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-rw-r--r--README.md34
-rw-r--r--aoc/2021/day01/input.txt2000
-rw-r--r--aoc/2021/day01/part1.neb55
-rw-r--r--aoc/2021/day01/part2.neb19
-rw-r--r--aoc/2021/day02/input.txt6
-rw-r--r--aoc/2021/day02/part1.neb44
-rw-r--r--aoc/2021/day03/input.txt12
-rw-r--r--aoc/2021/day03/part1.neb73
-rw-r--r--aoc/2021/day04/input.txt19
-rw-r--r--aoc/2021/day04/part01.neb101
-rw-r--r--p99/p01.neb5
-rw-r--r--p99/p02.neb8
-rw-r--r--p99/p03.neb10
-rw-r--r--p99/p04.neb5
-rw-r--r--p99/p05.neb5
-rw-r--r--p99/p06.neb23
-rw-r--r--p99/p07.neb57
-rw-r--r--p99/p08.neb57
-rw-r--r--p99/p09.neb31
-rw-r--r--p99/p10.neb15
-rw-r--r--p99/p11.neb25
-rw-r--r--p99/p12.neb37
-rw-r--r--p99/p13.neb30
-rw-r--r--p99/p14.neb15
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-rw-r--r--p99/p16.neb19
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-rw-r--r--p99/p18.neb27
-rw-r--r--p99/p19.neb15
-rw-r--r--p99/p20.neb21
-rw-r--r--p99/p21.neb16
-rw-r--r--rosetta/factors-of-int.neb41
-rw-r--r--rosetta/lev.neb20
-rw-r--r--rosetta/lines.neb16
-rw-r--r--rosetta/luhn.neb73
-rw-r--r--rosetta/palindrome.neb6
-rw-r--r--rosetta/sum-of-squares.neb2
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diff --git a/README.md b/README.md
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+# neb examples
+
+Some examples of neb code, using well known and/or widely available problems.
+
+**All examples should be runnable with the latest neb-python interpreter.**
+As the compiler (neb-d) matures, it should be able to run more and more of
+these examples.
+
+The purpose of this repo is two-fold:
+1. Provide working examples to anyone (including my future self) who is
+interested in writing *scare-quotes* ideomatic neb.
+2. By working through examples, locate the rough edges of the language
+(where do things not work/look-or-feel wrong), and use that to *refine* the
+language (both the core syntax and available functions in a standard lib).
+
+## is this really ideomatic neb?
+
+I mean, I don't have a PEP20/PEP8-esque reference document, but this is probably
+as close as things get to ideomatic at this point. Also, as the language
+changes for whatever reason(s), so too will some of the styles (both to
+accomodate breaking changes, and to take advantage of new formats). I also
+try to make comments around bits of code I find particularly clunky, so those
+areas are probably the most likely to change.
+
+## dude, your code is bad...
+
+I'm sure you're right! I'd love to hear any specific feedback on either the
+language or the code written in it. I am not the World's Best Coder by any
+stretch, and so am very open to learning new things and rectifying my mistakes!
+
+## key to examples
+ - `aoc`: [Advent of Code](https://adventofcode.com)
+ - `p99`: [Ninety-Nine Lisp Problems](https://www.ic.unicamp.br/~meidanis/courses/mc336/problemas-lisp/L-99_Ninety-Nine_Lisp_Problems.html)
+ - `rosetta`: [Rosetta Code](https://rosettacode.org/wiki/Rosetta_Code) (Note: the names of the problems don't line up well)
diff --git a/aoc/2021/day01/input.txt b/aoc/2021/day01/input.txt
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diff --git a/aoc/2021/day01/part1.neb b/aoc/2021/day01/part1.neb
new file mode 100644
index 0000000..066a86d
--- /dev/null
+++ b/aoc/2021/day01/part1.neb
@@ -0,0 +1,55 @@
+;; https://adventofcode.com/2021/day/1
+
+; this feels more lisp-y
+; maximum recursion depth reached quickly (in neb-python)
+(func increase-count-recur (inp acc)
+ (branch
+ ((eq? 0 (length (rest inp))) acc)
+ ((> (first (rest inp)) (first inp))
+ (increase-count-recur (rest inp) (+ 1 acc)))
+ (#true
+ (increase-count-recur (rest inp) acc))))
+
+; this works, but i don't like redefining variables
+(func increase-count-iter (inp)
+ (def acc 0)
+ (def prev (first inp))
+ (for-each (rest inp)
+ (if (> _item_ prev)
+ (redef acc (+ 1 acc)))
+ (redef prev _item_))
+ acc)
+
+; (a b c d e) => ((a b) (b c) (c d) (d e))
+(func pairwise (inp)
+ (zip (most inp) (rest inp)))
+
+(func abs (num)
+ (if (< num 0)
+ (* (- 1) num)
+ num))
+
+(func list-subtract (lst)
+ (def ret (apply - lst))
+ (- (/ (abs ret) ret) 1))
+
+; this algorithm is very roundabout
