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desc
@@
1.17
log
@Description updated
@
text
@
post-N288 call_nth/2
This draft is part of the Prolog
prologue.
References refer to 13211-1:1995. Parts needing improvements
are underlined.
p.p.9 call_nth/2
p.p.9.1 Description
call_nth(G_0, Nth) is true iff call(G_0) is
true and N being the number of re-executions
of call(G_0), Nth unifies with the integer N+1.
Procedurally, call_nth(G_0, Nth) is executed as
follows:
a) Creates a counter N with value zero,
b) If Nth is an integer smaller or equal N,
the goal fails,
or b') If there is no value greater N that is unifiable
with Nth, the goal fails,
c) (Re-)executes call(G_0),
d) If it fails, the goal fails,
e) Else if it succeeds, sets N to N+1,
f) Unifies Nth with counter N,
g) If the unification succeeds, the goal succeeds,
h) Else proceeds to p.p.9.1 b,
call_nth(G_0, Nth) is re-executable. On backtracking,
continue at p.p.9.1 g.
p.p.9.2 Template and modes
call_nth(?term, ?integer)
p.p.9.3 Errors
a) G_0 is a variable and Nth is not zero —
instantiation_error.
b) G_0 is neither a variable nor a callable term
and Nth is not zero —
type_error(callable, G_0).
c) Nth is neither a variable nor an integer —
type_error(integer, Nth).
d) Nth is an integer less than zero —
domain_error(not_less_than_zero, Nth).
e) The value of flag bounded is true and
at step p.p.9.1 e N+1 is larger
than max_integer — evaluation_error(int_overflow). —representation_error(max_integer).
2008-01-27 First definition for SWI 2012-07-09 Implementations for SWI, SICStus, YAP, ECLiPSe.
2017-10-21 Added to SWI
2020-08-22 Added to Scryer library
2020-09-01 Added to Trealla
2022-04-24 Added to Ichiban
2022-06-06 Added to Prolog prologue
2023-06-25 Added to GNU Prolog 2023-07-03 Added to YAP
Validated HTML
@
1.16
log
@+YAP
@
text
@d83 2
a84 2
true and Nth unifies with the integer being the
N+1st re-execution of call(G_0).
@
1.15
log
@*** empty log message ***
@
text
@d199 3
d214 1
@
1.14
log
@*** empty log message ***
@
text
@d196 3
@
1.13
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@Cleanup from previous alternative
@
text
@d206 2
@
1.12
log
@*** empty log message ***
@
text
@d189 1
a189 1
false. % or type_error(callable,1)
d192 1
a192 1
false. % or instantiation_error
@
1.11
log
@post, example added
@
text
@d71 1
a71 1
This draft is proposed for consideration of WG17 for its inclusion into the Prolog
d77 1
a77 1