Programming Elixir

Function Calls and Pattern Matching

In the previous chapter we covered how anonymous functions use pattern matching to bind their parameter list to the passed arguments. The same is true of named functions. The difference is that we write the function multiple times, each time with its own parameter list and body. Although this looks like multiple function definitions, purists will tell you it’s multiple clauses of the same definition (and they’d be right).

When you call a named function, Elixir tries to match your arguments with the parameter list of the first definition (clause). If it cannot match them, it tries the next definition of the same function (remember, this must have the same arity) and checks to see if it matches. It continues ...