+(func increase-count-iter-2 (inp)
+ (abs (/ (apply + (map list-subtract (pairwise inp))) 2)))
+
+; this is the most ideomatic
+(func increase-count (inp)
+ (length
+ (filter
+ (lambda (x) (apply < x))
+ (pairwise inp))))
+
+(def lines
+ (map string->int
+ (map strip
+ (read-lines "input.txt"))))
+
+;(print (->string (increase-count-recur lines 0)))
+(print (->string (increase-count-iter lines)))
+(print (->string (increase-count-iter-2 lines)))
+(print (->string (increase-count lines)))
diff --git a/aoc/2021/day01/part2.neb b/aoc/2021/day01/part2.neb
new file mode 100644
index 0000000..31e3c99
--- /dev/null
+++ b/aoc/2021/day01/part2.neb
@@ -0,0 +1,19 @@
+; return 1 if next three greater than first three
+(func is-increasing (inp)
+ (if (< (apply + (most inp)) (apply + (rest inp)))
+ 1
+ 0))
+
+; this works, but i don't like redefining variables
+(func iter-list (inp)
+ (def acc 0)
+ (for-count (- (length inp) 3)
+ (redef acc (+ acc (is-increasing (slice inp _idx_ 4)))))
+ acc)
+
+(def lines
+ (map string->int
+ (map strip
+ (read-lines "input.txt"))))
+
+(print (->string (iter-list lines)))
diff --git a/aoc/2021/day02/input.txt b/aoc/2021/day02/input.txt
new file mode 100644
index 0000000..b7172ac
--- /dev/null
+++ b/aoc/2021/day02/input.txt
@@ -0,0 +1,6 @@
+forward 5
+down 5
+forward 8
+up 3
+down 8
+forward 2
diff --git a/aoc/2021/day02/part1.neb b/aoc/2021/day02/part1.neb
new file mode 100644
index 0000000..82201ab
--- /dev/null
+++ b/aoc/2021/day02/part1.neb
@@ -0,0 +1,44 @@
+;; https://adventofcode.com/2021/day/2
+
+; optional -- 'sum' is more visually indicative than 'apply +'
+(func sum (nums) (apply + nums))
+
+(func do-the-thing (inp)
+ ; order doesn't matter, so we can split horizontal and vertical
+ ; movement without affecting the answer
+ (def vert-changes (filter (lambda (x) (in? (first x) (list "up" "down"))) inp))
+ (def horiz-changes (filter (lambda (x) (eq? (first x) "forward")) inp))
+
+ ; turn "up"/"down" into +/- 1
+ (def vert-numbers
+ (map
+ (lambda (x)
+ (if (eq? (first x) "up")
+ (prepend (rest x) (- 1))
+ (prepend (rest x) 1)))
+ vert-changes))
+
+ (def vert
+ (sum ; add everything up
+ (map
+ (lambda (x) (* (first x) (last x))) ; multiply each pair together
+ vert-numbers)))
+
+ (def horiz
+ (sum
+ (map last horiz-changes))) ; we know there's only 2 elements in each list, and we want the last one
+
+ (print (concat "vert: " (->string vert)))
+ (print (concat "horiz: " (->string horiz)))
+ (* vert horiz))
+
+(def lines
+ (map
+ (lambda (x) (list (first x) (string->int (first (rest x))))) ; convert second values to int
+ (map
+ (lambda (x) (split x " "))
+ (map strip
+ (read-lines "input.txt")))))
+
+(print (->string lines))
+(print (->string (do-the-thing lines)))
diff --git a/aoc/2021/day03/input.txt b/aoc/2021/day03/input.txt
new file mode 100644
index 0000000..a6366a8
--- /dev/null
+++ b/aoc/2021/day03/input.txt
@@ -0,0 +1,12 @@
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010
diff --git a/aoc/2021/day03/part1.neb b/aoc/2021/day03/part1.neb
new file mode 100644
index 0000000..7ca6a08
--- /dev/null
+++ b/aoc/2021/day03/part1.neb
@@ -0,0 +1,73 @@
+;; https://adventofcode.com/2021/day/3
+
+(func one-most-common (inp)
+ (>
+ (length
+ (filter (lambda (x) (eq? "1" x)) inp))
+ (/ (length inp) 2)))
+
+; treating bits as a string of 1s and 0s
+; note: for this problem, even if neb had byte things,
+; strings would probably still be the way to go
+(func bit-flip (bitstr)
+ (join
+ (map
+ (lambda (x) (if (eq? "0" x) "1" "0"))
+ (split bitstr))
+ ""))
+
+; 'exp' or something should be in the stdlib
+(func two-n (n)
+ (branch
+ ((eq? 0 n) 1)
+ ((eq? 1 n) 2)
+ (#true
+ (* 2 (two-n (- n 1))))))
+
+(func parse-binary (bitstr)
+ (parse-binary bitstr 0 0))
+
+(func parse-binary (bitstr pos acc)
+ (if (eq? 0 (length bitstr))
+ acc
+ (block
+ (def next-int (string->int (last bitstr)))
+ (if (eq? 0 next-int)
+ (parse-binary
+ (most bitstr)
+ (+ 1 pos)
+ acc)
+ (parse-binary
+ (most bitstr)
+ (+ 1 pos)
+ (+ acc
+ (two-n pos)))))))
+ ;(* 2 pos)))))))
+
+(func do-the-thing (inp)
+ ; i don't like the def/redef pattern
+ ; this would benefit from something like "gather"
+ ; this might also work as a map/reduce?
