[fpc-pascal] fpc 32 / 64 bit / c++/ floating point question

[Marco van de Voort]

In our previous episode, Vinzent H?fler said:
> <mueller_michael at alice-dsl.net> wrote:
> 
> > Single has 7 significant digits.
> 
> <mode style="nitpicking">
> Six significant digits. The seventh already is unreliable.
> </mode>

A mistake in the nth digit can show up much higher than the nth or n-1th
digit, depending on the magnitude of the condition number.  

A commonly known case of an error in inputs propagating to large errors in
output is catastrophic cancellation, which can cause a
condition number >>1.  And the example _does_ add negative values to
positive ones, which is equal to the subtraction in catastrophic
canellation.