functional.txt
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Sets
 Collections without order and repetition
 We just want to record whether some element is present (at least once, anywhere)
 Example: testing for legal file names (drawn from a limited character set)
 See set.py


















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Map and Filter

 Compare map and filter patterns, comprehensions vs. built-in functions
 Comprehensions are more versatile, Pythonic
 Functions support functional programming style, like Lisp, Haskell, F#, ...


















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Conditional expressions

 Comprehensions can only contain expressions, not statements - how to handle 'if' ?
 If statement: if p: x = v1 
               else: x = v2
 Conditional expression (on right-hand-side): x = v1 if p else v2
  can use conditional expression WITHOUT assignment: v1 if p else v2
 Another example of statement vs. expression, mutation vs. functional style















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Reductions

 See product.py
 Built-in reductions: sum, max, min, all, any
 reduce function: motivate operator module and lambda expressions
 operator module makes operators available as named function where syntax requires
  use operator.mul instead of * etc.
  alternatively, can use lambda expression - compare to product2 named function
 lambda is used heavily with map and filter - but not needed with comprehensions