Limitations of the Tree-Walk Interpreter # QLogo was implemented as a tree-walk interpreter. What this means is that the execution happens by traversing the AST nodes and performing the corresponding operations for each node. For example, this code: PRINT 2 + 3 * FN :A Generates this tree: So, using a tree-walk interpreter in this example would generate three nested subroutine calls from the call to PRINT to the call to FN :A. ...
When XKCD Draws Bob Ross Painting Happy Trees With a Turtle # XKCD comic #2601, titled “Instructions”, takes an April Fool’s Day turn from the usual visual format. Instead of a traditional comic, author Randall Munroe provides an audio file containing a lengthy Logo program. This program, when executed, draws a detailed image filled with references to lots of things, but especially to turtles and Bob Ross. From Audio to Code # Dedicated fans took on the challenge of transcribing the audio into a working Logo program. ...
Pixels # UCBLogo was designed to run on DOS machines, which had a well-defined screen resolution. Windows wasn’t really a thing at the time, and so you could count on the turtle’s graphics region being very static. Also, since screen resolutions were so low, a single pixel was much larger, and very visible. So it made sense at the time that everything the turtle did was defined in pixels. ...
Sieve of Eratosthenes # I’m looking for ways to stress-test QLogo. A suggestion that came up in my Google search was the Sieve of Eratosthenes. The algorithm goes like this: erasthotenes(n): Create a list of all integers from 2 to n. Remove all multiples of primes up to the square root of n. The remaining list of numbers are the primes. I don’t consider myself an expert in the Logo language. ...
Moving from Jekyll to Hugo # Over the past few years I have jumped from computer to computer before finally settling in with my current machine (Macbook Air M2). In that time I haven’t kept this website up. With my new computer I have taken the opportunity to restart qlogo.org development using Hugo instead of Jekyll. Removing Support for Objects from QLogo # Recently, I have been implementing support for objects within QLogo. ...