Pattern matching binaries.

[Mason Staugler]

In this post there's an example of pattern matching with binaries, but this is what I'm getting now.

(defun foo
  ([(binary 40 (binary rest))]
    rest)
  ([_]
    'unmatched))
> (foo #B("(hello"))
exception error: #(undefined_bittype rest)

Ultimately, I'm looking for the binary equivalent of:

> (defun bar
    ([(list* #\f #\o #\o rest)]
      rest)
    ([_]
      'unmatched))
bar
> (bar "foobar")
"bar"

[Robert Virding]

Hi Mason,

That is my fault as the pattern is wrong. A binary constructor/patten consists of a sequence of segments where each segment has the form (val <specs> ...). A spec is either type (integer,binary,bitstring,float), (size n), big|little-endian, signed|unsigned. The default type is integer. So the pattern should have read (binary 40 (rest binary)) and the function

(defun foo
 ([(binary 40 (rest binary))] rest)
 ([_] 'unmatched))

Sorry about that. A description binaries is at about 2/3 of the file doc/user_guide.txt or in http://docs.lfe.io/user-guide/diving/3.html .

Robert

[Mason Staugler]

That makes sense. Thanks, Robert!