Title: WTFunctional: Modifying yout WTF-Count using functional programming
Author: Oliver Rümpelein
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* Dafunc? Understanding functional programming with Haskell.
+ no side-effects, no mutability => maintainability
+ recursion
+ functions as first class “objects”: i.e. C++, 5; is a valid statement
+ lambdas
+ lists, maps, filters, folds
+ currying => just convenience
+ code example: Pythagoraian triangles, bubble sort
* Phuncy: The pythonic way is functional!
+ Not strictly functional
- recursion
+ fafco
- map, fold => example (sum of squares?)
+ python lambda syntax: lambda a,b: a+b
+ don't return lists, but iterators!
+ fold with reduce
+ Note: 2: map, filter, reduce, list comprehension
3: map, filter, functools.reduce(), list comprehension
+ The python2 to 3 page states:
“Removed `reduce()`. Use `functools.reduce()` if you really need it;
however, 99 percent of the time an explicit `for` loop is more
readable.”
+ Why use it? => Multi-processing, WTF Count.
```python
a = list(range(10))
b = 0
for i in a:
b += i**2
print(b)
```
vs.
```python
from functools import reduce
print(reduce(lambda x,y: x+y,map(lambda x: x**2,range(10))))
```
+ currying: not really, but binding via lambdas or functools.partial() or
https://mtomassoli.wordpress.com/2012/03/18/currying-in-python/
- decorators!
- still FP has advantages and is heavily used, i.e. in genomics (works on
tons of lengthy lists)
* FunCtional++: On the fast lane
- "Classical" C++ has some functional stuff, bust i.e. no lambdas (hardly usable)
- Changed with the new C++11-standard
- Buzzwords:
- `map` defines a Datatype in C++!
- lambdas in C++
```[](int x, int y) { return a`