==== Type Judgments for the Type Checking Lab ====

Here are the type judgments we went over in class translated into English form instead of the notation we used in class:

* numeric literal: always results in a number

* boolean literal (true / false): always results in a boolean

* addition / subtraction: if both are numbers, results in a number

* iszero: if input is a number, result is a boolean

* id: look it up in the type environment to find out its type 

* with: results in the type resulting from the body after adding to the type environment that the type of the identifier is the type of the initialization expression

* if: if the type of the conditional is boolean and the types of the two possible branches are the same, results in the type of either branch

* lambda: results in a function from the declared type of the input parameter to the return type of the body after adding to the type environment that the formal parameter is the declared type

* app: if the operator is a function (t1 -> t2), and if the type of the actual parameter is type t1, results in type t2.