Editing Pattern matching (section)

====Declarative programming====
In symbolic programming languages, it is easy to have patterns as arguments to functions or as elements of data structures. A consequence of this is the ability to use patterns to declaratively make statements about pieces of data and to flexibly instruct functions how to operate.

For instance, the [[Mathematica]] function <code>Compile</code> can be used to make more efficient versions of the code. In the following example the details do not particularly matter; what matters is that the subexpression <code>{{com[_],  Integer}}</code> instructs <code>Compile</code> that expressions of the form <code>com[_]</code> can be assumed to be [[integer]]s for the purposes of compilation:

<syntaxhighlight lang="mathematica">
com[i_] := Binomial[2i, i]
Compile[{x, {i, _Integer}}, x^com[i], {{com[_],  Integer}}]
</syntaxhighlight>

Mailboxes in [[Erlang (programming language)|Erlang]] also work this way.

The [[Curry–Howard correspondence]] between proofs and programs relates [[ML (programming language)|ML]]-style pattern matching to [[Proof by cases|case analysis]] and [[proof by exhaustion]].