Expands a term. The most common use is to expand a grammar rule into a clause. Users may override the default Logtalk grammar rule translator by defining clauses for the predicate <ahref="term_expansion2.html"><code>term_expansion/2</code></a>.
The expansion works as follows: if the first argument is a variable, then it is unified with the second argument; if the first argument is not a variable and clauses for the <code>term_expansion/2</code> predicate are within scope, then this predicate is called to provide an expansion that is then unified with the second argument; if the <code>term_expansion/2</code> predicate is not used and the first argument is a compound term with functor <code>-->/2</code> then the default Logtalk grammar rule translator is used, with the resulting clause being unified with the second argument; when the translator is not used, the two arguments are unified.
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This built-in method may be used to expand a grammar rule into a clause for use with the built-in database methods.
