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    <p>That's a list of <em>atoms</em>, not strings. Strings in Prolog are usually <em>list of character codes</em>, expressed like </p> <pre><code>["f(a,45)", "f(b,13)", "f(c,12)"] </code></pre> <p>Anyway, apply a conversion to each element with a recursive function:</p> <pre><code>convert([], []). convert([Atom|Atoms], [Pair|Pairs]) :- convert_element(Atom, Pair), convert(Atoms, Pairs). </code></pre> <p>Instead of recursion you could use <a href="http://www.swi-prolog.org/pldoc/doc_for?object=section%282,%27A.2%27,swi%28%27/doc/Manual/apply.html%27%29%29" rel="nofollow">maplist</a>/3 in this way:</p> <pre><code>convert(As, Ps) :- maplist(convert_element, As, Ps). </code></pre> <p>To convert an element, you need a parser. DCGs are convenient:</p> <pre><code>convert_element(Atom, [N, A]) :- atom_codes(Atom, Codes), phrase(("f(", atomc(Ac), ",", numc(Nc), ")"), Codes, []), atom_codes(A, Ac), number_codes(N, Nc). atomc(A) --&gt; ([C], {is_lowerc(C)}, atomc(Cs), {A = [C|Cs]}) ; {A = []}. numc(N) --&gt; ([C], {is_numc(C)}, numc(Cs), {N = [C|Cs]}) ; {N = []}. is_lowerc(C) :- C @&gt;= 0'a, C @=&lt; 0'z. is_numc(C) :- C @&gt;= 0'0, C @=&lt; 0'9. </code></pre> <p>test:</p> <pre><code>?- convert(['f(a,45)', 'f(b,13)', 'f(c,12)'],L). L = [[45, a], [13, b], [12, c]] . </code></pre> <p>atomc//1 &amp; numc//1 are expressed in a compact way, but are very simple recursive pattern matching procedures, i.e. atomc//1 could be</p> <pre><code>atomc([C|Cs]) --&gt; [C], {is_lowerc(C)}, !, atomc(Cs). atomc([]) --&gt; []. </code></pre>
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    1. COOne little question can you explain (or give a link to good tutorial about that) how this statemat works? atomc(A) --> ([C], {is_lowerc(C)}, atomc(Cs), {A = [C|Cs]}) ; {A = []}. I'm just not familiar wiht using ; and --> in prolog
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      1. USAdrian Modliszewski
    2. CO`-->` it's the DCG operator, while `;` it's the usual alternative (disjuntion) operator. DCGs are just a minimal layer on pure Prolog, usually implemented by translation, adding 2 argument to rules to implement `difference lists`. The resulting top down parser it's very expressive, mainly because rules can have as many arguments as needed. That make easy to add semantic to the grammar. I've searched a tutorial, found [this](http://www.csupomona.edu/~jrfisher/www/prolog_tutorial/7_2.html). At first glance seems useful...
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    3. COThanks, you helped me very, very much!
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