WolframLang: CompoundExpression and Semicolon

By Xah Lee. Date: . Last updated: .

Semicolon in WolframLang, e.g. a;b 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, etc]
(short syntax: expr1;expr2;etc)
Eval all arguments and return the value of last argument. CompoundExpression

CompoundExpression (or the semicolon) 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.

Examples:

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

[see WolframLang: If Then Else (Conditionals, Branching)]

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 printed.

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