Have you seen the update in my reply?

Floats are automatically adjusted to avoid leading zeros in the mantissa.

update

Think float, this

x1   = 256080
x2   = 258160
diff = 2080.00000000003

[download]

really just means (in slightly inaccurate decimal interpretation)

x1   = 2.56080            e5
x2   = 2.5816000000000003 e5  (error ignored when printed)
diff = 2.08000000000003   e3  (error visible when printed)

[download]

As you can see the error (here decimal 3) is shifted to the left and out of error margin into printed "visibility".

update

after firing up my laptop, here a proof of concept

  DB<115> $x1 = 2.56080e5
 => 256080

  DB<116> $x2 = 2.5816000000000003e5 
 => 258160                 # within error margin, ignored in normal di
+splay

  DB<117> printf '%.11f', $x2               
258160.00000000003         # forced into visibility, hence $x2 NOT an 
+integer

  DB<118> $x2-$x1
 => 2080.00000000003       # error can't be ignored any more

[download]

Cheers Rolf
(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!

In reply to Re^3: Integers sometimes turn into Reals after substraction (printed accuracy and float subtraction) by LanX
in thread Integers sometimes turn into Reals after substraction by rduke15

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