+ (def out "")
+ (for-count (length (first inp))
+ (def one?
+ (one-most-common
+ (map
+ (lambda (x)
+ (first (slice x _idx_ 1)))
+ inp)))
+ (redef out
+ (concat out
+ (if one? "1" "0"))))
+ (print (->string
+ (*
+ (parse-binary out)
+ (parse-binary (bit-flip out)))))
+ )
+
+(def lines
+ (map split ; get all numbers as list of chars
+ (map strip
+ (read-lines "input.txt"))))
+
+(do-the-thing lines)
diff --git a/aoc/2021/day04/input.txt b/aoc/2021/day04/input.txt
new file mode 100644
index 0000000..669a51d
--- /dev/null
+++ b/aoc/2021/day04/input.txt
@@ -0,0 +1,19 @@
+7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1
+
+22 13 17 11 0
+ 8 2 23 4 24
+21 9 14 16 7
+ 6 10 3 18 5
+ 1 12 20 15 19
+
+ 3 15 0 2 22
+ 9 18 13 17 5
+19 8 7 25 23
+20 11 10 24 4
+14 21 16 12 6
+
+14 21 17 24 4
+10 16 15 9 19
+18 8 23 26 20
+22 11 13 6 5
+ 2 0 12 3 7
diff --git a/aoc/2021/day04/part01.neb b/aoc/2021/day04/part01.neb
new file mode 100644
index 0000000..49b4a7a
--- /dev/null
+++ b/aoc/2021/day04/part01.neb
@@ -0,0 +1,101 @@
+;; https://adventofcode.com/2021/day/4
+
+; good candidate for loop-acc
+(func get-all-boards (inp)
+ (def ret (list))
+ (for-count (/ (length inp) 5)
+ (redef ret (append ret
+ (get-board (slice inp (+ (* 5 (- _idx_ 1)) 1) 5)))))
+ ret)
+
+(func get-board (inp)
+ (map get-row inp))
+
+; each row is a string of items
+; separated by (potentially) several spaces
+; return a list of just the strings
+(func get-row (row)
+ (filter
+ (lambda (x)
+ (not (eq? "" x)))
+ (split row " ")))
+
+
+(func process-boards (inp)
+ (def raw-boards
+ (filter
+ (lambda (x) (not (eq? "" x)))
+ inp))
+ (get-all-boards raw-boards))
+
+(def lines
+ (map strip
+ (read-lines "input.txt")))
+
+(def moves (split (first lines) ",")) ; moves is the first line
+(def boards (process-boards (rest lines)))
+
+; this is a helper to work with zippers
+; probably good to have in the stdlib
+(func unzip (lst idx)
+ (list
+ (reverse
+ (slice lst 1 idx))
+ (slice lst (+ 1 idx))))
+
+(func has-won-row (row)
+ (apply and row))
+
+(func has-won (board moves)
+ (def checked (check-board board moves))
+ (def winner #false)
+
+ ; check rows
+ ; no break statement means we have to check everything,
+ ; even after a winner is found
+ ; can also use a while, but that would require more redefs
+ (for-each checked
+ (if (has-won-row _item_)
+ (redef winner #true)))
+
+ ; no break here means we check columns even if we won on rows
+
+ ; check columns
+ (for-count 5
+ (if (has-won-row
+ (map
+ (lambda (x) (first (slice x _idx_ 1)))
+ checked))
+ (redef winner #true)))
+
+ winner)
+
+
+(func check-board (board moves)
+ (func check-row (row)
+ (map
+ (lambda (x)
+ (in? x moves))
+ row))
+ (map check-row board))
+
+
+; how do we better iterate through this list?
+; called/next would be perfect for a zipper
+(def cur (list (list) moves)) ; init zip
+(def winner #false)
+(while (not winner)
+ (redef cur (unzip moves (+ 1 (length (first cur)))))
+ (print (->string cur))
+ (print (->string
+ (map
+ (lambda (x) (has-won x (first cur)))
+ boards)))
+ ;(def checked (check-board (first boards) (first cur)))
+ ;(print (->string checked))
+ (if (nil? (last cur))
+ (redef winner #true))
+ )
+
+(print (->string moves))
+;(print (->string (unzip moves 2)))
diff --git a/p99/p01.neb b/p99/p01.neb
new file mode 100644
index 0000000..e50cfe7
--- /dev/null
+++ b/p99/p01.neb
@@ -0,0 +1,5 @@
+; P01 Find the last box of a list.
+
+(def a (list "a" "b" "c" "d"))
+
+(print (last a))
diff --git a/p99/p02.neb b/p99/p02.neb
new file mode 100644
index 0000000..317674e
--- /dev/null
+++ b/p99/p02.neb
@@ -0,0 +1,8 @@
+; P02 - Find the last two elements of a list.
