It's a plugin.
You can create a fullName as a function on the prototype like
fullName: fn(){
return this.attr('first')+this.attr('last')
}
If fullName called in a template, it will automatically be live bound
{{person.fullName}}
If you want fullName as a compute that you can pass around:
fN = can.compute(person.fullName, person)
fN() //-> "Justin Meyer"
You might be able to do that like
person.compute("fullName")
Sent from my iPhone
Sent from my iPhone