Mercury (programming language): Difference between revisions

Revision as of 06:10, 3 May 2020

Revision as of 18:07, 11 May 2020

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== Examples ==

[[Hello world program|Hello World]]:

<sourcesyntaxhighlight lang="prolog">

:- module hello.

:- interface.

Line 108:

main(!IO) :-

io.write_string("Hello, World!\n", !IO).

</syntaxhighlight>

</source>

Calculating the 10th [[Fibonacci number]] (in the most obvious way):<ref name="tutorial">Adapted from [http://www.mercurylang.org/documentation/papers/book.pdf Ralph Becket's Mercury tutorial]</ref>

<sourcesyntaxhighlight lang="prolog">

:- module fib.

:- interface.

Line 128:

io.nl(!IO).

% Could instead use io.format("fib(10) = %d\n", [i(fib(10))], !IO).

</syntaxhighlight>

</source>

<code>!IO</code> is a "state variable", which is [[syntactic sugar]] for a pair of variables which are assigned concrete names at compilation; for example, the above is desugared to something like:

<sourcesyntaxhighlight lang="prolog">

main(IO0, IO) :-

io.write_string("fib(10) = ", IO0, IO1),

io.write_int(fib(10), IO1, IO2),

io.nl(IO2, IO).

</syntaxhighlight>

</source>

==Release schedule==