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Great idea for a book. 1) What "level" of programmer will this be pitched at? e.g. No experience programming, regular "working programmer" with no theory backg

by defen 10y ago

Great idea for a book. 1) What "level" of programmer will this be pitched at? e.g. No experience programming, regular "working programmer" with no theory background, someone with an undergrad CS degree, someone with 20 years of industry experience, etc. 2) Have you decided on the Turing machine yet? Will the interpreter be provided as a "given" or will the reader have to write an interpreter in a higher-level language first? e.g. I'm imagining something that reads a state table description and a representation of an input tape, performs the work, and then hopefully stops and outputs the tape.

braythwayt 10y ago
Like JavaScript Allongé, I am planning for it to be readable by someone with just a smattering of programming familiarity. But also like JavaScript Allongé, I hope for a fairly substantial learning slope. I don’t imagine writing the first interpreter will be onerous. Here’s one I wrote specifically to be “pessimum” without being gratuitously so: const aMachine = (() => { const HALT = 'HALT'; const LEFT = 2; const RIGHT = 3; function kiss4({ description, tape: _tape }) { const tape = Array.from(_tape); let tapeIndex = 0; let currentState = description[0][0]; while (true) { if (tapeIndex < 0) { console.log('moved off the left edge of the world'); console.log({ tapeIndex, currentState, currentMark, tape: tape.join(' ') }); return tape; } const currentMark = tape[tapeIndex]; const rule = description.find(([state, mark]) => state === currentState && mark === currentMark); if (rule == null) { if (currentState !== HALT) { console.log('no rule for this state and mark'); console.log({ tapeIndex, currentState, currentMark, tape: tape.join(' ') }); } return tape; } const [_, __, nextState, action] = rule; if (action === LEFT) { --tapeIndex; } else if (action === RIGHT) { ++tapeIndex; if (tape[tapeIndex] == null) tape[tapeIndex] = 0; } else if ([0, 1].includes(action)) { tape[tapeIndex] = action; } currentState = nextState; } } return Object.assign( ({ description, tape = [] }) => kiss4({ description, tape }), { constants: { LEFT, RIGHT, HALT } } ); })();

by defen 10y ago

braythwayt 10y ago

Like JavaScript Allongé, I am planning for it to be readable by someone with just a smattering of programming familiarity. But also like JavaScript Allongé, I hope for a fairly substantial learning slope. I don’t imagine writing the first interpreter will be onerous. Here’s one I wrote specifically to be “pessimum” without being gratuitously so: const aMachine = (() => { const HALT = 'HALT'; const LEFT = 2; const RIGHT = 3; function kiss4({ description, tape: _tape }) { const tape = Array.from(_tape); let tapeIndex = 0; let currentState = description[0][0]; while (true) { if (tapeIndex < 0) { console.log('moved off the left edge of the world'); console.log({ tapeIndex, currentState, currentMark, tape: tape.join(' ') }); return tape; } const currentMark = tape[tapeIndex]; const rule = description.find(([state, mark]) => state === currentState && mark === currentMark); if (rule == null) { if (currentState !== HALT) { console.log('no rule for this state and mark'); console.log({ tapeIndex, currentState, currentMark, tape: tape.join(' ') }); } return tape; } const [_, __, nextState, action] = rule; if (action === LEFT) { --tapeIndex; } else if (action === RIGHT) { ++tapeIndex; if (tape[tapeIndex] == null) tape[tapeIndex] = 0; } else if ([0, 1].includes(action)) { tape[tapeIndex] = action; } currentState = nextState; } } return Object.assign( ({ description, tape = [] }) => kiss4({ description, tape }), { constants: { LEFT, RIGHT, HALT } } ); })();