by a Variant in Delphi. A simple example of what can be done:

var
  v: Variant;
begin
  v := 2.3;
  Tag := 5.1 div v; // 2
  Tag := 5.1 mod v; // 1
  Tag := 5.1 div 2; // [dcc32 Error] E2015 Operator not applicable to this operand type
  Tag := 5.1 mod 2; // [dcc32 Error] E2015 Operator not applicable to this operand type
end;

It looks like Delphi rounds the left-part and right-part before doing the div/mod operation.

I would expect above code to produce errors at compile-time in all 4 lines, since my understanding is that div/mod are not applicable to floating-point values no matter what. Clearly this is not the case.

Why can I divide Single by Variant in Delphi, and what is it needed for?

Answer 1

From Variants in Expressions:

If an expression combines variants with statically-typed values, the statically-typed values are automatically converted to variants.

This means that the float typed literal is converted to a variant first.

Then both variants are implicitly converted to integer values to match the operator before doing the div/mod operation. Variant Type Conversions

..and what is it needed for?

Just to be as versatile as possible and fully support OLE.