+
+(def a (list "a" "b" "c" "d"))
+
+; slice takes the index (1-based) to begin
+; and, optionally, the length of the slice
+; (when missing, will grab until the end)
+(print (->string (slice a (- (length a) 1))))
diff --git a/p99/p03.neb b/p99/p03.neb
new file mode 100644
index 0000000..05e0457
--- /dev/null
+++ b/p99/p03.neb
@@ -0,0 +1,10 @@
+; P03 - Find the K'th element of a list.
+; The first element in the list is number 1.
+
+(def a (list "a" "b" "c" "d"))
+
+(func kth (lst k)
+ (first (slice lst k 1))) ; since slice returns a list, get the element with first
+
+(print (kth a 3))
+;(kth a 8) ; panic! there is no 8th element
diff --git a/p99/p04.neb b/p99/p04.neb
new file mode 100644
index 0000000..544dc00
--- /dev/null
+++ b/p99/p04.neb
@@ -0,0 +1,5 @@
+; P04 - Find the number of elements of a list
+
+(def a (list "a" "b" "c" "d"))
+
+(print (->string (length a)))
diff --git a/p99/p05.neb b/p99/p05.neb
new file mode 100644
index 0000000..b04e329
--- /dev/null
+++ b/p99/p05.neb
@@ -0,0 +1,5 @@
+; P05 - Reverse a list
+
+(def a (list "a" "b" "c" "d"))
+
+(print (->string (reverse a)))
diff --git a/p99/p06.neb b/p99/p06.neb
new file mode 100644
index 0000000..f219058
--- /dev/null
+++ b/p99/p06.neb
@@ -0,0 +1,23 @@
+; P06 Find out whether a list is a palindrome.
+; A palindrome can be read forward or backward; e.g. (x a m a x).
+
+(def odd-good (list "x" "a" "m" "a" "x")) ; odd number of elements (good)
+(def odd-bad (list "x" "f" "m" "a" "x")) ; odd number of elements (bad)
+(def even-good (list "a" "b" "b" "a")) ; even number of elements (good)
+(def even-bad (list "a" "b" "b" "f")) ; even number of elements (bad)
+(def single (list "a")) ; single element
+(def empty (list))
+
+(func palindrome? (lst) ; by convention, funcs returning :bool end with a ?
+ (if (< (length lst) 2) ; 0 or 1 element lists are palindromic
+ #true
+ (and
+ (eq? (first lst) (last lst)) ; first element and last element are equal
+ (palindrome? (most (rest lst)))))) ; this would be clearer if slices supported negative numbers
+
+(print (->string (palindrome? odd-good)))
+(print (->string (palindrome? odd-bad)))
+(print (->string (palindrome? even-good)))
+(print (->string (palindrome? even-bad)))
+(print (->string (palindrome? single)))
+(print (->string (palindrome? empty)))
diff --git a/p99/p07.neb b/p99/p07.neb
new file mode 100644
index 0000000..9eee9ef
--- /dev/null
+++ b/p99/p07.neb
@@ -0,0 +1,57 @@
+; P07 Flatten a nested array structure.
+; Transform an array, possibly holding arrays as elements into a `flat'
+; list by replacing each array with its elements (recursively).
+
+(def a (list "a" (list "b" (list "c" "d") "e")))
+
+; this belongs in stdlib
+(func extend (lst1 lst2)
+ (reduce append lst2 lst1))
+
+; can overload functions of different arities
+(func flatten-iter (item)
+ (flatten-iter item (list)))
+
+; iterative solution
+(func flatten-iter (item acc)
+ (branch
+ ((eq? (typeof item) :[:any])
+ (if (empty? item)
+ acc
+ (flatten-iter (rest item) (extend acc (flatten-iter (first item))))))
+ (#true
+ (append acc item))))
+
+; we can also use the type system/dynamic dispatch to split up the work
+(func flatten-typ (item)
+ (flatten-typ item (list)))
+
+; non-empty lists
+(func flatten-typ (lst :{:any} acc)
+ (flatten-typ (rest lst) (extend acc (flatten-typ (first lst)))))
+
+; empty lists
+(func flatten-typ (lst :nil acc)
+ acc)
+
+; other things
+; note: we would need to know what type(s) is inside the list to avoid an
+; ambiguous definition
+;(func flatten-typ (item :string acc)
+; (append acc item))
+
+; this might be clearer/more flexible
+; maybe "not this type" should be a thing, like :![:any]
+(func not-a-list? (item)
+ (not (eq? (typeof item) :[:any])))
+
+(type :not-a-list :any not-a-list?) ; should be able to pass a lambda
+
+; this handles anything that's not a list
+(func flatten-typ (item :not-a-list acc)
+ (append acc item))
+
+(print (->string a))
+(print (->string (flatten-iter a)))
+(print (->string a))
+(print (->string (flatten-typ a)))
diff --git a/p99/p08.neb b/p99/p08.neb
new file mode 100644
index 0000000..5df816f
--- /dev/null
+++ b/p99/p08.neb
@@ -0,0 +1,57 @@
+; P08 Eliminate consecutive duplicates of list elements.
