IN WHICH OUR PROTAGONIST LEARNS THE IMPORTANCE OF THE BASE CASE
I was three years old. By this point in my life, the residents of Sesame Street had educated me about as well as any community of puppets could reasonably be expected to educate any small child. Family legend has my father holding me, age fifteen months, as he selected an ice cream treat from the Dickie Dee vendor outside our Virginia home. I don’t know if I recognized the varieties of snacks, but apparently I could make some sense of their names. “I,” I enunciated, pointing. “C. E. C…”
Incredulous, my father informed my mother, “She knows letters.” Since neither of them had thought to teach me the alphabet by that point, Cookie Monster and his friends were quickly credited with this development. I soon learned the rest of the alphabet with the aid of refrigerator magnets and blocks. A few months later, I was reading.
With the alphabet under my belt, I turned my attention to the Count’s endless enumeration of everything under the sun, and within less than a year I could rattle off the integers from one to two hundred in sequence. Two hundred exactly, by the way, and no further. Why I knew that one hundred and one came right after one hundred but was unable to extrapolate any further I have no idea, but my parents had good reason for not furnishing that connection: so proud was I of my ability to count to two hundred that I would count to two hundred on the telephone, to my grandparents, every single time they called. Long distance. And this was back in the olden days when long distance cost an arm and a leg, so when it became clear that I was not to tire of my long distance counts to two hundred, my mother gently pointed out that maybe my grandparents didn’t want to hear me count to two hundred over the phone anymore. I threw a fit; didn’t they love me? By the way, Mom and Dad, I stand by that tantrum, because what the hell is the point of grandparents if not to have someone to listen to – and enjoy listening to – some two-and-a-half-year-old kid count to two hundred over the phone, even if it’s costing them fifty cents a minute to hear it?
Anyway, my point here is, by the time I was three I already knew how to read and how to count, so I guess I was old enough to learn computer science – specifically, recursion – and fortunately, Big Bird was on hand to teach me.
Big Bird was painting a bench. He’d just finished applying the last coat of paint, and his friends were admiring his handiwork. As he replaced the paint brush, he explained – concerned citizen that he was – that it was necessary to warn any passers-by that this was a freshly-painted bench. This made sense to me, because I remembered a previous episode in which whatshisface, the mime, sat down on a freshly-painted bench and got white stripes all over his black suit. Big Bird would have none of that, so he produced a blank piece of paper and wrote WET PAINT on it, and hung it by the bench. His only writing implements, however, were the paint and paintbrush he’d brought with him, so after creating the WET PAINT sign he realized that the sign itself contained wet paint, and so he needed to create another WET PAINT sign, to warn people about the first sign. So he created the second sign, and – apparently having learned nothing from his experience with the first sign – realized that he’d need a new one.
I watched this intently, and suddenly it dawned on me: every WET PAINT sign demanded another. I got it, but Big Bird didn’t. I got worried; would he be doing this forever? Or would someone give him a crayon and tell him to use it for the next sign?
Soon the scene ended, and I distractedly watched for the next few minutes as the mime explained the WALK/DON’T WALK signs, and as the Count showed that it doesn’t matter how you arrange the blocks because you still have the same number of them, and as someone didn’t want to share his cookie with Cookie Monster until Kermit came by to teach a lesson about sharing. Whatever. I didn’t care, because I was concerned that Big Bird was still making WET PAINT signs.
Cut to the next scene: Big Bird surrounded by hundreds – maybe even two hundred – WET PAINT signs, happily making another one because the last one was still wet. And no one handed him a damned crayon, and the episode ended right there.
I burst into tears.
My mother, startled (her toddler was bawling at the end of Sesame Street, after all), hurried into the family room and asked me what was wrong, and I blubbered something about the endless production of WET PAINT signs and how Big Bird would be making them forever because each sign told him to make another one. FOREVER. I couldn’t think of anything worse than spending one’s entire life making WET PAINT signs, and I worried that that was to be Big Bird’s fate. It troubled me more than I could put into words. That happy yellow bird, doing this for the rest of his life. And he showed such promise! Would he never get to have a family? go to the park again? And what of Snuffleuppagus?
Mom obviously hadn’t been expecting this, but she quickly assured me that no, Big Bird wasn’t going to spend his whole life making WET PAINT signs. As a matter of fact, he stopped soon after that episode of Sesame Street ended. Because, uh, Grover told him he didn’t have to make the signs anymore. In fact, just you wait, honey, tomorrow on Sesame Street Big Bird will be doing something completely different.
Will he really? I sniffled.
Yes, honey, he will. I promise.
How do you know?
Because, said Mom, I know all of the people on Sesame Street and they told me what they were going to be doing tomorrow.
And you know, I may have known how to read and count to two hundred, and I may have known all sorts of shapes – not just the easy ones like circle and square and triangle, but also trapezoid and pentagon and parallellogram – by the time I was three, but let me tell you, I ate that shit right up. Okay, cool. Big Bird wouldn’t be making WET PAINT signs forever. Mom said so herself. I could sleep at night.
The next day, I saw that Mom had been right, because there on TV was Big Bird singing a song about cooperation and there were no WET PAINT signs anywhere in sight. Good old Grover. Mom knew everything, apparently.
It wasn’t until several years later that I learned that the sort of structure displayed by the self-producing WET PAINT signs – a set of instructions that includes the instruction to follow itself – had a name: recursion. During my first year of university, some boring CS prof whose name I forget explained this all in the most monotonous way imaginable, and told us that if we wrote a recursive function then it would call itself until it had a good reason not to, that is, a base case that ensured it would stop, infinite loops are bad, yadda yadda, blah blah.
And all I could think of was a computer that would be making WET PAINT signs forever and ever because there was no IF CRAYON branch to lead into a ALL SIGNS ARE DRY base case.
It still bothered me, a decade and a half later, and I took pains to ensure that all of my recursive functions would terminate in good time.
That was Sesame Street’s contribution to computer science. Its contribution to real analysis, unfortunately, had not been subjected to peer review: I remember the Count arranging ten blocks in a row, in a pyramid, in a square, informing us that no matter how you placed them, they’d add up to the same number.
Sure, Count. With a series that converges absolutely.