6 ms·

Functional Eye for the Ruby Guy

26 points by rjsamson 14y ago

gkop 14y ago
Not sure what version of Ruby 2 the author is using here, but sadly the latest release candidate defines the using method only in the main scope; it's not available in a class definition, where he calls it in his example.
pjungwir 14y ago
I suppose this is a tangent, but a lot of this refactoring strikes me as obfuscation. Defining methods named `multiple_of_3` and `multiple_of_5` just to encapsulate a mod? I'd rather just read `x % 3 == 0` and `x % 5 == 0` than look up a method definition. And then he makes it worse by throwing those out, defining `multiple_of`, and using method_missing to make `multiple_of_{3,5}` still work. A big part of reading unfamiliar code is looking up the implementation of things, and this is just making it more laborious and confusing.
- martinced 14y ago
  "I'd rather just read x % 3..." Lots of people don't know of % works. Just as a lot of C / Java / C# programmers do not know the difference between "if a() & b()" and "if a() && b()". Note that I'm not saying it's great to use "if a() & b()". All I'm saying is most people do not know the difference. Try it if you interview people. It's fascinating. And, no, I'm not disqualifying people if they don't know the difference ; )
  - dllthomas 14y ago
    > Lots of people don't know of % works. God, really? But they know what a multiple is?
  - typicalrunt 14y ago
    Lots of people don't know of % works. Just as a lot of C / Java / C# programmers do not know the difference between "if a() & b()" and "if a() && b()" Funny you say that. And incredibly sad too. I have participated in interviewing many junior/mid/senior developers and you are correct that they trip up on the % operator. I've also experienced them tripping up on the word "modulo" and instead trying to calculate the remainder of a division operation by hand. While not trying to be elitist, I'm not sure what it says about our industry when a fundamental concept such as modulus is not understood by programmers.
    - dllthomas 14y ago
      That reminds me of a co-worker who was weirded out by my using "modulo" to mean "except for" or "ignoring" (which is, to my understanding, perfectly ordinary English). They did, thankfully, fully understand it in a mathematical context - to my knowledge I've never worked with someone who didn't, although this and nearby comments are leaving me wondering...
      - hackmiester 14y ago
        This is the first time I've heard it outside of a mathematical context. I'm an undergrad student.
        dllthomas 14y ago
        Not saying it's incredibly common, by any stretch. FWIW, wiktionary.com and thefreedictionary.com have the usage, Merriam Webster does not. Don't know about OED (don't have access).
      - pjungwir 14y ago
        I've occasionally tried to work out a sensible rationale for the non-mathematical meaning based on the mathematical one. Perhaps this is etymologically unsound, but hey, words are fun. But how do you get from "remainder when divided by" to "except"? I guess `x % y` gives you "the leftovers," which is close enough to "except."
        dllthomas 14y ago
        Oh, that's straightforward. In a truly mathematical context, modulo isn't really an operator per se. You can say, 10 = 7 modulo 3 Which is kinda, "10 = 7, except someone may have added some number of threes to each" - so, "10 = 7, but for the threes"
  - pjungwir 14y ago
    I doubt I'd hire a C programmer who didn't recognize a bit operator. Yikes! Even for Java/C#, it seems disconcerting, doesn't it?
- rustc 14y ago
  Completely agreed. Just defining a "multiple_of" method which takes n as a parameter would have better than the method_missing hack.
gfunk911 14y ago
This doesn't seem to be really utilizing the value of lazy enumerators. If this was correctly using lazy enumerators, it wouldn't require a range to be passed in, and you would take values from the resulting lazily evaluated enumerators until you found one >= 1000. All the laziness does here is prevent the select from being evaluated until the sum is called. I don't have 2.0 installed, so this probably has bugs/errors/etc, but I believe this is what he was going for. module TakeUntil refine Enumerator::Lazy do def take_until(&b) next_obj = take(1).first if yield(next_obj) [] else [next_obj] + take_until(&b) end end end end class FunctionalRuby using TakeUntil def sum_of_multiples_under(max) (1..99999999).lazy.select { |x| (x % 3 == 0) || (x % 5 == 0) }.take_until { |x| x > 1000 }.sum end end FunctionalRuby.new.sum_of_multiples_under(1000)
deleted 14y ago
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26 points by rjsamson 14y ago

gkop 14y ago

Not sure what version of Ruby 2 the author is using here, but sadly the latest release candidate defines the using method only in the main scope; it's not available in a class definition, where he calls it in his example.

