"Hello, world!" in Piet

Program

  Original code           Visualization
 (codel size 11)

Design Goals

For decorativeness the image should appear symmetrical. Preferably
no color block other than the black ones should be greater than one
codel. Nevertheless the image should be as small as possible. 

Implementation

Program flow follows a spiral ending in the black cage in the center.
Some needless additional code was added to stretch the spiral path,
which was necessary to prevent adjacent codels from having the same
color. Fortunately that also caused the code terminating exactly in
the black center.

In the visualization above non-coding codels are colored black.
Program flow is shown as a black line. The position of additional
code is marked by black squares.

Commands

Since the color blocks are not greater than one codel some stack
tricks are needed to put large numbers on the stack and to avoid
defining the same character more than once. 

out:    character output ("SP" = space, "\n" = newline)
cmd:    command (abbr.), "out" = "out(char)"
stack:  stack after execution of the adjoining command
blue:   additional commands, acting as NOP
red:    sequence "pus, poi" to rotate the DP at the edges of the spiral
brown:  comment

--- --- ---------------------------------------------------------------
out cmd stack ==>
--- --- ---------------------------------------------------------------
    swi
    pus   1
    pus   1   1
    add   2
    dup   2   2
    dup   2   2   2
    add   2   4
    mul   8
    dup   8   8
    dup   8   8   8
    pus   8   8   8   1
    poi   8   8   8
    dup   8   8   8   8
    mul   8   8  64
    add   8  72
 H  out   8
    pus   8   1
    pus   8   1   1
    add   8   2
    add  10                             // newline for later use
    dup  10  10
    dup  10  10  10
    pus  10  10  10   1
    poi  10  10  10
    mul  10 100                         // 100 for later use ("d", "!")
    dup  10 100 100
    pus  10 100 100   1
    add  10 100 101
 e  out  10 100
    dup  10 100 100
    pus  10 100 100   1
    pus  10 100 100   1   1
    add  10 100 100   2
    pus  10 100 100   2   1
    poi  10 100 100   2
    dup  10 100 100   2   2
    dup  10 100 100   2   2   2
    add  10 100 100   2   4
    mul  10 100 100   8
    add  10 100 108                     // 108 = "l" in "world"
    dup  10 100 108 108
    dup  10 100 108 108 108
    dup  10 100 108 108 108 108
 l  out  10 100 108 108 108
    pus  10 100 108 108 108   1
    poi  10 100 108 108 108
 l  out  10 100 108 108
    pus  10 100 108 108   1
    pus  10 100 108 108   1   1
    add  10 100 108 108   2
    pus  10 100 108 108   2   1
    add  10 100 108 108   3
    pus  10 100 108 108   3   1
    pop  10 100 108 108   3
    pus  10 100 108 108   3   1
    poi  10 100 108 108   3
    dup  10 100 108 108   3   3
    dup  10 100 108 108   3   3   3
    pus  10 100 108 108   3   3   3   1
    pus  10 100 108 108   3   3   3   1   1
    add  10 100 108 108   3   3   3   2
    rol  10 100 108   3   3 108
    add  10 100 108   3 111             // 3 + 111 = "r" in "world"
    dup  10 100 108   3 111 111         // 111 = "o" in "world"
    pus  10 100 108   3 111 111   1
    poi  10 100 108   3 111 111
    dup  10 100 108   3 111 111 111
 o  out  10 100 108   3 111 111
    dup  10 100 108   3 111 111 111     // 111 + 8 = "w" in "world"
    pus  10 100 108   3 111 111 111   1
    pus  10 100 108   3 111 111 111   1   1
    pus  10 100 108   3 111 111 111   1   1   1
    pop  10 100 108   3 111 111 111   1   1
    pus  10 100 108   3 111 111 111   1   1   1
    poi  10 100 108   3 111 111 111   1   1
    pus  10 100 108   3 111 111 111   1   1   1
    pop  10 100 108   3 111 111 111   1   1
    add  10 100 108   3 111 111 111   2
    dup  10 100 108   3 111 111 111   2   2
    dup  10 100 108   3 111 111 111   2   2   2
    add  10 100 108   3 111 111 111   2   4
    dup  10 100 108   3 111 111 111   2   4   4
    pus  10 100 108   3 111 111 111   2   4   4   1
    poi  10 100 108   3 111 111 111   2   4   4
    dup  10 100 108   3 111 111 111   2   4   4   4
    mul  10 100 108   3 111 111 111   2   4  16
    dup  10 100 108   3 111 111 111   2   4  16  16
    add  10 100 108   3 111 111 111   2   4  32        // 32 = "SP"
    dup  10 100 108   3 111 111 111   2   4  32  32  
    pus  10 100 108   3 111 111 111   2   4  32  32   1
    pus  10 100 108   3 111 111 111   2   4  32  32   1   1
    poi  10 100 108   3 111 111 111   2   4  32  32   1
    pus  10 100 108   3 111 111 111   2   4  32  32   1   1
    add  10 100 108   3 111 111 111   2   4  32  32   2
    dup  10 100 108   3 111 111 111   2   4  32  32   2   2
    add  10 100 108   3 111 111 111   2   4  32  32   4
    dup  10 100 108   3 111 111 111   2   4  32  32   4   4
    dup  10 100 108   3 111 111 111   2   4  32  32   4   4   4
    pus  10 100 108   3 111 111 111   2   4  32  32   4   4   4   1
    poi  10 100 108   3 111 111 111   2   4  32  32   4   4   4
    add  10 100 108   3 111 111 111   2   4  32  32   4   8
    add  10 100 108   3 111 111 111   2   4  32  32  12
    add  10 100 108   3 111 111 111   2   4  32  44
 ,  out  10 100 108   3 111 111 111   2   4  32
 SP out  10 100 108   3 111 111 111   2   4
    pus  10 100 108   3 111 111 111   2   4   1
    poi  10 100 108   3 111 111 111   2   4
    mul  10 100 108   3 111 111 111   8
    add  10 100 108   3 111 111 119
 w  out  10 100 108   3 111 111
 o  out  10 100 108   3 111
    add  10 100 108 114
    pus  10 100 108 114   1
    poi  10 100 108 114
 r  out  10 100 108
 l  out  10 100
    dup  10 100 100
 d  out  10 100
    pus  10 100   1
    poi  10 100
    pus  10 100   1
    pus  10 100   1   1
    add  10 100   2
    pus  10 100   2   1
    pus  10 100   2   1   1
    poi  10 100   2   1
    add  10 100   3
    pus  10 100   3   1
    poi  10 100   3
    div  10  33
 !  out  10
 \n out

Copyright © Thomas Schoch 2006 www.retas.de
Image License: Creative Commons Attribution-ShareAlike 2.5