option.ps

%%% Some: [v]
%%% None: []

/some {                             % v
    [ exch ]                        % [v]
} def

/none {
    []
} def 

/map {                              % A {op} %%% {op} is operation to be called for each element in A
    [ 3 1 roll                      % [ A {op}
    exch                            % [ {op} A
    {                               % [ {op} e
        1 index                     % [ {op} e {op}
        exec                        % [ {op} r %%% r is result of executing {op} on e
        exch                        % [ r {op}
    } forall                        % [ ... {op}
    pop                             % [ ...
    ]                               % [ r1 r2 ... ] => [ r1 r2 ... ]
} def

/flatten {                          % A[B] %%% A is an array containing arrays.
    [ exch                          % A[B] | 
    {                               % B | 
        {} forall                   % ... |
    } forall                        % ... |
    ]                               % [ ... ]
} def 

/flatmap {
    map flatten
} def