/*
Print the first 100 prime numbers.
The program is structured for clarity:
- A helper function determines whether a number is prime.
- A generator function collects primes until reaching the desired count.
- Comments explain the reasoning behind each step.
*/
fn is_prime(n: u32) -> bool {
/*
Return true if n is a prime number.
The function uses a straightforward and efficient approach:
- Reject numbers below 2.
- Only test divisors up to the square root of n.
Using i * i <= n avoids repeated floating‑point work.
*/
if n < 2 {
return false;
}
let mut i: u32 = 2;
while i * i <= n {
if n % i == 0 {
return false; // Found a divisor → not prime
}
i += 1;
}
true // No divisors found → prime
}
fn first_n_primes(count: usize) -> Vec<u32> {
/*
Generate a vector containing the first `count` prime numbers.
The function increments through natural numbers,
checks primality, and collects primes until the vector is full.
*/
let mut primes: Vec<u32> = Vec::with_capacity(count);
let mut number: u32 = 2; // Start from the first prime candidate
while primes.len() < count {
if is_prime(number) {
primes.push(number);
}
number += 1;
}
primes
}
fn main() {
/*
Compute and print the first 100 prime numbers.
Each prime is printed on its own line.
*/
let primes: Vec<u32> = first_n_primes(100);
for p in primes {
println!("{}", p);
}
}
/*
run:
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97
101
103
107
109
113
127
131
137
139
149
151
157
163
167
173
179
181
191
193
197
199
211
223
227
229
233
239
241
251
257
263
269
271
277
281
283
293
307
311
313
317
331
337
347
349
353
359
367
373
379
383
389
397
401
409
419
421
431
433
439
443
449
457
461
463
467
479
487
491
499
503
509
521
523
541
*/
