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1 Llama — 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'.
Consider enabling `llama-fontify-mode' to highlight `##' and its
special arguments.
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