diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 44 |
1 files changed, 25 insertions, 19 deletions
@@ -7141,16 +7141,27 @@ can be expressed as: .TP Syntax: - (apply <function> <argsequence>) + (apply <function> [ {<arg>}* <trailing-args> ]) .TP Description: -The apply function converts a sequence of values <argsequence> into individual -arguments which are passed to <function>. The return value of the apply -invocation is that of <function>. +The apply function invokes <function>, optionally passing to it an argument +list. The return value of the apply call is that of <function>. -<argsequence> must be list, vector or string. +If no arguments are present after <function>, then <function> is invoked +without arguments. + +If one argument is present after <function>, then it is interpreted as +<trailing-args>. If this is a sequence (a list, vector or string), +then the elements of the sequence are passed as individual arguments to +<function>. If <trailing-args> is not a sequence, then the function is invoked +with an improper argument list, terminated by the <trailing-args> atom. + +If two or more arguments are present after <function>, then the last of +these arguments is interpreted as <trailing-args>. The previous arguments +represent leading arguments which are applied to <function>, prior to the +arguments taken from <trailing-args>. .TP Examples: @@ -7158,11 +7169,17 @@ Examples: ;; '(1 2 3) becomes arguments to list, thus (list 1 2 3). (apply (fun list) '(1 2 3)) -> (1 2 3) + ;; this effectively invokes (list 1 2 3 4) + (apply (fun list) 1 2 '(3 4)) -> (1 2 3) + + ;; this effectively invokes (list 1 2 . 3) + (apply (fun list) 1 2 3)) -> (1 2 . 3) + ;; "abc" is separated into characters which become arguments of list (apply (fun list) "abc") -> (#\ea #\eb #\ec) .TP -Dialect Note 1: +Dialect Note: Note that some uses of this function that are necessary in other Lisp dialects are not necessary in TXR Lisp. The reason is that in TXR Lisp, improper list @@ -7173,19 +7190,8 @@ syntax is accepted as a compound form, and performs application: Here, the variables a and b supply the first two arguments for foo. In the dotted position, x must evaluate to a list or vector. The list or vector's elements are pulled out and treated as additional arguments for foo. - -.TP -Dialect Note 2: - -TXR Lisp apply does not take additional arguments before the list. -In Common Lisp we can write (apply #'list 1 2 (list 3 4 5)) which -yields (1 2 3 4 5). -In TXR Lisp, - -In TXR Lisp, this usage can be simulated using the approach in the -previous Dialect Note 1, or by using code such as: -(apply (fun list) (list 1 2 (list 3 4 5))) or -(apply (fun list) '(,1 ,2 ,*(list 3 4 5))) . +Of course, this syntax can only be used if x is a symbolic form or an atom. It +cannot be a compound form. .SS Functions reduce-left and reduce-right |