Write a function used to list primes

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Ruihan Yi 2020-5-16

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评论： Ruihan Yi 2020-5-20

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I'm a beginner in MATLAB.

This task is to wirte a function called 'primeList' to list all primes form 1 to p. isprime is not allowed to be used.

AND the background of this queation is Eratosthenes Sieve so I must use this sieve (mod is not allowed)

I have tried for more than 3 days, now, what I writed can print the primes when p>4.

However, I don't know how to let it print when p =2 or 3?

my code ↓

function primeList=EratosthenesSieve(p)  % creat a list of prime numbers from 2 to p
%p=input('please enter a positive integer p, p>2, p= ') 
%take a positive integer p as input (not essential)
primeList=1:p;
a=2;  %The first prime is 2
while a.^2<=p    %End when reach sqrt(p)
primeList(a^2:a:p)=0   %Make all the numbers which are multiples of a to be 0
primeList(1)=0; %Make 1 to be 0 as 1 is neither prime nor composite
a=find(primeList>a,1); %find the next unmarked number to continue
end
primeList(primeList==0)=[]  %only keep primes as an array
%special conditions:p=2 or 3 ？？？
end