diff options
| -rw-r--r-- | cppawk-cons.1 | 111 | ||||
| -rw-r--r-- | cppawk-include/cons.h | 1 | ||||
| -rw-r--r-- | testcases-cons | 25 |
3 files changed, 137 insertions, 0 deletions
diff --git a/cppawk-cons.1 b/cppawk-cons.1 index 1833c8f..0fa8f7a 100644 --- a/cppawk-cons.1 +++ b/cppawk-cons.1 @@ -118,6 +118,9 @@ cons \- Lisp-like data representation and control flow macros dolisti(\fIitem\fP, \fIindex\fP, \fIlist\fP) \fIstatement\fP + doconses(\fIsuffix\fP, \fIlist\fP) + \fIstatement\fP + \fI// stack-like list manipulation\fP push(\fIy\fP, \fIx\fP) \fI// push item y onto x, updating location x\fP @@ -2022,6 +2025,114 @@ contains boxed values, then those boxed values become fields. print $\fIi\fP .ft R +.SH LIST ITERATION +.bk +.SS Macros \fIdolist\fP, \fIdolisti\fP and \fIdoconses\fP +.bk +Syntax: + +.ft B + dolist(\fIitem\fP, \fIlist\fP) + \fIstatement\fP + + dolisti(\fIitem\fP, \fIindex\fP, \fIlist\fP) + \fIstatement\fP + + doconses(\fIsuffix\fP, \fIlist\fP) + \fIstatement\fP +.ft R + +.B Description + +The +.BR dolist , +.BR dolisti +and +.B doconses +macros provide an iteration construct for traversing lists. + +The +.B dolist +and +.B dolisti +macros require +.I list +to be an expression evaluating to a list. If the iteration is +permitted to traverse the entire list (no early break out of the loop +takes place), then +.I list +must be a proper list. The +.I item +and +.I index +arguments must be identifiers suitable for use as a variable name. +The macro invocations must be immediately followed by a +.IR statement , +which must be syntactically a statement. + +The +.B dolisti +macro evaluates the +.I list +expression and initializes an internal iterator. It then enters +into a loop which visits every element of the list, and for +each element, executes the +.IR statement . +On each iteration, the +.I item +variable is set to the next available element of the list, and +.I index +is set to a successive integer, starting from 0. Thus each +.I item +value is accompanied by an +.I index +value indicating that value's zero-based position in the list. + +The +.B dolist +macro is similar, except it takes no +.I index +argument, and consequently does not provide the index values. + +The +.I item +and +.I index +variables are assigned. If such variables are already visible, those +variables are used. Moreover, after these loops execute, the variables +remain visible, with their most recent values. If it is desirable for these +variables to be local, the program must arrange that in the surrounding code. + +The +.B doconses +macro allows improper lists. It iterates the +.I list +over a +.I statement +exactly like +.B dolist +and +.BR dolisti . +The +.I suffix +argument must be an identifier suitable for use as a variable name, +The +.B doconses +provides access to the conses of the list rather than the items. +On the first iteration, the +.I suffix +variable is first set to the entire list. On the second iteration, +it is set to the rest of the list. Then to the rest of that and +so forth. For instance if the input list is +.B "(1 2 3 . 4)" +then +.I suffix +is stepped over the values +.BR "(1 2 3 . 4)" , +.B "(2 3 . 4)" +and finally the last cons cell +.BR "(3 . 4)" . + .SH "SEE ALSO" cppawk(1), cppawk-fun(1) diff --git a/cppawk-include/cons.h b/cppawk-include/cons.h index 6b7774e..fed6ffb 100644 --- a/cppawk-include/cons.h +++ b/cppawk-include/cons.h @@ -41,6 +41,7 @@ #define pop(list) __pop(list) #define dolist(item, list) __dolist(item, list) #define dolisti(item, index, list) __dolisti(item, index, list) +#define doconses(iter, list) __doconses(iter, list) #define list_begin() __list_begin() #define list_add(stk, item) __list_add(stk, item) #define list_end(stk) __list_end(stk) diff --git a/testcases-cons b/testcases-cons index ec7e6cb..4dc2788 100644 --- a/testcases-cons +++ b/testcases-cons @@ -774,3 +774,28 @@ BEGIN { C1,1:12 foo Tfoo +-- +41: +$cppawk ' +#include <cons.h> + +BEGIN { + dolist (x, list(1, 2, 3)) + print x + print x + dolisti (x, i, list(1, 2, 3)) + print x, i + doconses (s, listar(1, 2, 3, 4)) + print sexp(s) +}' +: +1 +2 +3 +3 +1 0 +2 1 +3 2 +(1 2 3 . 4) +(2 3 . 4) +(3 . 4) |