Typed Intro

Many of the most common languages in use today require you to specify the types on inputs and outputs of a function. That is to say, they every function requires a signature.

There are two main benefits to this kind of typing:

1. Speed. The code runs faster when the computer has no doubt that a certain variable always contains a certain kind of value, like a posn.

2. Reliability. The computer can check before starting the program that there is never a time when the posn-x function is called on a color. In regular Racket, this kind of mistake causes the program to halt with an error when the mistake runs. In Typed Racket, the mistake is detected before the program starts running - there is no suspense and no uncertainty.

Initial Setup

1. One time per computer:

   File -> “Install Package…” -> Enter “picturing-programs-typed” and choose the “Install” button.

2. Beginning of every file:

    #lang typed/racket
    (require typed/picturing-programs)
   

3. End of the file - you need to run the check-expects manually.

    (test)