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# ack

This folder contains an implementation of the Ackermann function (general
recursive function). For a description of this function see e.g.

https://en.wikipedia.org/wiki/Ackermann_function

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

```logtalk
%versions
```

Start by loading the example:

```logtalk
logtalk_load(ack(loader)).
```

Sample queries:

```logtalk
ack::ack(2, 4, V).
```

<!--
V = 11.
-->

```logtalk
ack::ack(3, 3, V).
```

<!--
V = 61.
-->

```logtalk
ack::ack(3, 4, V).
```

<!--
V = 125.
-->

Sample queries for backends implementing the `time/1` predicate. E.g.,
SWI-Prolog, Trealla Prolog, XVM, or YAP. The adapter files for SWI-Prolog
and YAP ensure that a `(::)/2` goal in the argument of the `time/1`
meta-predicate is compiled prior to calling it:

```logtalk
% auto-load the predicate in the case of SWI-Prolog
time(true).
```

<!--
true.
-->

```logtalk
time(ack::ack(2, 4, V)).
```

<!--
% 98 inferences, 0.00 CPU in 0.00 seconds (0% CPU, Infinite Lips)
V = 11.
-->

```logtalk
time(ack::ack(3, 3, V)).
```

<!--
% 2,451 inferences, 0.00 CPU in 0.00 seconds (0% CPU, Infinite Lips)
V = 61.
-->

```logtalk
time(ack::ack(3, 4, V)).
```

<!--
% 10,326 inferences, 0.00 CPU in 0.00 seconds (0% CPU, Infinite Lips)
V = 125.
-->