+; If a list contains repeated elements they should be replaced with a
+; single copy of the element. The order of the elements should not be changed.
+
+(def a (list "a" "a" "a" "a" "b" "c" "c" "a" "a" "d" "e" "e" "e" "e"))
+
+(func compress-iter (lst)
+ (def out (list))
+ (for-each lst
+ (if (or (empty? out)
+ (not (eq? _item_ (last out))))
+ (redef out (append out _item_))))
+ out)
+
+; use the type system/dynamic dispatch
+(func compress-typ (lst)
+ (compress-typ lst (list)))
+
+; empty lists
+(func compress-typ (lst :nil acc)
+ acc)
+
+; non-empty lists, combined with a branch
+;(func compress-typ (lst :{:any} acc)
+; (branch
+; ((empty? acc) (compress-typ (rest lst) (list (first lst))))
+; ((not (eq? (first lst) (last acc))) (compress-typ (rest lst) (append acc (first lst))))
+; (#true (compress-typ (rest lst) acc))))
+
+; non-empty lists, non-empty accumulator
+(func compress-typ (lst :{:any} acc :{:any})
+ (if (eq? (first lst) (last acc))
+ (compress-typ (rest lst) acc) ; don't append
+ (compress-typ (rest lst) (append acc (first lst)))))
+
+; non-empty lists, empty accumulator
+(func compress-typ (lst :{:any} acc :nil)
+ (compress-typ (rest lst) (list (first lst))))
+
+;(func extend (lst1 lst2)
+; (reduce append lst2 lst1))
+
+; everything is an expression, so you could do this too
+; not sure if you'd want to, though, as you're creating
+; a list and then immediately killing it, which seems
+; like it's probably wasteful in the interpreter
+;(func compress-typ (lst :{:any} acc :{:any})
+; (compress-typ (rest lst)
+; (extend
+; acc
+; (if (not (eq? (first lst) (last acc)))
+; (list (first lst))))))
+
+
+(print (->string a))
+(print (->string (compress-iter a)))
+(print (->string (compress-typ a)))
diff --git a/p99/p09.neb b/p99/p09.neb
new file mode 100644
index 0000000..619c4a4
--- /dev/null
+++ b/p99/p09.neb
@@ -0,0 +1,31 @@
+; P09 Pack consecutive duplicates of list elements into sublists.
+; If a list contains repeated elements they should be placed in separate sublists.
+
+(def a (list "a" "a" "a" "a" "b" "c" "c" "a" "a" "d" "e" "e" "e" "e"))
+
+; the list, the most recent value, the accumulator
+(func pack-dup (lst)
+ (pack-dup lst "" (list)))
+
+(func pack-dup (lst prev acc)
+ (branch
+ ((empty? lst) acc) ; if we're done, return acc
+ ((eq? (first lst) prev) ; the item is the same as the previous item
+ (pack-dup
+ (rest lst)
+ prev
+ (append ; add item to the last list in acc
+ (most acc)
+ (append
+ (last acc)
+ prev))))
+ (#true
+ (pack-dup
+ (rest lst)
+ (first lst)
+ (append
+ acc
+ (list (first lst))))))) ; add new list with this item
+
+(print (->string a))
+(print (->string (pack-dup a)))
diff --git a/p99/p10.neb b/p99/p10.neb
new file mode 100644
index 0000000..25ea1dc
--- /dev/null
+++ b/p99/p10.neb
@@ -0,0 +1,15 @@
+; P10 Run-length encoding of a list.
+; Use the result of problem P09 to implement the so-called run-length
+; encoding data compression method. Consecutive duplicates of elements
+; are encoded as arrays [N, E] where N is the number of duplicates of the
+; element E.
+
+(use "p09.neb") ; NOTE: this runs everything at this juncture, not just def/func
+
+(func encode (lst)
+ (map
+ (lambda (item)
+ (list (length item) (first item)))
+ lst))
+
+(print (->string (encode (pack-dup a))))
diff --git a/p99/p11.neb b/p99/p11.neb
new file mode 100644
index 0000000..546a7c2
--- /dev/null
+++ b/p99/p11.neb
@@ -0,0 +1,25 @@
+; P11 (*) Modified run-length encoding.
+; Modify the result of problem P10 in such a way that if an element has
+; no duplicates it is simply copied into the result list. Only elements
+; with duplicates are transferred as (N E) lists.
+
+(use "p10.neb")
+
+(func encode-modified (lst)
+ (map
+ (lambda (item)
+ (if (eq? 1 (length item))
+ (first item)
+ (list (length item) (first item))))
+ lst))
+
+(func encode-squish (lst)
+ (map
+ (lambda (item)
+ (if (eq? 1 (first item))
+ (last item)
+ item))
+ lst))
+
+(print (concat "from result of P09: " (->string (encode-modified (pack-dup a)))))
+(print (concat "from result of P10: " (->string (encode-squish (encode (pack-dup a))))))
diff --git a/p99/p12.neb b/p99/p12.neb
new file mode 100644
index 0000000..7d8ec4e
--- /dev/null
+++ b/p99/p12.neb
@@ -0,0 +1,37 @@
+; P12 Decode a run-length encoded list.
