Exercise 1.42: Let 
  f
 and 
  g
 be two
one-argument functions.  The 
composition 
  f
 after 
  g
 is defined
to be the function 
  
    x
    ↦
    f
    (
    g
    (
    x
    )
    )
  
.  Define a procedure
compose that implements composition.  For example, if inc is a
procedure that adds 1 to its argument,


((compose square inc) 6)
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