First program

A small program can have one value, one function, and one final expression.

let total := 42;
total;

Read it from top to bottom. First Musi learns the name. Then it learns the function. Then the final line uses the names above it.

A function is still a value with a name. The parameter list says what the function needs. The result type says what it gives back.

This is close to a kitchen order. First the ticket says the table. Then a rule says how to add tax or a fee. Then the last line asks for the final amount.

Read the program

let base := 40;
let total := base + 2;
total;  -- 42

Line one binds base. Line two reads base, adds 2, and binds total. Line three evaluates total.

The program does not need a main function for a small first file. A file can be a sequence of expressions while you learn.

Add one rule

Add a comparison when the value needs a check.

let total := 42;
let expected := total = 42;
expected;  -- .True

= compares. It does not bind. The result is a Boolean.