+; Given a run-length code list generated as specified in problem P11.
+; Construct its uncompressed version.
+
+(def a (list (list 4 "a") "b" (list 2 "c") (list 2 "a") "d" (list 4 "e")))
+
+(func extend (lst1 lst2)
+ (reduce append lst2 lst1))
+
+(func flatten (lst)
+ (reduce
+ (lambda (x y) (extend x y))
+ lst
+ (list)))
+
+(func decode (lst)
+ (flatten
+ (map
+ (lambda (item)
+ (if (eq? 1 (length item))
+ (list item)
+ (rpt (first item) (last item))))
+ lst)))
+
+(func rpt (cnt let)
+ (if (eq? cnt 1)
+ (list let)
+ (extend (list let) (rpt (- cnt 1) let))))
+
+; iterative
+(func rpt-iter (cnt let)
+ (def out (list))
+ (for-count cnt
+ (redef out (append out let)))
+ out)
+
+(print (->string (decode a)))
diff --git a/p99/p13.neb b/p99/p13.neb
new file mode 100644
index 0000000..e32d8cb
--- /dev/null
+++ b/p99/p13.neb
@@ -0,0 +1,30 @@
+; P13 Run-length encoding of a list (direct solution).
+; Implement the so-called run-length encoding data compression method directly.
+; I.e. don't explicitly create the sublists containing the duplicates, as in problem P09,
+; but only count them. As in problem P11, simplify the result list by replacing the
+; singleton lists (1 X) by X.
+
+(def a (list "a" "a" "a" "a" "b" "c" "c" "a" "a" "d" "e" "e" "e" "e"))
+
+(func encode-direct (lst)
+ (encode-direct lst "" (list)))
+
+(func encode-direct (lst :nil prev acc)
+ acc)
+
+(func encode-direct (lst :{:any} prev acc)
+ (if (eq? (first lst) prev)
+ (encode-direct
+ (rest lst)
+ prev
+ (append (most acc)
+ (if (list? (last acc))
+ (list (+ 1 (first (last acc))) prev)
+ (list 2 prev))))
+ (encode-direct
+ (rest lst)
+ (first lst)
+ (append acc (first lst)))))
+
+(print (->string a))
+(print (->string (encode-direct a)))
diff --git a/p99/p14.neb b/p99/p14.neb
new file mode 100644
index 0000000..5af9fc0
--- /dev/null
+++ b/p99/p14.neb
@@ -0,0 +1,15 @@
+; P14: Duplicate the elements of a list.
+
+(def a (list "a" "b" "c" "c" "d"))
+
+(func dup (lst)
+ (reduce
+ (lambda (acc item)
+ (append
+ (append acc item)
+ item))
+ lst
+ (list)))
+
+(print (->string a))
+(print (->string (dup a)))
diff --git a/p99/p15.neb b/p99/p15.neb
new file mode 100644
index 0000000..12fa8cb
--- /dev/null
+++ b/p99/p15.neb
@@ -0,0 +1,17 @@
+; P15 Replicate the elements of a list a given number of times.
+
+(def a (list "a" "b" "c"))
+
+(func repli (lst cnt)
+ (reduce
+ (lambda (acc item)
+ (def out acc)
+ (for-count cnt
+ (redef out
+ (append out item)))
+ out)
+ lst
+ (list)))
+
+(print (->string a))
+(print (->string (repli a 3)))
diff --git a/p99/p16.neb b/p99/p16.neb
new file mode 100644
index 0000000..e8fc459
--- /dev/null
+++ b/p99/p16.neb
@@ -0,0 +1,19 @@
+; P16 Drop every N'th element from a list.
+
+(def a (list "a" "b" "c" "d" "e" "f" "g" "h" "i" "k"))
+
+(func drop-n (lst n)
+ (drop-n lst n (list) n))
+
+(func drop-n (lst :nil n acc idx)
+ acc)
+
+(func drop-n (lst :{:any} n acc idx)
+ (if (eq? 1 idx)
+ (drop-n (rest lst) n acc n) ; reset n, don't add to acc
+ (drop-n (rest lst) n (append acc (first lst)) (-- idx))))
+
+(func -- (num) (- num 1))
+
+(print (->string a))
+(print (->string (drop-n a 3)))
diff --git a/p99/p17.neb b/p99/p17.neb
new file mode 100644
index 0000000..d586e87
--- /dev/null
+++ b/p99/p17.neb
@@ -0,0 +1,17 @@
+; P17 Split a list into two parts; the length of the first part is given.
+; Do not use any predefined functions.
