Category talk:Jq-turtle

turtle.jq - turtle graphics with some ancillary SVG convenience functions.

To include these turtle graphics definitions, download the page contents (minus this preamble) into a file and include it using an appropriate `include` directive, e.g.

include "turtle" {search: "."};

# The turtle's state: {svg, up, angle}

# Angle:
# => =   0 degrees
# ^  =  90 degrees
# <= = 180 degrees
# v  = 270 degrees

def pi: 4 * (1|atan);
def a2radians: 2 * pi * ./360;
def cosDegrees: a2radians|cos;
def sinDegrees: a2radians|sin;

# $start : [$x, $y]
def turtle($start):
  $start
  | if type == "array" then "M \($start|join(","))" else "M 0,0" end
  | {svg: ., up:true, angle:0};

def turtleUp: .up=true;
def turtleDown: .up=false;

def turtleRotate($angle): .angle = (360 + (.angle + $angle)) % 360;

def turtleArcRight($r):
       if   .angle==  0 then .svg += " a\($r),\($r) 0 0 1 \($r),\($r)"  # checked
       elif .angle== 90 then .svg += " a\($r),\($r) 0 0 1 \($r),-\($r)" # checked
       elif .angle==180 then .svg += " a\($r),\($r) 0 0 1 -\($r),-\($r)" # checked
       elif .angle==270 then .svg += " a\($r),\($r) 0 0 1 -\($r),\($r)" # checked
       else "turtleArcRight at \(.angle) not yet supported" | error
       end
       | turtleRotate(-90);

def turtleArcLeft($r):
       if   .angle==  0 then .svg += " a\($r),\($r) 0 0 0 \($r),-\($r)" # check
       elif .angle== 90 then .svg += " a\($r),\($r) 0 0 0 -\($r),-\($r)" # check
       elif .angle==180 then .svg += " a\($r),\($r) 0 0 0 -\($r),\($r)" # check
       elif .angle==270 then .svg += " a\($r),\($r) 0 0 0 \($r),\($r)"
       else "turtleArcRight at \(.angle) not yet supported" | error
       end
       | turtleRotate(90);

def turtleForward($d):
  def rnd: 1000*.|round/1000;
  if .up
  then if   .angle==  0 then .svg += " m \($d),0"
       elif .angle== 90 then .svg += " m 0,-\($d)"
       elif .angle==180 then .svg += " m -\($d),0"
       elif .angle==270 then .svg += " m 0,\($d)"
       else ($d * (.angle|cosDegrees)) as $dx
       |    ($d * (.angle|sinDegrees) * -1) as $dy
       | .svg += " m\($dx),\($dy)"
       end
  else if   .angle==  0 then .svg += " h \($d)"
       elif .angle== 90 then .svg += " v -\($d)"
       elif .angle==180 then .svg += " h -\($d)"
       elif .angle==270 then .svg += " v \($d)"
       else ($d * (.angle|cosDegrees|rnd)) as $dx
       |    ($d * (.angle|sinDegrees|rnd) * -1) as $dy
       | .svg += " l\($dx),\($dy)"
       end
  end;

def svg($size):
  "<svg viewBox=\"0 0 \($size) \($size)\" xmlns=\"http://www.w3.org/2000/svg\">",
  .,
 "</svg>";

def path($fill; $stroke; $width):
  "<path fill=\"\($fill)\" stroke=\"\($stroke)\" stroke-width=\"\($width)\" d=\"\(.svg)\" />";

def draw($size):
  path("none"; "red"; 1) | svg($size);

###

def svg($size):
  "<svg viewBox=\"0 0 \($size) \($size)\" xmlns=\"http://www.w3.org/2000/svg\">",
  .,
  "</svg>";
  
def path($fill; $stroke; $width):
  "<path fill=\"\($fill)\" stroke=\"\($stroke)\" stroke-width=\"1\" d=\"\(.svg)\" />";

def draw($size):
  path("none"; "red"; 1) | svg($size) ;