Succinctly expressing random number generation in a functional language

random-number-generation.elm

-- Original code to generate random numbers

let (nChars, seed2) = generate (int 3 5) seed1
    (vIndices, seed3) = generate (list nChars (int 0 1000)) seed2
    (cIndices, seed4) = generate (list nChars (int 0 1000)) seed3
    (length, seed5) = generate (int 0 2) seed4
    config = {vIndices = vIndices,
              cIndices = cIndices}

-- Dictionary that represents computation 
-- Same format found in http://dask.pydata.org/en/latest/spec.html

{'nChars':   (int,3,5),
 'vIndices': (list,'nChars',(int,0,1000)),
 'cIndices': (list,'nChars',(int,0,1000)),
 'length':   (int,0,2)}

The key insight from dask is that you can specify the graph of dependencies very simply with a dictionary of tuples.