Discussion on lobsters too: https://lobste.rs/s/ydxus1/pipelining_might_be_my_favorite
A bit from the readme appreciating concatenative programming:
The Joy language introduced concatenative functional programming. This generally means a stack based virtual machine, and a program consisting of words which are functions taking an input stack and returning an output stack. The natural syntax that results is postfix. Over a very long time I have come to feel that syntax gets in between me and the power in a language. Postfix is the least syntax possible.
There are several reasons I like the concatenative style of programming:
-
Function composition is concatenation.
-
Pipelining values through functions to get new values is the most natural idiom.
-
Functions are applied from left to right instead of inside out.
-
Support for multiple return values comes for free.
-
No need for operator precedence.
-
Fewer delimiters are required:
- Parentheses are not needed to control operator precedence.
- Semicolons are not needed to separate statements.
- Commas are not needed to separate arguments.
(Note: Sapf is inspired by, but is not purely a concatenative language because it has lexical variables.)
When I am programming interactively, I most often find myself in the situation where I have a value and I want to transform it to something else. The thing to do is apply a function with some parameters. With concatenative programming this is very natural. You string along several words and get a new value.
The given Uiua example (mercifully given using words rather than the symbols):
[3 4 5 10 23]
divide length on /+
For all the talk about "forward" it's uncomfortable to me how the Uiua evaluation within a line happens backward.
An equivalent in Factor, where keep is close to on:
{ 3 4 5 10 23 }
[ sum ] keep length /
But this pattern of doing two things in sequence to the same item is common enough that bi is handy:
{ 3 4 5 10 23 }
[ sum ] [ length ] bi /
Day 6
spoiler
: get-input ( -- rows )
"vocab:aoc-2024/06/input.txt" utf8 file-lines ;
: all-locations ( rows -- pairs )
dimension <coordinate-matrix> concat ;
: guard-location ( rows -- pair )
[ all-locations ] keep
'[ _ matrix-nth "<>^v" in? ] find nip ;
TUPLE: state location char ;
C: <state> state
: guard-state ( rows -- state )
[ guard-location ]
[ dupd matrix-nth ] bi <state> ;
: faced-location ( state -- pair )
[ char>> H{
{ CHAR: > { 0 1 } }
{ CHAR: v { 1 0 } }
{ CHAR: < { 0 -1 } }
{ CHAR: ^ { -1 0 } }
} at ] [ location>> ] bi v+ ;
: off-grid? ( rows location -- ? )
[ dimension ] dip
[ v<= vany? ] keep
{ 0 0 } v< vany? or ;
: turn ( state -- state' )
[ location>> ] [ char>> ] bi
H{
{ CHAR: > CHAR: v }
{ CHAR: v CHAR: < }
{ CHAR: < CHAR: ^ }
{ CHAR: ^ CHAR: > }
} at <state> ;
: obstacle? ( rows location -- ? )
swap matrix-nth CHAR: # = ;
: guard-step ( rows state -- state' )
swap over faced-location
{
{ [ 2dup off-grid? ] [ 2nip f <state> ] }
{ [ [ obstacle? ] keep-under ] [ drop turn ] }
[ swap char>> <state> ]
} cond ;
: walk-out ( rows state -- trail )
[
[ 2dup location>> off-grid? ] [
dup location>> ,
dupd guard-step
] until
] { } make 2nip ;
: part1 ( -- n )
get-input dup guard-state walk-out cardinality ;
: (walk-loops?) ( visited rows state -- looped? )
dupd guard-step
2dup location>> off-grid? [ 3drop f ] [
pick dupd in? [ 3drop t ] [
pick dupd adjoin (walk-loops?)
] if
] if ;
: walk-loops? ( rows -- looped? )
dup guard-state
[ HS{ } clone ] 2dip
pick dupd adjoin (walk-loops?) ;
: obstacle-candidates ( rows -- pairs )
[ guard-location ]
[ dup guard-state walk-out members ] bi remove ;
: part2 ( -- n )
get-input dup obstacle-candidates
[ CHAR: # spin deep-clone [ matrix-set-nth ] keep walk-loops? ] with count ;
Slow and dumb gets it done! I may revisit this when I give up on future days.
