(i just wrote (non-elegant) Python code.)

Could you share a short, VERY Readable Pythonic (or Lisp, Scheme) code
that solves this?

Thank you!

https://i.imgur.com/72LGJjj.jpeg

3 digit lock
[682]: One number is correct and well-placed
[614]: One number is correct but wrongly placed
[206]: Two numbers are correct but wrongly placed
[738]: Nothing is correct
[780]: One number is correct but wrongly placed

HINT -- A mark of a great puzzle, this one contains a surprise or two.

On Sun, 25 Feb 2024 20:27:42 -0800, HenHanna wrote:

> Could you share a short, VERY Readable Pythonic (or Lisp, Scheme) code
> that solves this?

This is my answer after spending this afternoon learning Guile. Much
more wordy than the Python version I previously posted. Anybody know
how to do it better?

(import
(rnrs base)
(rnrs lists)
)

(define (range n)
; returns a list of integers from 0 up to n - 1 inclusive.
(letrec
(
(subrange
(lambda (n)
(cond
((>= n 0) (cons n (subrange (- n 1))))
(#t '())
) ; cond
) ; lambda
)
)
(reverse (subrange (- n 1)))
) ; let
) ; define

(define (score candidate answer)
(let
(
(in-right-place 0)
(in-wrong-place 0)
)
(for-each
(lambda (a)
(for-each
(lambda (b)
(when (eq? a b)
(set! in-wrong-place (+ in-wrong-place 1))
; might be in right place, fixed up below
) ; when
) ; lambda
answer
) ; for-each
) ; lambda
candidate
) ; for-each
(for-each
(lambda (a b)
(when (eq? a b)
(set! in-right-place (+ in-right-place 1))
(set! in-wrong-place (- in-wrong-place 1))
) ; when
) ; lambda
candidate
answer
) ; for-each
(list in-right-place in-wrong-place)
) ; let
) ; score

(define required-scores
'(
((6 8 2) (1 0))
((6 1 4) (0 1))
((2 0 6) (0 2))
((7 3 8) (0 0))
((7 8 0) (0 1))
)
)

(for-each
(lambda (n)
(let-values
(
((a b c answer) (values #f #f #f #f))
)
(set! a (div n 100))
(set! n (- n (* a 100)))
(set! b (div n 10))
(set! c (- n (* b 10)))
(set! answer (list a b c))
(when
(for-all
(lambda (candidate)
(let
(
(required-score (cadr candidate))
)
(set! candidate (car candidate))
(equal? (score candidate answer) required-score)
) ; let
) ; lambda
required-scores
) ; for-all
(display answer)
(display "\n")
) ; when
) ; let-values
) ; lambda
(range 1000)
) ; let

Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> This is my answer after spending this afternoon learning Guile. Much
> more wordy than the Python version I previously posted. Anybody know
> how to do it better?

The following works for me as a fairly simple port of the concise Python
version to Guile. Note that the parenthesis style is pretty much
universal in Lisp and variants. Editors support it, and automatic paren
balancing in the editors keep them from getting too confusing.

If you want to understand Scheme, I suggest reading through SICP (click
the open access link at mitpress.mit.edu/sicp for a download). That
said, I'm not much of a Scheme user myself, so the below might have some
style issues.

I think by now, the methods introduced in Scheme have moved on to newer
languages like OCaml and then Haskell, so you might want to study those
instead. learnyouahaskell.com is a good start with Haskell.

================================================================

(use-modules (srfi srfi-1)
(srfi srfi-11))

(define clues '((682 1 0) (614 0 1) (206 0 2) (738 0 0) (780 0 1)))
(define (digits n)
(values (quotient n 100) (remainder (quotient n 10) 10) (remainder n 10)))
(define (count . args) (length (filter identity args)))

(define (score candidate answer)
(let-values (((a b c) (digits candidate))
((x y z) (digits answer)))
(let ((well-placed (count (= a x) (= b y) (= c z)))
(wrongly-placed (count (or (= a y) (= a z))
(or (= b x) (= b z))
(or (= c x) (= c y)))))
(values well-placed wrongly-placed))))

