Re: Nested list comprehension

[whospal]

Some more codes...
    
    
    # Python codes:
    unitlist = ([cross(rows, c) for c in cols] +
        [cross(r, cols) for r in rows] +
        [cross(rs, cs) for rs in ('ABC','DEF','GHI') for cs in 
('123','456','789')])
    
    units = dict((s, [u for u in unitlist if s in u])
        for s in squares)
    
    peers = dict((s, set(sum(units[s],[]))-set([s]))
        for s in squares)
    
    
    Run

I tried with... 
    
    
     # Nim codes:
    var unitlist: seq[string] =
        [for c in cols: cross(rows, cast[string](c))] +
            [for r in rows: cross(r, cols)] +
                [for rs in ("ABC","DEF","GHI"):
                    for cs in ("123","456","789"):
                        cross(rs, cs)]
    
    var units = initTable[string](4):
        for s in squares:
            for u in unitlist:
                if s in u:
                    {s, u}
    
    var peers = initTable[string](4):
        for s in squares:
            {s, toHashSet(sum(units[s],[]))-toHashSet([s])
    
    
    Run

But encountered lots of exceptions... :(

The documentation of Seq & Tables are very poor in Nim. Not many examples to 
learn from.

Please help!