↳ In-reply-to » It is such a nice feeling that Mu is such a capable little language 😅 And I decided to write code code in Mu by hand 🤚 haha 🤣 and start solving Project Euler problems, like Problem 8 which works out to be a nice elegant solution in Mu:

Oh man wow 😮 Problem 9 was quite hard 😱 I had to build two new functions in the Mu stdlib for computing combinations and permutations, but then the combinations of range(1000) for triples such as a + b == c is enormous! So i had to write iterator versions of these to do lazy evaluation. Anyway solution follows:

#!/usr/bin/env mu

// Special Pythagorean Triplet

import "iter"

fn usage() {
  print("Usage:", args()[0], "<n>")
}

fn sqr(x) { x * x }

fn main() {
  if len(args()) < 2 {
    usage()
    exit(1)
  }

  n := must(int(args()[1]))
  print("n:", n)

  // For a < b < c and a + b + c == n, both a and b are strictly less
  // than n/2. Generate only (a,b) combinations and derive c directly. This
  // keeps the search lazy and reduces n=1000 from C(999,3) = 165,668,499
  // candidate triples to C(499,2) = 124,251 candidate pairs.
  pairs := iter.combinations(iter.range(1, n / 2), 2)

  triples := iter.map(pairs, fn(xs) {
    a := xs[0]
    b := xs[1]
    return [a, b, n - a - b]
  })

  // Enforce b < c; a < b is already guaranteed by combinations over an
  // increasing range, and a + b + c == n holds by construction.
  triples = iter.filter(triples, fn(xs) {
    return xs[1] < xs[2]
  })

  // Euler 9 has one answer for n=1000. find() stops the entire upstream
  // iterator chain as soon as the first Pythagorean triple is found.
  answer := iter.find(triples, fn(xs) {
    return sqr(xs[0]) + sqr(xs[1]) == sqr(xs[2])
  })

  print(answer)

  if answer != nil {
    print(answer[0] * answer[1] * answer[2])
  }
}

main()