OOP Dot Notation, Dot Before Data or After?

By Xah Lee. Date: . Last updated: .

In the dot notation of object oriented programing language design, there's a dilemma, a inconsistency, of whether data comes before dot, or after the dot.

The OOP Dot Notation

The syntax of object oriented programing language is commonly like this:


Where object is the meat you want to work on, and the part in round bracket option is secondary.

Python Case

For example, in Python you have:


[see Python: String Methods]

However, sometimes there's categorical pigeon hole problem, and the OOP language designers have a dilemma: should data be the object or class the object? This particularly happens for {string, regex, math, number} things.

For example, in Python regex, you have:

re.sub(regex, replacement, string)

where the meat is the last parameter string, and the prefix the “re”, is the regex class object. [see Python: regex Example]

JavaScript Case

This happens in JavaScript too. Here's some normal examples, where the meat is the first thing:


string.replace(regex, replacement)

[see JavaScript String Methods]

now witness this:


[see JavaScript Regex Object Methods]

Above, the meat is the string, while the regex is the object (a regex string).

And, now, LOOK:

Math.max.apply(context, list)

Above, the meat is the list. The “Math” is a global object, and “max” is one of its method, and “apply” is a method inherited from a Function object.

OOP Dot Notation = Complexity Multiplied by Confoundedness

Given x.y(z), there is no way to tell, syntactically, which part is the data. Especially so in most languages today, such as {JavaScript, Python, Ruby} , where everything is a object, including function and data, and you can set it to any variable. The bottom line reached complexity multiplied by confoundedness.

solution? ban the fsck of it. Instead, everything should be a function:


The meat is always in the function's parameter spec, while the namespace.function_name uniquely identify its {module, namespace, purpose}. e.g. {math.sin(3), string.trim(" xyz "), regex.match("x123", "/d+"), ….}.

[google plus discussion https://plus.google.com/+XahLee/posts/Wbjqeqw5HCq]

postscript: we should note that the dot notation isn't the only possible notation for object oriented language. The functional notation as in f(x,y,z) (meaning className(methodName, data1, data2) ) could also work. [see Object Oriented Programing (OOP) Jargons and Complexities]

But Dot Notation is Easier to Read?

for example, x.a(…).b(…).c(…) is more readable than c(b(a(x)))

It is postfix notation that helps reading.

Dot notation of OOP, is 2 things. (1) a postfix notation. (2) requires a relation between 2 operands, usually, the left side is a class or object, and the right side is its method/property.

You do not need OOP dot notation to have post-fix notation.

Here is some example of postfix or prefix notation.

See also: JS: Pipe Function Instead of Method Chaining

All of the above, has sequential forms that are not nested.

In the functional prefix or postfix notation, the syntax and semantics has a simple correspondence.

The issue with OOP's dot notation, is the irregular correspondence between syntax and semantics.

In the OOP's dot notation, given a.b.c(d), sometimes “a” is the data, sometimes “d” is the data. It is impossible to know syntactically.

[see Concepts and Confusions of Prefix, Infix, Postfix and Lisp Notations]

Unix Pipe, Dot Notation, Postfix Notation