Generative Poetry with L-Systems

by Adam Parrish

This program uses an L-System to re-order the words of a source text. The resulting text retains some of the semantics of the original text, but with a significantly modified structure whose rhythm is both similar and foreign to the ordinary rhythm of language.

Methodology

Graphical L-Systems commonly make use of a "turtle" metaphor, wherein each token in the expanded L-System string corresponds to a graphical operation (draw a line, move forward without drawing, rotate current heading, etc.). This program uses the same metaphor, except the "turtle" is limited to moving over a one-dimensional array of words. The only "draw" operations are printing the word at the current array index and advancing to the next line.

Recognized rule tokens:

• P prints the current word
• N prints a new line
• + moves to the next word in the source text, and - moves to the previous word. Both + and - can be preceded by a single digit (0-9): 5+ is the same as +++++.
• [ saves the current position on the stack, and ] pops it.

Note: Decrementing/incrementing beyond the bounds of the array will cause the index to wrap, e.g., for a text with 100 words, an index of -6 is the same as 94, and an index of 109 is the same as 9.

Try It Out

Use the form below to try out the program yourself. Perl source code available here.