How do I modify a variable in Haskell?

Re:How do I modify a variable in Haskell? by brudgers on Tuesday August 15, 2017 @11:02AM (#15018835)

{caveat: I am pretty sure that there are other ways to write the Haskell code at a higher level. I wrote this not as a rant about Haskell, but because I have been thinking about 'big versus small' languages, recently.}

For me, I want a big language, not more correct assembly or C. An identity matrix in Racket is three lines:

  #lang racket
  (require math/matrix)
  (identity-matrix 10)

Or more iteratively:

  #lang racket
  (require math/matrix)
  (diagonal-matrix 
    (build-list 10 (lambda (x) (values 1))))

Or more generically:

  #lang racket
  (require math/matrix)
  (build-matrix 10 10
    (lambda (x y)
      (if (= x y)
        (values 1)
        (values 0))))

The choice three different abstractions in fewer lines of code than the single Haskell abstraction. For all its type safety the Haskell abstraction is down and dirty Von Neumann style sequential memory access. Looping over the elements of a matrix is pretty far away from the useful abstractions of matrices.

To put it another way, i's and j's are good variable names for loops and bad variable names for matrices...If I have to iterate over elements of a matrix, I really want m's and n's. But that conflicts with semantics of a conventional looping construct.

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Re:How do I modify a variable in Haskell? by tome on Tuesday August 15, 2017 @11:13AM (#15018963)

> caveat: I am pretty sure that there are other ways to write the Haskell code at a higher level. I wrote this not as a rant about Haskell, but because I have been thinking about 'big versus small' languages, recently

> The choice three different abstractions in fewer lines of code than the single Haskell abstraction

These two parts of your comment don't seem to mesh :)

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Re:How do I modify a variable in Haskell? by brudgers on Tuesday August 15, 2017 @01:37PM (#15020419)

In 'big languages' I am thinking more about how much 'talking about' domain specific topics looks like 'talking about' the topics covered in the core language. Or maybe about how easy it is to make 'talking about' domain topics look like 'talking about' core topics. Maybe it's the degree to which the reductionist process of dividing up code into files is typically reflected when writing code.

Some languages like Python default to explicitly referencing the module, that is the happy easy path leads to writing "math.floor(x)," not "floor(x)." That's even after I write the mandatory "import math." C is probably close to one end of the spectrum, and at the other end of the spectrum are languages like Wolfram, where:

  GeoDistance
   [Entity["City", {"NewYork", "NewYork", "UnitedStates"}], 
    Entity["City", {"LosAngeles", "California", "UnitedStates"}]]

Racket is probably closer to Wolfram, and Haskell closer to C. I think the C end is more likely the more a language tries to solve problems that programs don't have before they are written...e.g. speed and type errors. The Wolfram end tries to solve problems that programmers have before programs are written...e.g. what do I want to say.

Wishful thinking is often Abelson's starting point in the SICP lectures. That's a bit at odds with the philosophy of some languages.

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Re:How do I modify a variable in Haskell? by yawaramin on Wednesday August 16, 2017 @10:08AM (#15027549)

https://news.ycombinator.com/item?id=15022244

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