(define (test)
(let ((n 682) (a 1) (b 0))
(let-values (((well-placed wrongly-placed) (score n 042)))
(and (= a well-placed) (= b wrongly-placed)))))

(define (check candidate)
(define (check1 clue)
(let ((n (car clue))
(a (cadr clue))
(b (caddr clue)))
(let-values (((well-placed wrongly-placed) (score candidate n)))
(and (= a well-placed) (= b wrongly-placed)))))
(every check1 clues))

(display (filter check (iota 1000)))
(newline)

On Tue, 27 Feb 2024 11:22:08 -0800, Paul Rubin wrote:

> Note that the parenthesis style is pretty much universal in Lisp and
> variants.

Sorry, not a fan of “parenthesis pileup” layout.

On 2024-02-27, Paul Rubin <no.email@nospam.invalid> wrote:
> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>> This is my answer after spending this afternoon learning Guile. Much
>> more wordy than the Python version I previously posted. Anybody know
>> how to do it better?
>
> The following works for me as a fairly simple port of the concise Python
> version to Guile.

Based on code formatting alone, I'm declaring yours vastly better.

The problem is actually trivial.

All you have to do is close your parentheses ))) like a sane person, and
the solution will pop out sooner or later.

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca

On 2024-02-27, Lawrence D'Oliveiro <ldo@nz.invalid> wrote:
> On Tue, 27 Feb 2024 11:22:08 -0800, Paul Rubin wrote:
>
>> Note that the parenthesis style is pretty much universal in Lisp and
>> variants.
>
> Sorry, not a fan of “parenthesis pileup” layout.

You've certainly come to the right language family, if you want to
forever hack by yourself, doing things Your Way.

I suspect you're doing your formatting manually, though, which takes
more effort. The parentheses pileup is well supported in editors.

If you don't want collaborators, you can just communicate that
explicitly (e.g. a block comment saying ";; this is my solo work,
patches will be rejected regardless of quality") and not inflict an
unergonomic way of working on yourself.

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca

Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> This is my answer after spending this afternoon learning Guile. Much
> more wordy than the Python version I previously posted. Anybody know
> how to do it better?

The "parenthesis pileup" aside, the following things jump out at me:

1) Your "range" function already exists, called "iota" (after the iota
operation in APL).

2) Even if it didn't exist, your recursive definition is messy.
This is more idiomatic:

(define (range n)
(define (go n a)
(if (< n 0)
a
(go (1- n) (cons n a))))
(go n 0))

Note that the accumulation parameter in "go" makes go tail recursive, so
it uses a fixed number of stack cells.

2) Similarly the "score" function looks translated from C to Scheme or
something like that. Generally, the use of set! is a code smell in
Scheme. It's preferable to use recursion and combinators like map and
filter. In Haskell, set! doesn't even exist in any convenient form.

Without destructive updates, you end up using a programming style with a
rather different set of idioms. Scheme was an early enabler of that
style. Lisp predated Scheme and was sort of an intermediate step.
See the SICP book for a deeper intro.

Paul Rubin <no.email@nospam.invalid> writes:
> (define (range n) ...

Oops:

(define (range n)
(define (go n a)
(if (< n 0)
a
(go (1- n) (cons n a))))
(go (1- n) '()))

On Tue, 27 Feb 2024 13:36:25 -0800, Paul Rubin wrote:

> 1) Your "range" function already exists, called "iota" (after the iota
> operation in APL).

Just checked, and I don’t even need to import anything to use it. Thanks.

> 2) Similarly the "score" function looks translated from C to Scheme or
> something like that.