Factor
spoiler
TUPLE: equation value numbers ;
C: <equation> equation
: get-input ( -- equations )
"vocab:aoc-2024/07/input.txt" utf8 file-lines [
split-words unclip but-last string>number
swap [ string>number ] map <equation>
] map ;
: possible-quotations ( funcs numbers -- quots )
dup length 1 -
swapd all-selections
[ unclip swap ] dip
[ zip concat ] with map
swap '[ _ prefix >quotation ] map ;
: possibly-true? ( funcs equation -- ? )
[ numbers>> possible-quotations ] [ value>> ] bi
'[ call( -- n ) _ = ] any? ;
: solve ( funcs -- n )
get-input
[ possibly-true? ] with filter
[ value>> ] map-sum ;
: part1 ( -- n )
{ + * } solve ;
: _|| ( m n -- mn )
[ number>string ] bi@ append string>number ;
: part2 ( -- n )
{ + * _|| } solve ;
Nothing smart to see here. I may revisit this when I give up on future days.
Factor
spoiler
: get-input ( -- rows )
"vocab:aoc-2024/06/input.txt" utf8 file-lines ;
: all-locations ( rows -- pairs )
dimension <coordinate-matrix> concat ;
: guard-location ( rows -- pair )
[ all-locations ] keep
'[ _ matrix-nth "<>^v" in? ] find nip ;
TUPLE: state location char ;
C: <state> state
: guard-state ( rows -- state )
[ guard-location ]
[ dupd matrix-nth ] bi <state> ;
: faced-location ( state -- pair )
[ char>> H{
{ CHAR: > { 0 1 } }
{ CHAR: v { 1 0 } }
{ CHAR: < { 0 -1 } }
{ CHAR: ^ { -1 0 } }
} at ] [ location>> ] bi v+ ;
: off-grid? ( rows location -- ? )
[ dimension ] dip
[ v<= vany? ] keep
{ 0 0 } v< vany? or ;
: turn ( state -- state' )
[ location>> ] [ char>> ] bi
H{
{ CHAR: > CHAR: v }
{ CHAR: v CHAR: < }
{ CHAR: < CHAR: ^ }
{ CHAR: ^ CHAR: > }
} at <state> ;
: obstacle? ( rows location -- ? )
swap matrix-nth CHAR: # = ;
: guard-step ( rows state -- state' )
swap over faced-location
{
{ [ 2dup off-grid? ] [ 2nip f <state> ] }
{ [ [ obstacle? ] keep-under ] [ drop turn ] }
[ swap char>> <state> ]
} cond ;
: walk-out ( rows state -- trail )
[
[ 2dup location>> off-grid? ] [
dup location>> ,
dupd guard-step
] until
] { } make 2nip ;
: part1 ( -- n )
get-input dup guard-state walk-out cardinality ;
: (walk-loops?) ( visited rows state -- looped? )
dupd guard-step
2dup location>> off-grid? [ 3drop f ] [
pick dupd in? [ 3drop t ] [
pick dupd adjoin (walk-loops?)
