diff --git a/README.md b/README.md index 13e9ece..af277b7 100644 --- a/README.md +++ b/README.md @@ -32,32 +32,37 @@ state 0: state 1: - Looks for a 1 to replace by a three -- if symbol = 1, write 3, move to the right, change to state 2. -- otherwise: move to the right, keep state. +- if symbol = 1, write 3, move right, change to state 2. +- otherwise: move right, keep state. state 2: - it looks for a 2 to replace by a 4. - if symbol = 2, write 4, change to state 3. -- else: move to the right, keep state +- else: move right, keep state state 3: - if it doesn't find a 0, go to the left, keep state -- if it finds a 0, write 0, move to the right, go to state 1. +- if it finds a 0, write 0, move right, go to state 1. // As I write this, I realize that if I replace state 0 by state 3, nothing happens. -// Excursus: After competing this project, I searched for similar ones, and found one by a William Bernoudy. My finding the nth prime TM had 14 states and 12 symbols, while his had 14 states and only 10 symbols. But if I replace state 0 by state 3, I have one state less! Anyways, from now on no state is state 3. +// Excursus: After competing this project, I searched for similar ones, and found one by a William Bernoudy. My finding the nth prime TM had 14 states and 12 symbols, while his had 14 states and only 10 symbols. But if I replace state 0 by state 3, I have one state less! Anyways, from now on no state is state 3. We modify state 2, which refers to it. state 0: -- If symbol = 0, go to state 1. -- Else: move to the right, keep state. +- If symbol = 0, move right, change to state 1. +- else: move left, keep state. + +state 2: +- it looks for a 2 to replace by a 4. +- if symbol = 2, write 4, change to state 0. +- else: move right, keep state Now, once all the 1s are turned into 3s, state 1 would go on searching, so we want to modify it to notice that it has run out of threes. state 1: -- if symbol = 1, write 3, move to the right, change to state 2. -- if symbol = 8, write 8, move to the right, change to state 4. -- otherwise: move to the right. +- if symbol = 1, write 3, move right, change to state 2. +- if symbol = 8, write 8, move right, change to state 4. +- otherwise: move right. If there were no 2s left to turn to 4s, then n|m (n divides m). But if there are, n can still divide m, so we keep on going. @@ -68,7 +73,7 @@ state 4: We also notice that if state 2 finds no 2s to turn into 4s, then ¬ (n|m), so we add that option. state 2: -- if symbol = 2, write 4, change to state 3. +- if symbol = 2, write 4, change to state 0. - if symbol = 9, ACCEPT. - else: move to the right. @@ -88,8 +93,7 @@ End. (divisor 1.1) Accepts if n|m or if n=m. Now the input is: 05111...11822..229 -The 5 will be to a 6 once we change the 2 that corresponds to the 8. If there is no such 2, n = m. -So we modify state 4 and 5 and create a state 6. +The 5 will be cahnged to a 6 once we change the 2 that corresponds to the 8. If there is no such 2, n = m. So we modify state 4 and 5 and create a state 6. state 5: - if it reads a 3, write 1, move left, keep state. @@ -103,6 +107,94 @@ state 4: state 6: - if it reads a 5, accept. -- if it erads a 6, reject. +- if it reads a 6, reject. +- else: move to the left. + +End. + +(is prime 1.1) Accepts if n is prime. + +We start with: 0518777...77722..229 + +This reads: The initial n=2, after which there are enough 7s to increase n to find divisors of m. + +Q: But, how many 7s? + +A: Well, a priori at least sqrt(n), but up to n, if you one. + +Q: But Nuño, if you put ceil(sqrt(n)) '7's, aren't you offloading some of the calculations to yourself instead of making the machine calculate it? + +A: Yes, I am. + +Anyways, right now the only state which can accept is state 2, which does so if ¬(n|m) for a given n. Instead of accepting, we want to increase n by 1. We modify state 2, and create 2 new states: state 7 and state 8. + +state 2: +- if it reads a 2: write 4, move left, change to state 0. +- if it reads a 9: write 9, move left, change to state 7. +- else: move to the right + +state 7: +- if it reads a 6: write 5, move left, keep state. +- if it reads a 4: write 2, move left, keep state. +- if it reads a 3: write 1, move left, keep state. +- if it reads a 0: write 0, move right, change to state 8. + +state 8: +-if it reads an 8: write 1, move right, keep state. +-if it reads a 7: write 8, move right, change to state 3. +- if it reads a 2: ACCEPT. There is no space left, at least one of each pair of divisors has been tried + +End. + +(Find the nth prime 1.1) + +Initial input: 0AA...AA51829␣␣␣...␣␣ + +It will replace an A by a B each time it finds a prime, so if n-1 is the number of 'A's, it will find the nth prime. + +State 9 will change an A to a B. States 10, 11 and 12 initialize n to 2. 12, 13 and 14 move m one step to the right and increase it to m+1. By moving it one step to the right, n is bounded only by m+1. + +The states that can accept are state 6 and state 8, and only state 6 can reject. + +state 6 +- if it reads a 5, write 5, change to state 9. +- if it reads a 6: write 6, change to state 10. - else: move to the left. +state 8: +-if it reads an 8: write 1, move right, keep state. +-if it reads a 7: write 8, move right, change to state 3. +-if it reads a 2: write 2, move left, change to state 9. + +state 9: +- if it reads an A: write B, move right, change to state 10. +- if it reads a 0: ACCEPT. There are no more As to change. +- else: move left. + +state 10: +- if is reads a 1: write 1, move right, change to state 11. +- if is reads a 3: write 1, move right, change to state 11. +- else: move right. + +state 11: +- if it reads a 1: write 8, move right, change to state 12 +- if it reads a 3: write 8, move right, change to state 12 +- if it reads a X: write 8, move right, change to state 12 +- else: REJECT // Shouldn't be seeing anything else. + +state 12: +- if it reads a 1: write 7, move right, keep state +- if it reads a 3: write 7, move right, keep state +- if it reads a 8: write 7, move right, keep state +- if it reads a 2: write 7, move right, change to state 13. +- if it reads a 4: write 7, move right, change to state 13. +- else: move right. + +state 13: +- if it reads a 9: write 2, move right, keep state +- if it reads a 4: write 2, move right, keep state +- if it reads a ␣: write 2, move right, change to state 14 +- else: move right. + +state 14: +- if it reads a ␣: write W, move left, change to state 0.