It was my attempt to translate this Python code:

def score(candidate, answer) :
return \
(
sum(a == b for a, b in zip(candidate, answer)),
sum
(
i != j and a == b
for i, a in enumerate(candidate)
for j, b in enumerate(answer)
)
)
#end score

Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> sum(a == b for a, b in zip(candidate, answer))

zip is in srfi-1 but I would write this as

(length (filter identity (map = candidate answer)))

> sum
> (
> i != j and a == b
> for i, a in enumerate(candidate)
> for j, b in enumerate(answer)
> )
> )

In Python you might avoid the nested loops by writing that in terms of
set or multiset (collections.Counter) intersections. In Scheme, maybe
this:

(define (score2 candidate answer)
(let* ((well-placed (length (filter identity (map = candidate answer))))
(wrongly-placed (- (length (lset-intersection = candidate answer))
well-placed)))
(values well-placed wrongly-placed)))

lset-intersection is also in srfi-1. Here, candidate and answer are
both lists of digits. I don't know the running time (complexity) of
lset-intersection. In Python, sets are represented with hashes so the
equivalent operation should take linear time. Scheme might uses hashes
(linear time), sorted lists (n log n time), or quadratic time.

On Tue, 27 Feb 2024 17:46:48 -0800, Paul Rubin wrote:

> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>
>> sum
>> (
>> i != j and a == b for i, a in enumerate(candidate)
>> for j, b in enumerate(answer)
>> )
>
> In Python you might avoid the nested loops by writing that in terms of
> set or multiset (collections.Counter) intersections.

Why would that be better?

On Wed, 28 Feb 2024 21:57:46 -0000 (UTC), Lawrence D'Oliveiro
<ldo@nz.invalid> wrote:

>On Tue, 27 Feb 2024 17:46:48 -0800, Paul Rubin wrote:
>
>> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>>
>>> sum
>>> (
>>> i != j and a == b for i, a in enumerate(candidate)
>>> for j, b in enumerate(answer)
>>> )
>>
>> In Python you might avoid the nested loops by writing that in terms of
>> set or multiset (collections.Counter) intersections.
>
>Why would that be better?

Because almost all of Python's standard libraries are written in C.
Most versions of Python are just too slow to use for anything but toy
programs.

Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>> In Python you might avoid the nested loops by writing that in terms of
>> set or multiset (collections.Counter) intersections.
> Why would that be better?

You are trying to handle N digits and your algorithm does O(N**2)
comparisons. Ok, I guess the whole search strategy is impractical if N
is larger than just a few, and in traditional Mastermind N=4, so maybe
that isn't an issue. But the idea is that sets in Python are
implemented with hashing, so finding a set intersection is takes O(N).

A purely functional approach (idk how lset in Guile works) might use
sorted lists for O(N log N) complexity, but either beats O(N**2).

On Wed, 28 Feb 2024 15:54:48 -0800, Paul Rubin wrote:

> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>>
>> Why would that be better?
>
> You are trying to handle N digits and your algorithm does O(N**2)
> comparisons. Ok, I guess the whole search strategy is impractical if N
> is larger than just a few, and in traditional Mastermind N=4, so maybe
> that isn't an issue.

“Premature optimization is the root of all evil.”
-- variously attributed to Tony Hoare or Donald Knuth

Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> “Premature optimization is the root of all evil.”

I would say using set intersections is clearer and more concise than
that code with loop indices too. It is what you were trying to compute
in the first place. Same idea as writing a matrix product as A*B
instead of as some messy thing with subscripts.

On Thu, 29 Feb 2024 14:21:12 -0800, Paul Rubin wrote:

> Same idea as writing a matrix product as A*B instead of as some messy
> thing with subscripts.

Somebody still has to write the underlying code with the subscripts.

On 2024-02-29, Lawrence D'Oliveiro <ldo@nz.invalid> wrote:
> On Wed, 28 Feb 2024 15:54:48 -0800, Paul Rubin wrote:
>
>> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>>>
>>> Why would that be better?
>>
>> You are trying to handle N digits and your algorithm does O(N**2)
>> comparisons. Ok, I guess the whole search strategy is impractical if N
>> is larger than just a few, and in traditional Mastermind N=4, so maybe
>> that isn't an issue.
>
> “Premature optimization is the root of all evil.”
> -- variously attributed to Tony Hoare or Donald Knuth

Pinning it down more precisely at this stage would be premature
attribution.

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca

Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> Somebody still has to write the underlying code with the subscripts.

