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The overview of a programming environment
- The elements of programming
- Expressions
- Namespacing and function composition
- Conditionals
- Evaluation model
- Related resources
The study of Computational processes start with the study of a programming environment. The programming environment is mostly a given in programming but let's inspect and state some things (and some are obvious) about it.
The elements of programming
A programming language enables you to make the following:
- Expressions ranging from a primitive value to a complex type.
- A way to combine simple expressions into complex ones.
- A way to abstract procedures into higher-level processes.
Expressions
Expressions may be of a primitive value (e.g., 265, -1.0, 'string) or combinations which are composed of operators and expressions (e.g., (+ 2 6), (* 6 3)).
An expression can also hold expressions referred to as a subexpression (e.g., (+ (* 5 12) (- 54 6) 9)).
[fn:: In Lisp, it uses the prefix notation which places the operator in the leftmost of the expression.
It has the advantage of removing ambiguity for indicating its arguments (e.g., 5 + 67 + (6 * 4) vs (+ 5 67 (* 6 4))).]
Namespacing and function composition
A programming environment should have a way to refer to computational objects.
These often comes in the form of names with each referring to a value (e.g., (define x 10)).
A programming language should also provide the way to combine simple procedures to compound procedures (e.g., (define (square x) (* x x))) which can be referred to by name (e.g., (square 10) evaluates to 100).
With that said, we can then combine compound procedures to create a procedure of higher level (e.g., (define (sum-of-squares x y) (+ (square x) (square y)))).
Conditionals
With expressions, environment, and function composition, we can create simple programs. However, we cannot create functions that may test for the value (e.g., piecewise functions). For this, a way to conditionally evaluate a value is a must for a programming language.
Here's an example function of getting the absolute value of a number.
(define (abs x)
(cond
((< x 0) (- x))
(else x)))