skip the loop if current is 0

src/lib.rs

@@ -131,6 +131,28 @@ pub fn eval_mem<'a>(bf_str: &&str, mem: &'a mut [u8], pointer: &mut usize) -> Re
             continue
         }
         if char == '[' {
+
+            // if current is 0
+            if mem[*pointer] == 0 {
+                // skip the loop completely
+                let mut p = pos.clone();
+                loop {
+                    if p == progsize {
+                        return Err(
+                            BrainFuckError::new(format!("Unmatched '[' ({})", pos), mem)
+                        );
+                    }
+
+                    if chars[p] == ']' {
+                        pos = p + 1;
+                        break;
+                    }
+
+                    p += 1;
+                }
+                continue
+            }
+
             loop_stack.push(pos);
             continue
         }