+
+(def a (list "a" "b" "c" "d" "e" "f" "g" "h" "i" "k"))
+
+(func spl (lst idx)
+ (spl lst idx (list)))
+
+(func spl (lst idx acc)
+ (if (eq? idx 0)
+ (list acc lst)
+ (spl (rest lst) (-- idx) (append acc (first lst)))))
+
+(func -- (num) (- num 1))
+
+(print (->string a))
+(print (->string (spl a 3)))
diff --git a/p99/p18.neb b/p99/p18.neb
new file mode 100644
index 0000000..7ccf0b7
--- /dev/null
+++ b/p99/p18.neb
@@ -0,0 +1,27 @@
+; P18 Extract a slice from a list.
+; Given two indices, I and K, the slice is the list containing the elements between the
+; I'th and K'th element of the original list (both limits included). Start counting the elements with 1.
+
+(def a (list "a" "b" "c" "d" "e" "f" "g" "h" "i" "k"))
+
+(func my-slice (lst idx1 idx2)
+ (my-slice lst idx1 idx2 (list)))
+
+(func my-slice (lst :nil idx1 idx2 acc) acc)
+
+(func my-slice (lst :{:any} idx1 idx2 acc)
+ (my-slice
+ (rest lst)
+ (-- idx1)
+ (-- idx2)
+ (if
+ (or
+ (> idx1 1)
+ (< idx2 1))
+ acc
+ (append acc (first lst)))))
+
+(func -- (num) (- num 1))
+
+(print (->string a))
+(print (->string (my-slice a 3 7)))
diff --git a/p99/p19.neb b/p99/p19.neb
new file mode 100644
index 0000000..09ff324
--- /dev/null
+++ b/p99/p19.neb
@@ -0,0 +1,15 @@
+; P19 Rotate a list N places to the left.
+
+(def a (list "a" "b" "c" "d" "e" "f" "g" "h"))
+
+(func rotate (lst cnt)
+ (branch
+ ((eq? 0 cnt) lst)
+ ((> cnt 0)
+ (rotate (append (rest lst) (first lst)) (- cnt 1)))
+ ((< cnt 0)
+ (rotate (prepend (most lst) (last lst)) (+ cnt 1)))))
+
+(print (->string a))
+(print (->string (rotate a 3)))
+(print (->string (rotate a (- 2))))
diff --git a/p99/p20.neb b/p99/p20.neb
new file mode 100644
index 0000000..06b5e60
--- /dev/null
+++ b/p99/p20.neb
@@ -0,0 +1,21 @@
+; P20 Remove the K'th element from a list.
+
+(def a (list "a" "b" "c" "d"))
+
+(func enumerate (lst)
+ (def ret (list))
+ (for-each lst
+ (redef ret (append ret (list (+ 1 (length ret)) _item_))))
+ ret)
+
+(func extend (lst1 lst2)
+ (reduce append lst2 lst1))
+
+; using slices
+(func remove-at-slice (lst idx)
+ (extend
+ (slice lst 1 (- idx 1))
+ (slice lst (+ idx 1))))
+
+(print (->string a))
+(print (->string (remove-at-slice a 2)))
diff --git a/p99/p21.neb b/p99/p21.neb
new file mode 100644
index 0000000..8b465e9
--- /dev/null
+++ b/p99/p21.neb
@@ -0,0 +1,16 @@
+; P21 Insert an element at a given position into a list
+
+(def a (list "a" "b" "c" "d"))
+
+(func extend (lst1 lst2)
+ (reduce append lst2 lst1))
+
+(func insert-at (item lst idx)
+ (extend
+ (slice lst 1 (- idx 1))
+ (prepend (slice lst idx) item)))
+ ;(slice lst idx)
+ ;(append (slice lst 1 (- idx 1)) item)))
+
+(print (->string a))
+(print (->string (insert-at "f" a 2)))
diff --git a/rosetta/factors-of-int.neb b/rosetta/factors-of-int.neb
new file mode 100644
index 0000000..54115bd
--- /dev/null
+++ b/rosetta/factors-of-int.neb
@@ -0,0 +1,41 @@
+(func .list-of-num (num)
+ (def nums (list))
+ (for-count num
+ (redef nums (append nums _idx_)))
+ nums)
+
+(func .rough-sqrt (num) (.rough-sqrt num 1))
+
+(func .rough-sqrt (num val)
+ (branch
+ ((eq? (* val val) num) val)
+ ((> (* val val) num) (- val 1))
+ (#true
+ (.rough-sqrt num (+ 1 val)))))
+
+(func factor-naive (num)
+ (filter (lambda (x) (int? (/ num x))) (.list-of-num num)))
+
+(func factor-better (num)
+ (append
+ (filter (lambda (x) (int? (/ num x))) (.list-of-num (floor (/ num 2))))
+ num))
+
+(func factor-even-better (num)
+ (def ret (list))
+ (for-each (.list-of-num (.rough-sqrt num))
+ (if (int? (/ num _item_))
+ (redef ret (append ret (list _item_ (/ num _item_))))))
+ ret)
+
+(func factors (num)
+ (filter
+ (lambda (x)
+ (int? (/ num x)))
+ (.list-of-num (.rough-sqrt num))))
+
+(func factor-pairs (num)
+ (map
+ (lambda (x)
+ (list x (/ num x)))
+ (factors num)))
