prevprime, nextprime

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Hello,

The following two subroutines are availble in Maple, and I thought it'd
be useful to include them in Octave, too. I'm a new to Octave, so they
may be written more succintly

function m = prevprime(n)
  tmp = n-1;
  stmp = n-1000;
  if isprime(n-1)
    m = tmp;
    return
  endif

  while(i>stmp)
    if isprime(i)
      m = i;
      return
    endif
  endwhile
endfunction

function m = nextprime(n)
  tmp = n+1;
  ltmp = tmp + 1000;
  if isprime(tmp)
    m = tmp;
    return
  endif

  for i=tmp:ltmp
    if isprime(i)
      m=i;
      return
    endif
  endfor
endfunction

Kind regards,
Mads Jensen
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