pjungwir 14y ago

I suppose this is a tangent, but a lot of this refactoring strikes me as obfuscation. Defining methods named `multiple_of_3` and `multiple_of_5` just to encapsulate a mod? I'd rather just read `x % 3 == 0` and `x % 5 == 0` than look up a method definition. And then he makes it worse by throwing those out, defining `multiple_of`, and using method_missing to make `multiple_of_{3,5}` still work. A big part of reading unfamiliar code is looking up the implementation of things, and this is just making it more laborious and confusing.

martinced 14y ago
"I'd rather just read x % 3..." Lots of people don't know of % works. Just as a lot of C / Java / C# programmers do not know the difference between "if a() & b()" and "if a() && b()". Note that I'm not saying it's great to use "if a() & b()". All I'm saying is most people do not know the difference. Try it if you interview people. It's fascinating. And, no, I'm not disqualifying people if they don't know the difference ; )
- dllthomas 14y ago
  > Lots of people don't know of % works. God, really? But they know what a multiple is?
- typicalrunt 14y ago
  Lots of people don't know of % works. Just as a lot of C / Java / C# programmers do not know the difference between "if a() & b()" and "if a() && b()" Funny you say that. And incredibly sad too. I have participated in interviewing many junior/mid/senior developers and you are correct that they trip up on the % operator. I've also experienced them tripping up on the word "modulo" and instead trying to calculate the remainder of a division operation by hand. While not trying to be elitist, I'm not sure what it says about our industry when a fundamental concept such as modulus is not understood by programmers.
  - dllthomas 14y ago
    That reminds me of a co-worker who was weirded out by my using "modulo" to mean "except for" or "ignoring" (which is, to my understanding, perfectly ordinary English). They did, thankfully, fully understand it in a mathematical context - to my knowledge I've never worked with someone who didn't, although this and nearby comments are leaving me wondering...
    - hackmiester 14y ago
      This is the first time I've heard it outside of a mathematical context. I'm an undergrad student.
      - dllthomas 14y ago
        Not saying it's incredibly common, by any stretch. FWIW, wiktionary.com and thefreedictionary.com have the usage, Merriam Webster does not. Don't know about OED (don't have access).
    - pjungwir 14y ago
      I've occasionally tried to work out a sensible rationale for the non-mathematical meaning based on the mathematical one. Perhaps this is etymologically unsound, but hey, words are fun. But how do you get from "remainder when divided by" to "except"? I guess `x % y` gives you "the leftovers," which is close enough to "except."
      - dllthomas 14y ago
        Oh, that's straightforward. In a truly mathematical context, modulo isn't really an operator per se. You can say, 10 = 7 modulo 3 Which is kinda, "10 = 7, except someone may have added some number of threes to each" - so, "10 = 7, but for the threes"
- pjungwir 14y ago
  I doubt I'd hire a C programmer who didn't recognize a bit operator. Yikes! Even for Java/C#, it seems disconcerting, doesn't it?
rustc 14y ago
Completely agreed. Just defining a "multiple_of" method which takes n as a parameter would have better than the method_missing hack.

gfunk911 14y ago

This doesn't seem to be really utilizing the value of lazy enumerators. If this was correctly using lazy enumerators, it wouldn't require a range to be passed in, and you would take values from the resulting lazily evaluated enumerators until you found one >= 1000. All the laziness does here is prevent the select from being evaluated until the sum is called. I don't have 2.0 installed, so this probably has bugs/errors/etc, but I believe this is what he was going for. module TakeUntil refine Enumerator::Lazy do def take_until(&b) next_obj = take(1).first if yield(next_obj) [] else [next_obj] + take_until(&b) end end end end class FunctionalRuby using TakeUntil def sum_of_multiples_under(max) (1..99999999).lazy.select { |x| (x % 3 == 0) || (x % 5 == 0) }.take_until { |x| x > 1000 }.sum end end FunctionalRuby.new.sum_of_multiples_under(1000)

deleted 14y ago

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