Port and Stash

And this was the thing Port could not do alone, the thing Port had learned the hard, fluttery way: Port could let information in, but Port could not keep it. A number came flying through the doorway — a good number, a needed number — and Port passed it along and reached for the next thing; and if there had been nowhere to put that number, it would simply have slipped away. Gone. Out the other side, unrecoverable. Port's hands were always full of the next thing arriving; Port had no way to hold the last thing at all. "That's the part that used to scare me," Port admitted. "All this coming in, and me unable to hold a single bit of it. Like catching rain in open hands. I can open the door. I just can't keep what walks through it." It is the commonest beginner bug there is: read an input, never store it, and wonder why the program forgot the answer the instant it got it.

But Stash could keep it. Keeping was Stash's entire calm nature. Stash was a variable — a plain labeled box — and the whole point of Stash was to hold a value until it was called for. When Port passed something through, Stash took it, tucked it safely inside, and wrote a name on the front so it could be found again: score, name, count. Whatever it was, Stash held it, steady and unbothered, for as long as the program needed — a second, an hour, the whole run. "You bring it in, I hold it," said Stash, catching the number Port tossed and setting it gently inside. "That's the deal. You're the door; I'm the box — the state. Ask me for it whenever; I'll have it right here, exactly where you left it, name still on the front." And later, when the program did ask — what was that number again? — Stash opened up, and there it was, safe and sound, ready to use.

So they worked the doorway together all day, the pair of them, in a rhythm as easy as breathing. Something came through the door — Port caught it. Port turned and passed it over — Stash held it. The program called for it — Stash opened up and handed it back — Port sent the answer out into the world. In through Port, held by Stash, out through Port again. Read, store, use, respond. Over and over, the whole warm humming day. "Funny how it works," said Port, in a quiet moment between visitors. "On my own I'm just a door with the wind blowing through — everything comes in and everything leaves and I keep none of it." "And on my own," said Stash, "I'm just an empty box with a name on the front and nothing to hold. I can keep anything — but only if somebody brings it to me first." Neither role is the program; both together are how a program remembers what it was told.