Missing rounding in float/1 for bigint argument about trealla HOT 12 CLOSED

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Yes it seems so:

?- Z is float(51^10), T is Z-1.1904242382761301E17.
   Z = 1.19042423827613e+17, T = 0.0

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Can you show a Prolog query where this happens?
Also its not necessarily a display problem. For example
many Math.pow(double,double) implementations cannot

do the problem correctly. They cannot or do not round to
the theoretical optimum, they have inherently a higher error
than only one Unit in the last place (ULP). So a certain error

is to expect. You see this here:

/* Dogelog Player, JavaScript */
?- X is 51**10.
X = 1.19042423827613E17.

?- X is float(51^10).
X = 119042423827613010.0.

In the above the (**)/2 is Math.pow(double,double) and the
(^)/2 is exact bigint exponentiation. I took the pair (51,10)
from a list of pairs where (**)/2 and (^)/2 often disagree

based on Math.pow(double,double) typically being weak.

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I have opened a separate ticket for printing. Because
this can get extremly confusing, if printing is not precise
enough. The ticket is here:

not precise enough float printing
#49

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printing needs to satisfy. If this is not satisfied, its
very hard to debug other errors, it will "mask" other
errors, like erros or variations in arithmetic such

as (/)/2, (**)/2, (^)/2 and float/2:

read(write(X))) == X

in the 3.0 example its clear. In SWI-Prolog the result is
different. Try subtracting 3 from the division? The 1/10
example, I don't know, maybe better discuss it here:

not precise enough float printing
#49

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Here you see SWI-Prolog computes another number,
the issue is currently discussed in SWI-Prolog forum.
They use mqr_get_d instead mqr_get_d_nearest or

somesuch is their problem. Also their a varying approachs to
realize (/)/2, either with divmod(A,B,...) or simply
(float)A/(float)B. Their system might also differ in this respect:

/* Trella Prolog */
?- N9 is 370370367037037036703703703670 / 123456789012345678901234567890 - 3.
   N9 = 4.440892098500626e-16.

/* SWI-Prolog */
?- N9 is 370370367037037036703703703670 / 123456789012345678901234567890 - 3.
N9 = 0.

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The (^)/2 error is gone, I now find:

Trealla Prolog (c) Infradig 2020-2022, v2.7.15
?- X is 51^10.
   X = 119042423827613001

And the rest is a printing artefact, as already observed:

?- X is 51^10, Z is float(X), Z =:= 1.19042423827613008E17.
   X = 119042423827613001, Z = 1.19042423827613e+17.

Closing this ticket.

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