Pattern Matching

Pattern Matching

Variables are bound to values through the pattern matching mechanism. Pattern matching occurs when evaluating the case, receive, try, and the match operator (=) expressions.

In pattern matching, a left-hand side pattern is matched against a right-hand side term. If the matching succeeds, any unbound variables in the pattern become bound. If the matching fails, an exception is raised.

Examples:

1> X.
** 1:1: variable 'X' is unbound **
2> X = 2.
2
3> X + 1.
3
4> {X, Y} = {1, 2}.
** exception error: no match of right hand side value {1,2}
5> {X, Y} = {2, 3}.
{2,3}
6> Y.
3