What is “Orthogonality”?

Question

What does \"orthogonality\" mean when talking about programming languages?

What are some examples of Orthogonality?

Answer 1

While talking about project decisions on programming languages, orthogonality may be seen as how easy is for you to predict other things about that language for what you've seen in the past.

For instance, in one language you can have:

str.split

for splitting a string and

len(str)

for getting the lenght.

On a language more orthogonal, you would always use str.x or x(str).

When you would clone an object or do anything else, you would know whether to use

clone(obj)

or

obj.clone

That's one of the main points on programming languages being orthogonal. That avoids you to consult the manual or ask someone.

The wikipedia article talks more about orthogonality on complex designs or low level languages. As someone suggested above on a comment, the Sebesta book talks cleanly about orthogonality.

If I would use only one sentence, I would say that a programming language is orthogonal when its unknown parts act as expected based on what you've seen. Or... no surprises.

;)

Answer 2

Orthogonality is the property that means "Changing A does not change B". An example of an orthogonal system would be a radio, where changing the station does not change the volume and vice-versa.

A non-orthogonal system would be like a helicopter where changing the speed can change the direction.

In programming languages this means that when you execute an instruction, nothing but that instruction happens (very important for debugging).

There is also a specific meaning when referring to instruction sets.

Answer 3

From Eric S. Raymond's "Art of UNIX programming"

Orthogonality is one of the most important properties that can help make even complex designs compact. In a purely orthogonal design, operations do not have side effects; each action (whether it's an API call, a macro invocation, or a language operation) changes just one thing without affecting others. There is one and only one way to change each property of whatever system you are controlling.

Answer 4

In programming languages a programming language feature is said to be orthogonal if it is bounded with no restrictions (or exceptions). For example, in Pascal functions can't return structured types. This is a restriction on returning values from a function. Therefore we it is considered as a non-orthogonal feature. ;)

Answer 5

Think of it has being able to change one thing without having an unseen affect on another part.

Answer 6

from wikipedia:

Computer science

Orthogonality is a system design property facilitating feasibility and compactness of complex designs. Orthogonality guarantees that modifying the technical effect produced by a component of a system neither creates nor propagates side effects to other components of the system. The emergent behavior of a system consisting of components should be controlled strictly by formal definitions of its logic and not by side effects resulting from poor integration, i.e. non-orthogonal design of modules and interfaces. Orthogonality reduces testing and development time because it is easier to verify designs that neither cause side effects nor depend on them.

For example, a car has orthogonal components and controls (e.g. accelerating the vehicle does not influence anything else but the components involved exclusively with the acceleration function). On the other hand, a non-orthogonal design might have its steering influence its braking (e.g. electronic stability control), or its speed tweak its suspension.1 Consequently, this usage is seen to be derived from the use of orthogonal in mathematics: One may project a vector onto a subspace by projecting it onto each member of a set of basis vectors separately and adding the projections if and only if the basis vectors are mutually orthogonal.

An instruction set is said to be orthogonal if any instruction can use any register in any addressing mode. This terminology results from considering an instruction as a vector whose components are the instruction fields. One field identifies the registers to be operated upon, and another specifies the addressing mode. An orthogonal instruction set uniquely encodes all combinations of registers and addressing modes.