Functional Programming

• Functions are first-class citizens: create, bind to variables, pass to functions and return as values
• Allows declarative and composable style: emphasis on modularity, no side effects, formally verifiable, fewer bugs

Elements of Programming

The language also serves as a framework within which we organize our ideas about processes. Thus, when we describe a language, we should pay particular attention to the means that the language provides for combining simple ideas to form more complex ideas. Every powerful language has three mechanisms for accomplishing this: Primitive Expressions, Means of Combination, Means of Abstraction.

Primitive Expressions

1. Numbers: 3 21412 1.3e-10
2. Strings: “hello, world”
3. Boolean (true or false): #t #f #nil
4. Primitive Procedures (Built-in to the Interpreter)

Some Primitive Procedures

• Arithmetic + - * / modulo remainder sqrt
• Boolean > ≥ < ≤ = and or not equal? eq?
• Strings string-length string?
• Mathematical abs even? expt positive? negative?
• Lists cons quote list list-ref car cdr

How to use primitive procedures?

Expressions representing numbers may be combined with an expression representing a primitive procedure (such as addition or multiplication) to form a compound expression that represents the application of the procedure to those numbers.

General form: (op arg1 arg2)

(+ 13 14)
(* 5 99)
(+ 2.7 100.001)