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Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 28 |
1 files changed, 18 insertions, 10 deletions
@@ -9,31 +9,39 @@ to a `lambda` expressions, which wraps around its arguments. This `lambda` expression calls the function FN with arguments ARGS and returns its value. Its own arguments are derived from -symbols found in ARGS. Each symbol from `%1` through `%9`, which -appears in ARGS, is treated as a positional argument. Missing -arguments are named `_%N`, which keeps the byte-compiler quiet. -In place of `%1` the shorthand `%` can be used, but only one of -these two can appear in ARGS. `%*` represents extra `&rest` -arguments. +symbols found in ARGS. + +Each symbol from `%1` through `%9`, which appears in ARGS, +specifies an argument. Each symbol from `&1` through `&9`, which +appears in ARGS, specifies an optional argument. All arguments +following an optional argument have to be optional as well, thus +their names have to begin with `&`. Symbol `&*` specifies extra +(`&rest`) arguments. + +Instead of `%1`, the shorthand `%` can be used; but that should +only be done if it is the only argument, and using both `%1` and +`%` is not allowed. Likewise `&` can be substituted for `&1`. +Finally, for backward compatibility, `%*` can be used in place +of `&*`, but only if there are no optional arguments. Instead of: ```elisp -(lambda (a _ c &rest d) +(lambda (a _ &optional c &rest d) (foo a (bar c) d)) ``` you can use this macro and write: ```elisp -(##foo % (bar %3) %*) +(##foo %1 (bar &3) &*) ``` which expands to: ```elisp -(lambda (% _%2 %3 &rest %*) - (foo % (bar %3) %*)) +(lambda (%1 _%2 &optional &3 &rest %*) + (foo %1 (bar &3) %*)) ``` The name `##` was choosen because that allows (optionally) |