WolframLang: Expression

WolframLang source code is made of expressions. Every part in source code, is expression. (there is no such thing as “statements”.)

What this means is that, any valid syntactic unit returns a value.

Atom

An atom is a indivisible expression, such as number, symbol, string.

[see Atomic Expression]

Expression

Expression is either a single Atom , or a sequence of atoms in the form

a[b, c, etc]

Any of the a, b, c, is again an expression.

this syntax is called FullForm

Head of expression

The a in a[etc] is called the Head of expression.

[see Head of Expression]

List

A list is a expression whose head is List.

[see List]

• The form a[etc] is called FullForm.
• Any Atomic Expression is in FullForm by itself.
• The WolframEngine convert shortcut syntax to FullForm internally before eval.
• All Pattern Matching are done against FullForm.