-- Following are several valid expressions.
-- They produce a result and hence they should return expected results
[]
2:[]
2:[3]
2:[3,4]
True:[]
True:[False]
head [2,3,4]
tail [2,3,4]
map not [True,False,True]
[2,3]++[4,5]
take 2 [2,3,4,5]
take 7 [2,3,4,5]

-- Following are several valid expressions.
-- however their evaluation must fail and hence it should not produce any output
-- Here we are testing for failure !
head []
tail []

-- Need tests for the following standard list operators
-- !!, length, null, reverse, concat, drop, and, or, elem, nub, delete