] if
] if ;
: walk-loops? ( rows -- looped? )
dup guard-state
[ HS{ } clone ] 2dip
pick dupd adjoin (walk-loops?) ;
: obstacle-candidates ( rows -- pairs )
[ guard-location ]
[ dup guard-state walk-out members ] bi remove ;
: part2 ( -- n )
get-input dup obstacle-candidates
[ CHAR: # spin deep-clone [ matrix-set-nth ] keep walk-loops? ] with count ;
Day 5
spoiler
: get-input ( -- rules updates )
"vocab:aoc-2024/05/input.txt" utf8 file-lines
{ "" } split1
"|" "," [ '[ [ _ split ] map ] ] bi@ bi* ;
: relevant-rules ( rules update -- rules' )
'[ [ _ in? ] all? ] filter ;
: compliant? ( rules update -- ? )
[ relevant-rules ] keep-under
[ [ index* ] with map first2 < ] with all? ;
: middle-number ( update -- n )
dup length 2 /i nth-of string>number ;
: part1 ( -- n )
get-input
[ compliant? ] with
[ middle-number ] filter-map sum ;
: compare-pages ( rules page1 page2 -- <=> )
[ 2array relevant-rules ] keep-under
[ drop +eq+ ] [ first index zero? +gt+ +lt+ ? ] if-empty ;
: correct-update ( rules update -- update' )
[ swapd compare-pages ] with sort-with ;
: part2 ( -- n )
get-input dupd
[ compliant? ] with reject
[ correct-update middle-number ] with map-sum ;
Factor
: get-input ( -- rules updates )
"vocab:aoc-2024/05/input.txt" utf8 file-lines
{ "" } split1
"|" "," [ '[ [ _ split ] map ] ] bi@ bi* ;
: relevant-rules ( rules update -- rules' )
'[ [ _ in? ] all? ] filter ;
: compliant? ( rules update -- ? )
[ relevant-rules ] keep-under
[ [ index* ] with map first2 < ] with all? ;
: middle-number ( update -- n )
dup length 2 /i nth-of string>number ;
: part1 ( -- n )
get-input
[ compliant? ] with
[ middle-number ] filter-map sum ;
: compare-pages ( rules page1 page2 -- <=> )
[ 2array relevant-rules ] keep-under
[ drop +eq+ ] [ first index zero? +gt+ +lt+ ? ] if-empty ;
: correct-update ( rules update -- update' )
[ swapd compare-pages ] with sort-with ;
: part2 ( -- n )
get-input dupd
[ compliant? ] with reject
[ correct-update middle-number ] with map-sum ;
Factor
spoiler
: get-input ( -- rows )
"vocab:aoc-2024/04/input.txt" utf8 file-lines ;
: verticals ( rows -- lines )
[ dimension last [0..b) ] keep cols ;
: slash-origins ( rows -- coords )
dimension
[ first [0..b) [ 0 2array ] map ] [
first2 [ 1 - ] [ 1 (a..b] ] bi*
[ 2array ] with map
] bi append ;
: backslash-origins ( rows -- coords )
dimension first2
[ [0..b) [ 0 2array ] map ]
[ 1 (a..b] [ 0 swap 2array ] map ] bi* append ;
: slash ( rows origin -- line )
first2
[ 0 [a..b] ]
[ pick dimension last [a..b) ] bi* zip
swap matrix-nths ;
: backslash ( rows origin -- line )
[ dup dimension ] dip first2
[ over first [a..b) ]
[ pick last [a..b) ] bi* zip nip
swap matrix-nths ;
: slashes ( rows -- lines )
dup slash-origins
[ slash ] with map ;
: backslashes ( rows -- lines )
dup backslash-origins
[ backslash ] with map ;
: word-count ( line word -- n )
dupd [ reverse ] dip
'[ _ subseq-indices length ] bi@ + ;
: part1 ( -- n )
get-input
{ [ ] [ verticals ] [ slashes ] [ backslashes ] } cleave-array concat
[ "XMAS" word-count ] map-sum ;
: origin-adistances ( rows origins line-quot: ( rows origin -- line ) -- origin-adistances-assoc )
with zip-with
"MAS" "SAM" [ '[ [ _ subseq-indices ] map-values ] ] bi@ bi append
harvest-values
[ [ 1 + ] map ] map-values ; inline
: a-coords ( origin-adistances coord-quot: ( adistance -- row-delta col-delta ) -- coords )
'[ first2 [ @ 2array v+ ] with map ] map-concat ; inline
: slash-a-coords ( rows -- coords )
dup slash-origins [ slash ] origin-adistances
[ [ 0 swap - ] keep ] a-coords ;
: backslash-a-coords ( rows -- coords )
dup backslash-origins [ backslash ] origin-adistances
[ dup ] a-coords ;
: part2 ( -- n )
get-input [ slash-a-coords ] [ backslash-a-coords ] bi
intersect length ;
Better viewed on GitHub.
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A bigger discussion on Hacker News: https://news.ycombinator.com/item?id=43751076