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You should not approach problems in functional languages with imperative techniques. It's fitting a square peg in a round hole. The approaches & data structur

You should not approach problems in functional languages with imperative techniques. It's fitting a square peg in a round hole. The approaches & data structures aren't always the same. In my experience with FP you start with more of a top down approach in contrast to the bottom up approach discussed in the blog post. There are many good resources on this. I've referenced a few below. Of course there are many more. [1] https://www.amazon.com/Pearls-Functional-Algorithm-Design-Richard/dp/0521513383 https://www.amazon.com/Pearls-Functional-Algorithm-Design-Ri... [2] https://www.amazon.com/Purely-Functional-Data-Structures-Okasaki/dp/0521663504 https://www.amazon.com/Purely-Functional-Data-Structures-Oka... [3] https://www.amazon.com/Algorithm-Design-Haskell-Richard-Bird/dp/1108491618 https://www.amazon.com/Algorithm-Design-Haskell-Richard-Bird... [4] https://www.amazon.com/Structure-Interpretation-Computer-Programs-Engineering/dp/0262510871 https://www.amazon.com/Structure-Interpretation-Computer-Pro...

exdsq 5y ago
Thanks for these links, commenting to find them later.
- Jtsummers 5y ago
  If you select the timestamp of a comment (also when you reply to it) you can favorite it. This is much cleaner than leaving scattered "to find them later" comments around this site (in fact, I'm pretty sure it was added precisely to avoid those kinds of comments). You can also favorite submissions themselves. Favorites can be found in your profile.
  - exdsq 5y ago
    Cool, didn’t know that! Cheers
  - bckr 5y ago
    you can click the timestamp and just keep the URL somewhere, like your browser's bookmarks
dehrmann 5y ago
> You should not approach problems in functional languages with imperative techniques. It's fitting a square peg in a round hole. This might be part of the problem with FP. Every popular CPU architecture is imperative.
- nightski 5y ago
  I was more talking about how you approach solving problems, not the execution model. You can still get tight imperative loops in FP, it's just approached differently than in a traditionally imperative language. Everything is a tradeoff. FP gives you a lot of flexibility in how you trade space and time of the execution of your program. It's also not a magic wand, just a really powerful tool.
- TuringTest 5y ago
  > Every popular CPU architecture is imperative. That's arguable, given that every (deterministic) imperative computation can be expressed as a pure functional program. "Imperative" is more of a viewpoint that the developer is using to understand the behavior of the computer, rather than a property of the machine itself. A pure functional analysis will describe a computation on that "imperative" architecture as an inmutable, monotonic sequence of all the states that the CPU goes through over time; or maybe, if you know enough PL theory, as a chain of rewritings of a program-long expression that is updated, one term at a time, when each expression is replaced by the result of a function as it consumes its input parameters. And no viewpoint is inherently better than the other (except that the functional version can be analyzed in a natural way with mathematical tools, which is often difficult with the imperative description).
  - whimsicalism 5y ago
    Not really arguable, IMO. Just because both lambda calculus and assembly are Turing complete does not mean that CPU architecture isn't clearly imperative.
    - TuringTest 5y ago
      How do you define "imperative" in a way that precludes a functional description of your definition? I'd say that if you're able to do that, you'd have found a contradiction in Turing completeness and win you a Turing award. Also, this: https://news.ycombinator.com/item?id=30883863 https://news.ycombinator.com/item?id=30883863
rramadass 5y ago
I think anybody who wants to understand Functional Programming should start with Lambda Calculus. I highly recommend An Introduction to Functional Programming Through Lambda Calculus by Greg Michaelson. You can then see how to express Functional Techniques in your language of choice (i.e. one you already know well eg; Functional Programming in C++ by Ivan Cukic) before learning a new Functional Language. This is to avoid the confusion in syntax/semantic expression of unfamiliar concepts which is a bit too much for a beginning student to handle simultaneously.

exdsq 5y ago

Thanks for these links, commenting to find them later.

Jtsummers 5y ago
If you select the timestamp of a comment (also when you reply to it) you can favorite it. This is much cleaner than leaving scattered "to find them later" comments around this site (in fact, I'm pretty sure it was added precisely to avoid those kinds of comments). You can also favorite submissions themselves. Favorites can be found in your profile.
- exdsq 5y ago
  Cool, didn’t know that! Cheers
- bckr 5y ago
  you can click the timestamp and just keep the URL somewhere, like your browser's bookmarks

dehrmann 5y ago

> You should not approach problems in functional languages with imperative techniques. It's fitting a square peg in a round hole. This might be part of the problem with FP. Every popular CPU architecture is imperative.

nightski 5y ago
I was more talking about how you approach solving problems, not the execution model. You can still get tight imperative loops in FP, it's just approached differently than in a traditionally imperative language. Everything is a tradeoff. FP gives you a lot of flexibility in how you trade space and time of the execution of your program. It's also not a magic wand, just a really powerful tool.
TuringTest 5y ago
> Every popular CPU architecture is imperative. That's arguable, given that every (deterministic) imperative computation can be expressed as a pure functional program. "Imperative" is more of a viewpoint that the developer is using to understand the behavior of the computer, rather than a property of the machine itself. A pure functional analysis will describe a computation on that "imperative" architecture as an inmutable, monotonic sequence of all the states that the CPU goes through over time; or maybe, if you know enough PL theory, as a chain of rewritings of a program-long expression that is updated, one term at a time, when each expression is replaced by the result of a function as it consumes its input parameters. And no viewpoint is inherently better than the other (except that the functional version can be analyzed in a natural way with mathematical tools, which is often difficult with the imperative description).
- whimsicalism 5y ago
  Not really arguable, IMO. Just because both lambda calculus and assembly are Turing complete does not mean that CPU architecture isn't clearly imperative.
  - TuringTest 5y ago
    How do you define "imperative" in a way that precludes a functional description of your definition? I'd say that if you're able to do that, you'd have found a contradiction in Turing completeness and win you a Turing award. Also, this: https://news.ycombinator.com/item?id=30883863 https://news.ycombinator.com/item?id=30883863

rramadass 5y ago

I think anybody who wants to understand Functional Programming should start with Lambda Calculus. I highly recommend An Introduction to Functional Programming Through Lambda Calculus by Greg Michaelson. You can then see how to express Functional Techniques in your language of choice (i.e. one you already know well eg; Functional Programming in C++ by Ivan Cukic) before learning a new Functional Language. This is to avoid the confusion in syntax/semantic expression of unfamiliar concepts which is a bit too much for a beginning student to handle simultaneously.