Why would you make your code so complicated?
I would simply write:
T ==> Integer
pwrset(s: List T) : List List T ==
empty? s => [[]]
ps: List List T := pwrset rest s
t: T := first s
tps := [cons(t, p) for p in ps]
concat(ps, tps)
powerSet(l: List T): List List T == sort((x,y)+->#x<#y, pwrset sort l)
On 4/7/25 17:14, Martin Baker wrote:
localPowerSets(j:List(S),filter:List(S)->Boolean): List(List S) ==
empty? j => list []
Sm := localPowerSets(rest j,filter)
Sn: List List S := []
for x in Sm repeat
if filter(x) then
Sn := cons(reverse cons(first j, x),Sn)
append(Sn, Sm)
Why do you use "reverse" here?
Can you tell a reason for this filter function?
gradeAndOrder(a:List S,b:List S) : Boolean ==
if #a < #b then return true
if #a > #b then return false
for ia in a for ib in b repeat
if S has OrderedSet then
if ia < ib then return true
if ia > ib then return false
false
powerSetFiltered(j:List(S),filter:List(S)->Boolean):List List S ==
map(reverse,sort(gradeAndOrder,localPowerSets(j,filter)))
Again, why reverse?
powerSet(j:List(S)):List List S ==
powerSetFiltered(j,(x)+-> true)
If you want this "stand-alone" then you have to write a package with
parameter T around the above code.
Ralf
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