use vstd::prelude::*;
fn main() {}
verus!{


fn f1_linear_search(nums: Vec<i32>, target: i32) -> (ret: i32)
requires
    nums@.len() < 0x8000_0000,
{
    let mut i = 0;
    while i < nums.len()
    {
        if nums[i] == target {
            break;
        }
        i = i + 1;
    }
    if i == nums.len() {
        -1
    } else {
        i as i32
    }
}


spec fn step1(__hp0: Seq<i32>, __hp1: i32, outp: i32) -> bool {
    (outp < __hp0.len())
    && (outp >=0 ==> __hp0[outp as int] == __hp1)
    && (outp >=0 ==> forall |i: int| 0 <= i < outp as int ==> #[trigger]__hp0[i]!= __hp1)
    && (outp < 0 ==> forall |i: int| 0 <= i < __hp0.len() as int ==> #[trigger]__hp0[i] != __hp1)
}

fn chain_driver(nums: Vec<i32>, target: i32) -> (r_final: i32)
    requires
        nums@.len() < 0x8000_0000,
    ensures
        step1(nums@, target, r_final),
{
    let x1 = f1_linear_search(nums, target);
    proof {
        assert(step1(nums@, target, x1));
    }
    x1
}

} // verus!