erlang-notes
by earl, 6444 days ago
- variables are Uppercased (e.g. X, Y, Foobar, Point)- atoms (literal symbols) are lowercased (e.g. x, y, foobar, point)
- atoms may be enclosed in '...' (e.g. 'I am an atom', '+'); note that 'a' == a
- {...} is for tuples, components are seperated via , (e.g. {point, {x, 42}, {y, 10}}
- [...] is for lists, elements are seperated via , (e.g. [1, 2, 3, 4])
- strings ("...") are shorthand for lists of latin1 character codes
- $c is for characters; so "foo" == [$f,$o,$o] == [102,111,111]
- <<...>> is literal binary data (aka bit syntax)
- = does pattern matching: lhs is matched against rhs (one-sided unification); so lhs may contain variables, rhs must not. return value of a successful match is rhs
- _ is a wildcard pattern
- [H|T] matches H against a list's head, and T against its tail. matching multiple leading elements is possible: [X1,X2,X3|XS]. note that [X|[Y|[Z|T]]] equals [X,Y,Z|T] and [X|[Y|[]]] equals [X,Y].
- pattern=Name binds a (sub-)pattern to a name (e.g. {point, {x, 42}=X, _} binds X to {x,42} -- analog to haskell's @)
- list comprehension: [ F(X) || X <- L ]
- reifying a function: fun Module:FuncName/Arity (e.g. lists:map(fun tuple_to_list/1, [{a,b},{c,d}]))
- anonymous function abstraction: fun(X,Y,Z) -> ... end. E.g.:
1> lists:map(fun(X) -> 2 * X end, [1,2,3,4]).
[2,4,6,8]
2> lists:foreach(fun(X) -> io:format("~p~n", [X]) end, [1,2,3,4]).
1
2
3
4
ok
- erl shell:
help(): gives a help of all shell functions
b(): displays all vairable bindings
f(): unbinds all variables
f(X): unbinds variable X
c(File): compiles and loads code in File
regs(): information about registered processes
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