systemdict begin

/setpacking {pop} ?def
/currentpacking false ?def

%
% A "cond" (condition) statement: Consists of predicate-proc pairs.
% The first predicate that evaluates to true executes its correnponding
% procedure.  Thus:
%
%    2 {
%        {dup 1 eq}	{(one)}
%        {dup 2 eq}	{(two)}
%        true		{(other)}
%    } cond
%
% results in "2 (two)" being left on the stack.  Note "true" effects
% a default branch.
%
% The implementation is very wierd.  Here are the author's notes:
% Here's another entry in the cond-test.  It's like Owen & Jerry's last
% ones in that it uses forall to step through all the elements, except
% instead of leaving a boolean or integer on the top of the stack to tell
% it what to do on the next iteration, it puts the code to be executed
% itself.  Notice the mind-bending self referentiality:
% 
% NextProc contains the code to be executed the next time a test is to be
% made, "exec null exit" gets executed in the clause after a true result,
% "pop /NextProc" gets executed in the clause after a false result -
% which is setting up for the next test.
%
% The "/NextProc" in the definition of /NextProc should really be
% //NextProc except that NextProc isn't defined yet...
% I then reach into the array and install it after /NextProc
% is defined.
% 
currentpacking	    	% bool left on stack for later setpacking call
false setpacking
/NextProc { exec { { exec null exit } } { { pop /NextProc } } ifelse } def
//NextProc 2 get 0 get 1 //NextProc put % replace placeholder by a recursion
setpacking

/cond { % args array => args
    //NextProc			% args a nextproc
    exch {			% args nextproc ai
	exch exec		% args newnextproc
    } forall
    pop
} ?def
currentdict /NextProc undef

end % systemdict