ahoy matey

stevan apter — 2004-10-23 22:16:13

easier to show the problem than explain it:



a list which contains nested occurrences of mated elements.  

in this case, the list is a string and the mated elements

are '( and '):



  "(abc(def)(ghi)(jk(lmn)(op)))rstuvw"



a list of the mates:



  "()"



split the list into a pair of lists:  the first of the pair

is everything up to the first right-mate which balances, and

the second is everything from there on:



  "(abc(def)(ghi)(jk(lmn)(op)))rstuvw" "()" mated

["(abc(def)(ghi)(jk(lmn)(op)))" "rstuvw"]



  "(ghi)(jk(lmn)(op)))rstuvw" "()" mated

["(ghi)" "(jk(lmn)(op)))rstuvw"]



  "(abc(def)(ghi)(jk(" "()" mated

["(abc(def)(ghi)(jk(" ""]



in k:



  mated:{(0,((#x)&1+(-/+\'x~'/:y)?0))_ x}



  s:"(abc(def)(ghi)(jk(lmn)(op)))rstuvw"

  mated[s;"()"]

("(abc(def)(ghi)(jk(lmn)(op)))"

 "rstuvw")



transcribed into XY:



; mated   [dup] dip mate 0 ,. _. ;

; mate    [dup] dip [mate.] each/ i - 0 ? 1 + [#:] dip & ;

; mate.   [~] each\ ,: 0 [+] under! ;



to construct the revised conditional i described to daniel,

one would say something like



    queue [if: fi:] mated



to split the queue.