And They Were Thinking? Basic, Logo, Personality and Pedagogy - History of Computing: Learning from the Past - page 118

many years and passionately believes in the idea of 'learning by doing,' something he
later extended to what might be termed 'learning by making things .'
Given this emphasis, it is difficult to understand the reliance on recursion at the
expense of a general iterative statement. Not once in all my reading have I come
across an assertion that students can be expected to discover a recursive solution to a
problem on their own. All I can find are examples provided to students to explain,
understand, and adapt. In his seminal topic, Mindstorms , [15 p71] Papert states that
“recursion stands out as the one idea that is particularly able to evoke an excited re-
sponse.” That might be so, but he devotes less than two pages to it, mentioning it once
more in the Appendix in the context of 'circular logic' (p109). Brown and Rubinstein
suggest that with suitable prior experience, students can write their own recursive
routine to traverse a tree, but they give no clue to their success rate. They did find that
“if a student couldn't figure out how to write a function, we could not slowly lead him
down the path to discovery” [19: 43]. Once acquainted with WHILE—DO in Basic or
Pascal, or even the primitive Dartmouth-Basic GOTO, students have no trouble in
writing their own indefinite loops. (Murnane [29, 30]. See also Vitale [31 p272 &
272], and Murnane and Warner [32] for examples of experiments where children
could have, but failed to use, recursion.)
A further reason which can be advanced is Logo's Lisp inheritance, essentially
lambda calculus, whereas Basic was deliberately designed to be “as close to ordinary
English combined with elementary algebra as possible” [23 p4]. Logo statements do
not always accord with English, although in its earlier versions it approached it more
closely than in later ones. Indeed, anyone coming to Logo after 1970 would be hard-
put to recognise the original language. For example, Multiply [1 p215] is defined as:
TO MULTIPLY /X/ AND /Y/
10 IS /Y/ “0”
20 IF YES RETURN “0”
30 RETURN SUM OF /X/ AND MULTIPLY OF /X/ AND (DIFF OF
/Y/ AND 1)
END
Even allowing for the difficulty of conceptualising the recursion, it is not English, and
in its early iterations, Logo struggled to make progress. The cure for many of these
problems was provided by Seymour Papert.
Logo is often associated specifically with Papert, and particularly with his Turtle
Graphics. He joined the project in January 1969 as a consultant [1 p1, 33] and his
invention of the Turtle and its commands transformed the language.
A Turtle is a small robot which, when connected to a computer, can move and turn
on the floor. At a stroke this eliminated the gap between entering a program and ob-
serving its outcome, since the Turtle could execute a command as soon as it was en-
tered. It also solved the problem of the student understanding what the command did:
they could walk around behind the Turtle following its movements with their own.
While they might need to be taught the meaning of “TEST IS COUNT /SENTENCE/
1 [18 p45] they could easily appreciate what FORWARD 100 meant because it ac-
corded to their own body actions and their natural language. Turtle Geometry pro-
vides an immediate and meaningful environment for the beginner, relating body
movement to the effect of a Logo statement. Papert [28 p24] describes this as the