if CountUnitsInGroup(g)>0 then

function CountUnitsInGroup takes group g returns integer
    local boolean wantDestroy = bj_wantDestroyGroup
    set bj_wantDestroyGroup = false
    set bj_groupCountUnits = 0
    call ForGroup(g, function CountUnitsInGroupEnum)
    if (wantDestroy) then
        call DestroyGroup(g)
    endif
    return bj_groupCountUnits
endfunction

function CountUnitsInGroupEnum takes nothing returns nothing
    set bj_groupCountUnits = bj_groupCountUnits + 1
endfunction

set d = RandomDestructableInRectBJ(r, Condition(function FilterDestr))

function RandomDestructableInRectBJ takes rect r, boolexpr filter returns destructable
    set bj_destRandomConsidered = 0
    set bj_destRandomCurrentPick = null
    call EnumDestructablesInRect(r, filter, function RandomDestructableInRectBJEnum)
    call DestroyBoolExpr(filter)
    return bj_destRandomCurrentPick
endfunction

function RandomDestructableInRectBJEnum takes nothing returns nothing
    set bj_destRandomConsidered = bj_destRandomConsidered + 1
    if (GetRandomInt(1,bj_destRandomConsidered) == 1) then
        set bj_destRandomCurrentPick = GetEnumDestructable()
    endif
endfunction