[erlang-questions] Keyword documentation
Fri Feb 19 19:12:25 CET 2010
Start a block, used for grouping expresssions (no idea what use it is)
Most common uses I've found are in list comprehensions:
[ X || X <- List, begin FooVal = foo(X), ... complex test using
FooVal more than once ... end ].
FooVal = foo(X),
... complex expression using FooVal more than once ...
end || X <- List ].
It lets you introduce temporary variables in places where the context
makes it difficult to reference them.
I do this for documentation purposes sometimes (see R.O.K.s previous
objection to F local fun var), and when a call to an expensive
function needs to occur more than once in a decision process.
Also works in binary comprehensions:
<< << X >> || << X >> <= Binary, begin FooVal = foo(X), ... end >>.
<< <<(begin FooVal = foo(X), ... end)>> || << X >> <= Binary >>.
The parens are necessary because the expression in the binary
constructor has to be evaluated and returned as a valid element
before the binary construction can occur.
The value of a begin ... end construct is the value of the last
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