with is a reporter primitive that allows us to extract a sub-agentset from an agentset based on a provided set of conditional statements. A condition within a with statement is similar to an if statement. For example, if we wanted to model a predator-prey ecosystem where a hawk could only see brighter colored mice, but not the darker colored ones, we would write the following code:

ask hawks [
    if any? (mice-here with [color = gray and distance myself < 2]) [
        hunt
    ]
]

Notice that we first wrote the name of the agentset (mice-here), then used the with primitive, and then provided our conditional statements within brackets ([ ]).

Things to keep in mind when using with:

• We can use with for all kinds of agent types (turtles, patches, and links).
• You can also do some simple operations within a reporter that comes before with such as customers with [(checking-account + savings-account) > 1000] to get an agentset that contains only the customers whose total account balance is larger than 1000 or circles with [size / 2 > 1] to get an agentset that contains only the circles with a radius larger than 1.

In the model example below, we have three parallel roads and each road has a car on it. In the go procedure, we use with to differentiate between the speeds of blue cars and red cars. Blue cars go twice as fast as red cars when they have enough gas. When a car does not have enough gas, it goes much much slower. Lastly, we use with to stop the model when all the cars run out of gas.