while begins repeating a provided set of rules (like ask) indefinitely as long as a given reporter reports true. If the reporter reports false , while stops repeating the provided rules. For example, if we wanted to create a model of a real-estate market where each buyer continued searching for a house until they found one cheap enough, we would write the following code:

ask turtles [
    let found-home? false
    while [not found-home?] [
        move-to one-of patches with [residents = 0]
        if [price] of patch-here < my-budget [
            set found-home? true
        ]
    ]
]

In the model example below, we have many turtles placed in a grid layout. Each turtle is either purple or green and each is either happy or sad depending on the number of turtles around them. If a turtle has more than 2 neighbors with a different color, we use the while primitive to make each turtle move around the grid until they find a spot that makes them happy.