Erlang Programming/Bitsyntax

Bit Strings

Erlang lets us use Bit Strings. They have the form

<<Value:Bitlength>> or <<v1:length1,v2:length2,...>>

The default bit length is 8.

65> <<1:8>> == <<1>>. 
true

Bit strings are padded on the left.

66> <<1:8>> == <<00000001>>. 
true

Some bit strings have string-like representations.

38> <<00011111>>.
<<"g">>

We can select parts of a bit string with pattern matching.

45> <<H:2,T:6>> = <<"A">>. 
<<"A">>
46> H. 
1
47> T.
1 
86> <<01000001>> == <<"A">>.
true
87> <<1:2,1:6>> == <<"A">>.
true
88> <<65>> == <<"A">>.
true

We can match X to a value.

95> <<1:2,X:6>> = <<"A">>. 
<<"A">>
96> X.
1

But we can not match Y to a bit length.

97> <<1:2,1:Y>> = <<"A">>.
** 1: variable 'Y' is unbound **