Wolfram: Expression

WolframLang source code is made of expressions. (there is no such thing as statements.)

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

Atom

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

• Wolfram: Atomic Expression

Expression

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

• a[]
• a[b]
• a[b, c]
• a[b, c, etc]

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

this syntax is called FullForm.

• Wolfram: FullForm Syntax

Head of expression

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

• Wolfram: Head of Expression

List

A list is a expression whose head is List.

• Wolfram: 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.