WolframLang: CompoundExpression and Semicolon

By Xah Lee. Date: . Last updated: .

One single semicolon in WolframLang, e.g.


is a short syntax for

CompoundExpression[a, b]

It is used to group several expressions together as one syntactic unit. It is similar to many language's code block by braces {}, or lisp's progn.

Short syntaxFullForm
expr1;expr2CompoundExpression[expr1, expr2]
expr1;CompoundExpression[expr1, Null]
CompoundExpression[expr1, expr2]

🔸 SHORT SYNTAX: expr1;expr2

Eval all arguments and return the value of last argument.


Examples of CompoundExpression

CompoundExpression is frequently used in If, Function, Module, or anytime when you need to do several computation as a single expression as one arg to function.


If[x, doTrueExpr1; doTrueExpr2; etc, doFalseExpr1; doFalseExpr2; etc ]

[see WolframLang: If Then Else (Conditional)]

Function[{vars}, expr1; expr2; etc]

[see WolframLang: Define Function]

Module[{vars}, expr1; expr2; etc ]

[see WolframLang: Local Variable]

Often, you'll find it convenient to put a semicolon at end of some expression. In particular, after assignment. It has the effect of suppressing output. For example, x=3 return 3, but x=3; return Null, and Null output is not automatically printed.

Expression, Atom, Head