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Comment by lukasb | Hacker News Reader

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lukasb·

Why

foo(X) -> foo1(X).

foo1(bar) -> void; foo1(_Else) -> undefined.

rather than just

foo(bar) -> void; foo (_Else) -> undefined.

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It is just a simple example to convey that a portion of foo/1 contains a case statement, and that case statement is being replaced with a function. There could be more lines in foo/1. The point is that both the case statement and the multi-clause function are identical in behavior, but the function prevents nesting at the call site.

To illustrate a point of how the two are equivalent and one could almost write an automatic translator. But yeah it ended up confusing many here.

Also the _Else part I would just make it into foo(_) -> undefined.

foo(_Else). -> undefined. Doesn't seem very erlangy. I'd expect a runtime error, as someone's passed foo() the wrong value.

But in the given example, isn't foo(_Else) = foo1(_Else) = undefined anyways?

> Doesn't seem very erlangy. I'd expect a runtime error, as someone's passed foo() the wrong value.

It depends.

Sometimes you want to crash when handed an unexpected value.

Sometimes you expect that you'll be handed unexpected values and need to either fail more gracefully, print a warning and then fail, or warn and keep going, or whatever.

Erlang gives you a bunch of tools, and they all have their place. [0] :)

[0] With the possible exception of the if statement... which is of questionable utility.

The "if" keyword should have been "when" instead. It's useful in some cases, but rarely used.

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