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{{SVG 600 600}
 {g {AXES 600 600}
  {polyline
   {@ points="{S.map {superellipse 200 100 4} 
                     {S.serie -1 1.01 0.01}}"
      {stroke #f00 4}}}
  {polyline
   {@ points="{S.map {superellipse 100 200 0.5} 
                     {S.serie -1 1.01 0.01}}"
      {stroke #0f0 4}}}
  {polyline
   {@ points="{S.map {superellipse 200 200 1} 
                     {S.serie -1 1.01 0.01}}"
      {stroke #888 2}}}
  {polyline
   {@ points="{S.map {superellipse 200 200 2} 
                     {S.serie -1 1.01 0.01}}"
      {stroke #888 2}}}
}}
_h1 superellipse (x/a){sup n}+(y/b){sup n}=1

_p Following [[rosettacode.org|https://rosettacode.org/wiki/Superellipse#Lambdatalk]] draw a superellipse with n = 2.5, and a = b = 200.
{pre

'{def superellipse
 {def sgn {lambda {:n} {if {< :n 0} then - else +}}}

{lambda {:a :b :n :t}
  {let { {:a :a} {:b :b} {:n {/ 2 :n}}
         {:cost {cos {* {PI} :t}}}
         {:sint {sin {* {PI} :t}}}
       } {sgn :cost}{* :a {pow {abs :cost} :n}}
         {sgn :sint}{* :b {pow {abs :sint} :n}}
}}} 
-> {def superellipse
 {def sgn {lambda {:n} {if {< :n 0} then - else +}}}

_p We use {b SVG} and the [[lib_plot]] library defining the {b SVG, AXES, stroke} functions to draw 4 superellipses, a rounded rectangle, a circle and a square.
{pre
'{{SVG 600 600}
 {g {AXES 600 600}
  {polyline
   {@ points="{S.map {superellipse 200 300 2.5} {S.serie -1 1.01 0.01}}"
      {stroke #f00 4}}}
  {polyline
   {@ points="{S.map {superellipse 100 200 0.5} {S.serie -1 1.01 0.01}}"
      {stroke #0f0 4}}}
  {polyline
   {@ points="{S.map {superellipse 200 200 1.0} {S.serie -1 1.01 0.01}}"
      {stroke #888 2}}}
  {polyline
   {@ points="{S.map {superellipse 200 200 2.0} {S.serie -1 1.01 0.01}}"
      {stroke #888 2}}}
}}
}

{{hide}
{def SVG 
 {lambda {:w :h}
  svg {@ width=":wpx" height=":hpx"
         style="background:#eee; margin-left:-10px;"}
}}

{def AXES 
 {lambda {:w :h}
  {@ transform="translate({/ :w 2} {/ :h 2}) scale(1,-1)"}

{S.map {{lambda {:w :h :i} 
         {line {@ x1="-{/ :w 2}" y1=":i" x2="{/ :w 2}" y2=":i"
               {stroke #f008" 1}}}
         {text {@ x="0" y=":i" transform="rotate(180) scale(-1,1)"}
               {round {/ :i -10}}}
         } :w :h} {S.serie -:h :h {/ :h {/ :h 50}}}}

{S.map {{lambda {:w :h :i}
         {line {@ x1=":i" y1="-{/ :h 2}" x2=":i" y2="{/ :h 2}" 
               {stroke #0f08" 1}}}
         {text {@ x=":i" y="0" transform="rotate(0) scale(1,-1)"}
               {round {/ :i 10}}} 
         } :w :h} {S.serie -:w :w {/ :w {/ :w 50}}}}

{line {@ x1="-{/ :w 2}" y1="0" x2="{/ :w 2}" y2="0"
           {stroke #f00 3}}}

{line {@ x1="0" y1="-{/ :h 2}" x2="0" y2="{/ :h 2}"
           {stroke #0f0 3}}}  
}}

{def stroke
 {lambda {:col :w}
         stroke=":col" 
         fill="transparent"
         stroke-width=":w" 
}}
}