Homepage: https://github.com/tarsius/llama
Author: Jonas Bernoulli
Updated:
Compact syntax for short lambda
This package implements a macro named `##', which provides a compact way
to write short `lambda' expressions.
The signature of the macro is (## FN &rest BODY) and it expands to a
`lambda' expression, which calls the function FN with the arguments BODY
and returns the value of that. The arguments of the `lambda' expression
are derived from symbols found in BODY.
Each symbol from `%1' through `%9', which appears in an unquoted part
of BODY, specifies a mandatory argument. Each symbol from `&1' through
`&9', which appears in an unquoted part of BODY, specifies an optional
argument. The symbol `&*' specifies extra (`&rest') arguments.
The shorter symbol `%' can be used instead of `%1', but using both in
the same expression is not allowed. Likewise `&' can be used instead
of `&1'. These shorthands are not recognized in function position.
To support binding forms that use a vector as VARLIST (such as `-let'
from the `dash' package), argument symbols are also detected inside of
vectors.
The space between `##' and FN can be omitted because `##' is read-syntax
for the symbol whose name is the empty string. If you prefer you can
place a space there anyway, and if you prefer to not use this somewhat
magical symbol at all, you can instead use the alternative name `llama'.
Instead of:
(lambda (a &optional _ c &rest d)
(foo a (bar c) d))
you can use this macro and write:
(##foo %1 (bar &3) &*)
which expands to:
(lambda (%1 &optional _&2 &3 &rest &*)
(foo %1 (bar &3) &*))
Unused trailing arguments and mandatory unused arguments at the border
between mandatory and optional arguments are also supported:
(##list %1 _%3 &5 _&6)
becomes:
(lambda (%1 _%2 _%3 &optional _&4 &5 _&6)
(list %1 &5))
Note how `_%3' and `_&6' are removed from the body, because their names
begin with an underscore. Also note that `_&4' is optional, unlike the
explicitly specified `_%3'.