Byte-compiled functions have a special data type: they are byte-code function objects. Whenever such an object appears as a function to be called, Emacs uses the byte-code interpreter to execute the byte-code.
Internally, a byte-code function object is much like a vector; its
elements can be accessed using
aref. Its printed
representation is like that for a vector, with an additional ‘#’
before the opening ‘[’. It must have at least four elements;
there is no maximum number, but only the first six elements have any
normal use. They are:
&rest, then bit 7 is set; otherwise it's cleared.
If argdesc is a list, the arguments will be dynamically bound
before executing the byte code. If argdesc is an integer, the
arguments will be instead pushed onto the stack of the byte-code
interpreter, before executing the code.
nil. The value may be a number or a list, in case the documentation string is stored in a file. Use the function
documentationto get the real documentation string (see Accessing Documentation).
nilfor a function that isn't interactive.
Here's an example of a byte-code function object, in printed
representation. It is the definition of the command
#[256 "\211\204^G^@\300\262^A\301^A[!\207" [1 forward-sexp] 3 1793299 "^p"]
The primitive way to create a byte-code object is with
This function constructs and returns a byte-code function object with elements as its elements.
You should not try to come up with the elements for a byte-code function yourself, because if they are inconsistent, Emacs may crash when you call the function. Always leave it to the byte compiler to create these objects; it makes the elements consistent (we hope).