Lua, 876 bytes
function I(a)a.s=a.s:gsub("(%d)(9*)$",function(n,k)return tostring(tonumber(n)+1)..("0"):rep(#k)end)end function D(a)a.s=a.s:gsub("(%d)(0*)$",function(n,k)return tostring(tonumber(n)-1)..("9"):rep(#k)end):gsub("^0+(%d)","%1")end function m(a,b)local A=K(a)local B=K(b)while V(0,B)do D(A)D(B)end return A end function M(a,b)local A=K(a)local B=K(b)while V(m(B,1),A)do A=m(A,B)end return A end function l(n)return#n.s end function p(a)local A=K(a)local i=K(2)while V(i,A)do if V(M(A,i),1)then return false end I(i)end return true end function V(b,a)A=K(a)B=K(b)if l(A)>l(B)then return true end if l(B)>l(A)then return false end for i=1,l(A)do c=A.s:sub(i,i)j=B.s:sub(i,i)if c>j then return true elseif c<j then return false end end return false end function K(n)if(type(n)=='table')then return{s=n.s}end return{s=tostring(n)}end P=K(io.read("*n"))repeat I(P)until p(P)print(P.s)
Lua, diferentemente de outros idiomas, possui um Tamanho Máximo Inteiro. Quando um número fica maior que 2 32 , as coisas param de funcionar corretamente e Lua começa a tentar fazer estimativas em vez de valores exatos.
Como tal, eu tive que implementar um novo método de armazenamento de números, em particular, eu os armazenei como seqüências de caracteres Base10, porque Lua não tem um limite de tamanho em Strings, além do tamanho da memória.
Eu sinto que essa resposta é muito mais importante para o espírito da pergunta, pois ela mesma deve implementar números inteiros de precisão arbitrários, além de um teste primo.
Explicado
-- String Math
_num = {}
_num.__index = _num
-- Increase a by one.
-- This works by grabbing ([0-9])999...$ from the string.
-- Then, increases the first digit in that match, and changes all the nines to zero.
-- "13", only the "3" is matched, and it increases to 1.
-- "19", firstly the 1 is turned to a 2, and then the 9 is changed to a 0.
-- "9" however, the 9 is the last digit matched, so it changes to "10"
function _num.inc(a)
a.str = a.str:gsub("(%d)(9*)$",function(num,nines)
return tostring(tonumber(num)+1)..("0"):rep(#nines)
end)
end
-- Decrease a by one
-- Much like inc, however, uses ([0-9])0...$ instead.
-- Decrements ([0-9]) by one and sets 0... to 9...
-- "13" only the "3" is matched, and it decreases by one.
-- "10", the "1" is matched by the ([0-9]), and the 0 is matched by the 0..., which gives 09, which is clipped to 9.
function _num.dec(a)
a.str = a.str:gsub("(%d)(0*)$",function(num,zeros)
return tostring(tonumber(num)-1)..("9"):rep(#zeros)
end) :gsub("^0+(%d)","%1")
end
-- Adds a and b
-- Makes A and B, so that the original values aren't modified.
-- B is then decremented until it hits 0, and A is incremented.
-- A is then returned.
function _num.__add(a,b)
local A = str_num(a)
local B = str_num(b)
while B > 0 do
A:inc()
B:dec()
end
return A
end
-- Subs b from a
-- Works just like Addition, yet Dec's A instead of Incs.
function _num.__sub(a,b)
local A = str_num(a)
local B = str_num(b)
while B > 0 do
A:dec()
B:dec()
end
return A
end
-- A % B
-- Makes A and B from a and b
-- Constantly subtracts B from A until A is less than B
function _num.__mod(a,b)
local A = str_num(a)
local B = str_num(b)
while A >= B do
A = A - B
end
return A
end
-- #a
-- Useful for golfiness
function _num.__len(n)
return #n.str
end
-- Primacy Testing
-- Generates A from a and i from 2.
-- Whilst i is less than A, i is incremented by one, and if A % i == 0, then it's not a prime, and we return false.
-- Once that finishes, we return true.
function _num.isprime(a)
local A = str_num(a)
local i = str_num(2)
while i < A do
if A%i < 1 then
return false
end
i:inc()
end
return true
end
-- b < a
-- A and B are generated from a and b
-- Fristly, if the length of A and B aren't equal, then that result is output.
-- Otherwise, each character is searched from left to right, the moment they are unequal, the difference is output.
-- If all the characters match, then it's equal. Return false.
function _num.__lt(b,a)
A=str_num(a)
B=str_num(b)
if #A > #B then
return true
end
if #B > #A then
return false
end
for i=1, #A.str do
As = A.str:sub(i,i)
Bs = B.str:sub(i,i)
if As > Bs then
return true
elseif As < Bs then
return false
end
end
return false
end
-- b <= a
-- Same as b < a, but returns true on equality.
function _num.__le(b,a)
A=str_num(a)
B=str_num(b)
if #A > #B then
return true
end
if #B > #A then
return false
end
for i=1, #A.str do
As = A.str:sub(i,i)
Bs = B.str:sub(i,i)
if As > Bs then
return true
elseif As < Bs then
return false
end
end
return true
end
-- Just straight up returns it's string component. Endlessly faster than the int equivalent, mostly because it never is anything _but_ the string form.
function _num.__tostring(a)
return a.str
end
-- Just set up the metatable...
function str_num(n)
if(type(n)=='table')then
return setmetatable({str = n.str}, _num)
end
return setmetatable({str = tostring(n)}, _num)
end
-- Generate a new str_num from STDIN
Prime = str_num(io.read("*n"))
-- This is handy, because it will call Prime:inc() atleast once, and stop at the next prime number it finds.
-- Basically, if it weren't for all that overhead of making the math possible, that's all this would be.
repeat
Prime:inc()
until Prime:isprime()
print(Prime)
Embora o acima mencionado use Metatables, em vez de apenas funções regulares, como a resposta real, que resultou menor.