3 Pattern Matching

3.1 Pattern Matching

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

In a pattern matching, a lefthand side pattern is matched against a righthand side term. If the matching succeeds, any unbound variables in the pattern become bound. If the matching fails, a run-time error occurs.

Examples:

1> X.
** 1: variable 'X' is unbound **
2> X = 2.
2
3> X + 1.
3
4> {X, Y} = {1, 2}.
** exited: {{badmatch,{1,2}},...} **
5> {X, Y} = {2, 3}.
{2,3}
6> Y.
3