#primesmatter ;)

src/main.rs

@@ -6,16 +6,44 @@ fn log_2(x: BigUint) -> u64 {
 }
 
 fn is_prime(number: BigUint) -> bool {
-    let a = log_2(number.clone()+1u8);
-    if BigUint::from(2u8).pow(a as u32)-BigUint::from(1u8) != number {
-        eprintln!("only supports numbers of type (2^x)-1");
-        std::process::exit(1);
+    if BigUint::from(1u8) == number {
+        return false;
+    }
+    if BigUint::from(4u8) > number  {
+        return true;
     }
 
-    let mut last = BigUint::from(4u8)%number.clone();
     let two = BigUint::from(2u8);
+
+    // number = 2^a - 1
+    // a = log2(number + 1)
+    let a = log_2(number.clone()+1u8);
+    if BigUint::from(2u8).pow(a as u32)-BigUint::from(1u8) != number {
+        //eprintln!("only supports numbers of type (2^x)-1");
+        let mut i = BigUint::from(0u8);
+        let one = BigUint::from(1u8);
+        let zero = BigUint::from(0u8);
+        
+        let sqrtnum = number.sqrt()+one.clone();
+        let mut is_prime = true;
+        loop {
+            i = i + one.clone();
+            if i == sqrtnum {
+                break;
+            }
+            if sqrtnum.clone()%i.clone() == zero {
+                is_prime = false;
+                break;
+            }
+        }
+        return is_prime;
+    }
+
+    // 4 12 194
+    let mut last = BigUint::from(4u8);
+    
     for _i in 2..a {
-        last = (last.clone()*last-two.clone())%number.clone();
+        last = (last.pow(2)-two.clone())%number.clone();
     }
     if last == BigUint::from(0u8) {
         true
@@ -32,14 +60,11 @@ fn main() {
     stdin.read_line(&mut buffer).expect("could not read from stdin");
     buffer = buffer.trim().to_owned();
     
-    let number = BigUint::parse_bytes(&buffer.as_bytes(), 10).expect("expected number");
-
-    // number = 2^x - 1
-    // x = log2(number + 1)
+    let number = BigUint::parse_bytes(&buffer.as_bytes(), 10).expect("expected positive number");
 
     if is_prime(number.clone()) {
-        println!("{number} is a prime");
+        println!("\n{number} is a prime");
     } else {
-        println!("{number} is not a prime");
+        println!("\n{number} is not a prime");
     }
 }