Sure, that's pushed down into a library or helper function though.
Doing it at the higher level is related to the "primitive obsession"
antipattern. It's normal to bang out code like that when you're trying
to keep moving, but refactoring afterwards generally helps. Here's a
refactored Python version of the score function I posted earlier:

def score(answer: int, candidate: int) -> Tuple[int,int]:
a = digits(answer)
b = digits(candidate)
well_placed = sum(x==y for x,y in zip(a,b))
wrongly_placed = len(set(a) & set(b)) - well_placed
return well_placed, wrongly_placed

Maybe it's more correct to use multisets (collections.Counter) instead
of sets, depending on how the problem is specified.

On Thu, 29 Feb 2024 18:18:31 -0800, Paul Rubin wrote:

> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>
>> Somebody still has to write the underlying code with the subscripts.
>
> Sure, that's pushed down into a library or helper function though. Doing
> it at the higher level is related to the "primitive obsession"
> antipattern.

I only push things into separate/library functions if I’m going to reuse
them. Splitting things off just for the sake of doing so is what we could
call a “fragmentation smell” or a “gratuitous hierarchy antipattern”.

Lawrence D'Oliveiro <ldo@nz.invalid> writes:
> I only push things into separate/library functions if I’m going to reuse
> them. Splitting things off just for the sake of doing so is what we could
> call a “fragmentation smell” or a “gratuitous hierarchy antipattern”.

In the case of matrix multiplication, the code is already in a linear
algebra library. In the case of set intersection, it is built into
Python's set type.

On Di 27 Feb 2024 at 13:36, Paul Rubin <no.email@nospam.invalid> wrote:

> The "parenthesis pileup" aside, the following things jump out at me:
>
> 1) Your "range" function already exists, called "iota" (after the iota
> operation in APL).
>
> 2) Even if it didn't exist, your recursive definition is messy.
> This is more idiomatic:
>
> (define (range n)
> (define (go n a)
> (if (< n 0)
> a
> (go (1- n) (cons n a))))
> (go n 0))
>
I would write it without the second define using a named let:

(define (range n)
(let go ((n n) (a '()))
(if (< n 0)
a
(go (1- n) (cons n a)))))

'Andreas

--
ceterum censeo redmondinem esse delendam

Andreas Eder <a_eder_muc@web.de> writes:
> I would write it without the second define using a named let:
>
> (define (range n)
> (let go ((n n) (a '())) ...

Oh interesting, I didn't know that syntax. I will check the docs. Thanks.

On Fri, 01 Mar 2024 11:50:36 +0100, Andreas Eder wrote:

> (define (range n)
> (let go ((n n) (a '()))
> (if (< n 0)
> a
> (go (1- n) (cons n a)))))

Interesting. r6rs (section 11.4.6) doesn’t seem to allow that form. Also
it would seem you would need “letrec” rather than “let”, but that doesn’t
work for me.

On Fri, 1 Mar 2024 21:08:13 -0000 (UTC), Lawrence D'Oliveiro
<ldo@nz.invalid> wrote:

>On Fri, 01 Mar 2024 11:50:36 +0100, Andreas Eder wrote:
>
>> (define (range n)
>> (let go ((n n) (a '()))
>> (if (< n 0)
>> a
>> (go (1- n) (cons n a)))))
>
>Interesting. r6rs (section 11.4.6) doesn’t seem to allow that form. Also
>it would seem you would need “letrec” rather than “let”, but that doesn’t
>work for me.

Named Let is not a binding construct - it's a looping construct.
See 11.16

George Neuner <gneuner2@comcast.net> writes:
> Named Let is not a binding construct - it's a looping construct.
> See 11.16

Thanks, I wonder if that is something relatively recent (i.e. arrived
between r4rs and r6rs). It is kind of ugly and I'm used to seeing
nested defines. Maybe there are some situations where the named let is
more convenient. Or maybe I can get used to it.

Part of the idea of Guile was to be the execution engine for various
other languages that would get transpiled to Scheme, but idk if that
went anywhere.