diff --git a/rosetta/lev.neb b/rosetta/lev.neb
new file mode 100644
index 0000000..6797c41
--- /dev/null
+++ b/rosetta/lev.neb
@@ -0,0 +1,20 @@
+(func min (lst :{:int})
+ (def val (first lst))
+ (for-each (rest lst)
+ (if (< _item_ val)
+ (redef val _item_)))
+ val)
+
+(func lev (s t)
+ (branch
+ ((eq? 0 (length s)) (length t))
+ ((eq? 0 (length t)) (length s))
+ ((eq? (first s) (first t))
+ (lev (rest s) (rest t)))
+ (#true
+ (+ 1
+ (min
+ (list
+ (lev s (rest t))
+ (lev (rest s) t)
+ (lev (rest s) (rest t))))))))
diff --git a/rosetta/lines.neb b/rosetta/lines.neb
new file mode 100644
index 0000000..45a6a6f
--- /dev/null
+++ b/rosetta/lines.neb
@@ -0,0 +1,16 @@
+
+(func adjust (text width)
+ (def lines (list))
+ (def word "")
+ (for-each (split text " ")
+ (branch
+ ((eq? 0 (length word)) (redef word _item_))
+ ((<= (+ (length word) 1 (length _item_)) width)
+ (redef word (concat word " " _item_)))
+ (#true
+ (block
+ (redef lines (append lines word))
+ (redef word _item_)))))
+ (if (not (eq? 0 (length word)))
+ (append lines word)
+ lines))
diff --git a/rosetta/luhn.neb b/rosetta/luhn.neb
new file mode 100644
index 0000000..ac06e17
--- /dev/null
+++ b/rosetta/luhn.neb
@@ -0,0 +1,73 @@
+(func odd-elems (lst)
+ (odd-elems lst (list)))
+
+(func odd-elems (lst acc)
+ (if (eq? 0 (length lst))
+ acc
+ (odd-elems (rest (rest lst)) (append acc (first lst)))))
+
+(func even-elems (lst)
+ (even-elems lst (list)))
+
+(func even-elems (lst acc)
+ (if (>= 1 (length lst))
+ acc
+ (even-elems (rest (rest lst)) (append acc (first (rest lst))))))
+
+(func luhn? (num)
+ ;; algo:
+ ;; with digits reversed, sum odd digits
+ ;; for all even digits:
+ ;; - double them
+ ;; - sum the digits (i.e. 16 -> 1 + 6 -> 7)
+ ;; - sum everything
+ ;; sum both values, and if the result ends in 0, it's valid
+ (def reverse-digits (reverse (->string num)))
+ ; sum the odd digits
+ (def s1
+ (reduce
+ (lambda (x y) (+ x (string->int y)))
+ (odd-elems reverse-digits) 0))
+ (def s2
+ ; sum everything
+ (reduce (lambda (x y) (+ x y))
+ ; sum each of the digits
+ (map (lambda (x) (apply + x))
+ ; split the resulting numbers into digits
+ (map (lambda (x) (map string->int (split (->string x))))
+ ; double the even digits
+ (map (lambda (x) (* 2 (string->int x)))
+ (even-elems reverse-digits)))) 0))
+ (int? (/ (+ s1 s2) 10)))
+
+(func base36-to-base10 (value :string)
+ (base36-to-base10 (ord value)))
+
+(func base36-to-base10 (value :int)
+ (if (< value 32)
+ (+ 9 value)
+ (base36-to-base10 (- value 32))))
+
+(func isin? (value)
+ ;; algo:
+ ;; - must be 12 digits
+ ;; - first 2 must be letters
+ ;; - last must be a number
+ ;; - interpret all values as base 32
+ ;; - replace them as if replacing characters in a string
+ ;; - run luhn
+ (def digits (split "0123456789"))
+ (and
+ (eq? 12 (length value))
+ (not (in? (first value) digits))
+ (not (in? (first (rest value)) digits))
+ (in? (last value) digits)
+ (luhn? (string->int
+ (apply concat
+ (reduce
+ (lambda (acc val)
+ (append acc
+ (->string (try
+ (string->int val)
+ (base36-to-base10 val)))))
+ (split value) (list)))))))
diff --git a/rosetta/palindrome.neb b/rosetta/palindrome.neb
new file mode 100644
index 0000000..198456d
--- /dev/null
+++ b/rosetta/palindrome.neb
@@ -0,0 +1,6 @@
+(func palindrome? (str)
+ (branch
+ ((<= (length str) 1) #true)
+ ((eq? (first str) (last str))
+ (palindrome? (reverse (rest (reverse (rest str))))))
+ (#true #false)))
diff --git a/rosetta/sum-of-squares.neb b/rosetta/sum-of-squares.neb
new file mode 100644
index 0000000..be76194
--- /dev/null
+++ b/rosetta/sum-of-squares.neb
@@ -0,0 +1,2 @@
+(func sum-of-squares (lst :[:int])
+ (reduce + (map (lambda (x) (* x x)) lst) 0))
generated by cgit v1.2.3 (git 2.39.1) at 2025-10-29 16:30:50 +0000