Andrea Mauri wrote on Wed, 30 Sep 2015:
var
a, b: Double;
begin
a:= 5.1000000000000005;
b:= 5.1;
if samevalue(a, b) then // I get TRUE - right!
label1.Caption:= 'same value (variable): True'
else
label1.Caption:= 'same value (variable): False';
if samevalue(a, 5.1) then // I get FALSE -- I supposed
to get TRUE- bad!
That is because 5.1 cannot be represented exactly using floating
point. As a result, the compiler will parse it using the highest
precision available, which is probably the 80 bit extended type on
your target platform. Therefore, the second samevalue calls the
extended precision version of that routine, while the first one calls
the double precision version (since both arguments are double).
Depending on the value, the extended and double precision versions of
samevalue can indeed have different results. That's also the reason
for the outcome of your second test.
Jonas
PS: please don't cross-post to multiple lists.
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