Fibonacci word/fractal: Difference between revisions

=={{header|jq}}==

{{works with|jq}}

'''Also works with gojq, the Go implementation of jq, and with fq.'''

The SVG output is suitable for viewing in a browser.

<syntaxhighlight lang=jq>

def max(s): reduce s as $x (-infinite; if $x > . then $x else . end);

def min(s): reduce s as $x ( infinite; if $x < . then $x else . end);

# An unbounded stream

def fibonacci_words:

"1",

(["0","1"] | recurse( [add, .[0]]) | .[0]);

def turnLeft:

{"R": "U",

"U": "L",

"L": "D",

"D": "R"};

def turnRight:

{"R": "D",

"D": "L",

"L": "U",

"U": "R"};

# Input: the remaining Fibonacci word

# $n should initially be 1 and represents

# 1 plus the count of the letters already processed.

#

# Emit a stream of single-letter directions ("1" for forward),

# namely, if current char is 0

# - turn left if $n is even

# - turn right if $n is odd

def directions($n):

if length == 0 then empty

else .[0:1] as $c

| (if $c == "0"

then if $n % 2 == 0 then "L" else "R" end

else "1"

end),

(.[1:] | directions($n+1))

end;

# $current is the direction in which we are currently pointing.

# output: the direction in which the next step should be taken

def next_step($current; $turn):

if $turn == "1" then $current

elif $turn == "L" then turnLeft[$current]

elif $turn == "R" then turnRight[$current]

else error

end;

# input: a Fibonacci word

# output: a stream of directions for turning, or "1" for not turning,

# i.e. a stream of: U, D, L, R, or 1

# Initially, we are facing R

def steps:

foreach directions(1) as $turn ("R";

next_step(.; $turn) );

# output a stream of [x,y] co-ordinates corresponding to the specified

# stream of steps of the given size.

# So we could for example call: points( nth(5; fibonacci_words) | steps; $size)

def points(steps; $size):

foreach steps as $step ([0,0];

. as [$x, $y]

| if $step == "R" then [$x + $size, $y]

elif $step == "D" then [$x, $y + $size]

elif $step == "L" then [$x - $size, $y]

elif $step == "U" then [$x, $y - $size]

else error

end );

# svg header boilerplate

# viewBox = '<min-x> <min-y> <width> <height>'

def svg($minX; $minY; $width; $height):

"<?xml version='1.0' standalone='no'?>",

"<!DOCTYPE svg PUBLIC '-//W3C//DTD SVG 1.1//EN' 'http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd'>",

"<svg viewBox='\($minX - 10) \($minY - 10) \($width + 20) \($height + 20)' version='1.1' xmlns='http://www.w3.org/2000/svg'>";

# input: array of [x,y] co-ordinates

# output: "<polyline .... />"

def polyline:

{a:1, b:1} as $p

| "<polyline points='\(map(join(","))|join(" "))'",

" style='fill:none; stroke:black; stroke-width:1' transform='translate(\($p.a), \($p.b))' />";

# Output the svg for the $n-th Fibonacci word counting from 0

def fibonacci_word_svg($n):

[points( nth($n; fibonacci_words) | steps; 10)]

| min( .[] | .[0]) as $minx

| max( .[] | .[0]) as $maxx

| min( .[] | .[1]) as $miny

| max( .[] | .[1]) as $maxy

| (($maxx-$minx)|length) as $width

| (($maxy-$miny)|length) as $height

| svg( $minx; $miny; $width; $height),

polyline,

"</svg>" ;

fibonacci_word_svg(22) # the Rust entry uses 22

</syntaxhighlight>

{{output}}

Essentially as for [[#Rust|Rust]] - [[Media:Fibword_fractal_rust.svg]]