diff options
| -rw-r--r-- | txr.1 | 50 |
1 files changed, 29 insertions, 21 deletions
@@ -10034,28 +10034,15 @@ namely that the meta-numbers and meta-symbols of the .code op operator can be used in the dot position). -The value of the expression in the dot position is converted to a list, if it -is a sequence. Otherwise if it is an non-sequence atom, no conversion is -applied. In either case, the resulting list's elements constitute -additional arguments to the function. +If the dot position of a compound form is an atom, then the following +equivalence applies: -If the value emerging from the dot position is an atom (referred to as -the "sole atom" below) other than -.codn nil , -or an improper list (a list ending in a terminating atom -other than -.codn nil ), -then the function being invoked must be a variadic function, otherwise -the call is erroneous. Furthermore, all required argument positions of a -function must be filled before encountering the sole atom or terminating -atom: such an atom doesn't count as an argument, whether or not it is -.codn nil , -and indicates that no more arguments follow. -Only the trailing list argument of a variadic function (denoted in the -.code lambda -operator's syntax as the optional -.metn rest-param ) -may take a sole atom or terminating atom as a value. +.cblk + (f a b c ... . x) <--> (apply (fun f) a b c ... x) +.cble + +Effectively, the dot notation constitutes a shorthand for +.codn apply . The DWIM brackets are similar, except that the first position is an arbitrary expression which is evaluated according to the same rules as the remaining @@ -22986,6 +22973,27 @@ The previous arguments represent leading arguments which are applied to prior to the arguments taken from .metn trailing-args . +Note that if +.meta trailing-args +value is an atom or an improper list, the function is then +invoked with an improper argument list. Only a variadic +function may be invoked with an improper argument lists. +Moreover, all of the function's required and optional +parameters must be satisfied by elements of the +improper list, such that the terminating atom either +matches the +.meta rest-param +directly (see the +.code lambda +operator) or else the +.meta rest-param +receives an improper list terminated by that atom. +To treat the terminating atom of an improper list as an +ordinary element which can satisfy a required or optional +function parameter, the +.code iapply +function may be used, described next. + The .code iapply function ("improper apply") is similar to |