This document discusses the Operator::Util module in Perl, which provides meta-operators for reduction, zipping, crossing, and hyper operations on lists and hashes. It shows examples of using reduce, zip, cross, and hyper to perform common math, string, and list operations. It also demonstrates how to chain operations, handle different arities, and control associativity. The module provides shortcuts for common uses as well as options to control behavior.

1. Operator::Util
Nick Patch
Perl Seminar NY
15 February 2011

2. released yesterday

3. released yesterday
i ♥ feedback

4. Perl 6 is pretty cool

5. meta-operators

6. meta-operators
[ ☺] Z ☺ X ☺ » ☺«

7. reduction
[+] 1..4 # 10
[*] 1..4 # 24
[~] 'a'..'d' # 'abcd'

8. zip
(1,2) Z+ (2,3) # 3,5
(1,2) Z* (2,3) # 2,6
(1,2) Z~ <a b> # 1a,2b

9. cross (flat)
(1,2) X+ (2,3) # 3,4,4,5
(1,2) X* (2,3) # 2,3,4,6
(1,2) X~ <a b> # 1a,1b,2a,2b

10. cross (lol)
(1,2) X+ (2,3) # [3,4],[4,5]
(1,2) X* (2,3) # [2,3],[4,6]
(1,2) X~ <a b> # [1a,1b],[2a,2b]

11. hyper
1..4 »~« 'a'..'d' # 1a,2b,3c,4d
1..4 »~» 'x' # 1x,2x,3x,4x
1..4 «~» <x y> # 1x,2y,1x,2y
1..4 «~« <x y> # 1x,2y

12. more hyper!
-« (1,2,3) # -1,-2,-3
[1,[2,3]] »++ # [2,[3,4]]
%foo «+» %bar # intersection
%foo »+« %bar # union
%foo »+=« %bar # %foo = union

13. but it's not Xmas yet

14. cpanm Operator::Util

15. use Operator::Util qw(
reducewith
zipwith
crosswith
hyperwith
);

16. reducewith a.k.a. reduce
hyperwith a.k.a. hyper

17. reduction
reduce('+', [1..4]) # 10
reduce('*', [1..4]) # 24
reduce('.', ['a'..'d']) # 'abcd'

18. zip
zipwith('+', [1,2], [2,3]) # 3,5
zipwith('*', [1,2], [2,3]) # 2,6
zipwith('.', [1,2], ['a','b']) # 1a,2b

19. cross (flat)
crosswith('+', [1,2], [2,3])
crosswith('*', [1,2], [2,3])
crosswith('.', [1,2], ['a','b'])
# 3,4,4,5
# 2,3,4,6
# 1a,1b,2a,2b

20. cross (lol)
crosswith('+', [1,2], [2,3], flat=>0)
crosswith('*', [1,2], [2,3], flat=>0)
crosswith('.', [1,2], ['a','b'], flat=>0)
# [3,4],[4,5]
# [2,3],[4,6]
# [1a,1b],[2a,2b]

21. hyper
hyper('.', [1..4], ['a'..'d'] );
hyper('.', [1..4], 'x', dwim_right=>1);
hyper('.', [1..4], ['x','y'], dwim=>1 );
hyper('.', [1..4], ['x','y'], dwim_left=>1 );
# 1a,2b,3c,4d
# 1x,2x,3x,4x
# 1x,2y,1x,2y
# 1x,2y

22. more hyper!
hyper('prefix:-', [1,2,3]);
hyper('postfix:++', [1,[2,3]]);
hyper('+', %foo, %bar, dwim=>1);
hyper('+', %foo, %bar);
hyper('+=', %foo, %bar);
# -1,-2,-3
# [2,[3,4]]
# intersection
# union
# %foo = union

23. default ops
zipwith(',', [1,2], ['a','b'])
zip( [1,2], ['a','b'])
crosswith(',', [1,2], ['a','b'])
cross( [1,2], ['a','b'])
# 1,a,2,b
# 1,a,2,b
# 1,a,1,b,2,a,2,b
# 1,a,1,b,2,a,2,b

24. associativity
reduce('-', [4, 3, 2])
reduce('**', [4, 3, 2])
# 4-3-2 = (4-3)-2 = -1
# 4**3**2 = 4**(3**2) = 262144

25. chaining
reduce('eq', @a) # all elements eq?
reduce('!=', @c) # no repeating elements?
reduce('<', @b) # ascending elements?

26. dwim for < 2 elems
reduce('+', [] ) # 0
reduce('+', [5]) # 5
reduce('*', [] ) # 1
reduce('*', [5]) # 5

27. even more hyper!
hyper('->', @objects, 'run', dwim=>1)
hyper('+', [[1, 2], 3], [4, [5, 6]], dwim=>1)
hyper('prefix:-', {a => 1, b => 2, c => 3})
# call ->run() on each
# [[5, 6], [8, 9]]
# a => -1, b => -2, c => -3

28. resources
git: github.com/patch
slides: patch.github.com