If and Then

The if keyword precedes a condition, must be followed by then and a statement. The statement may optionally be followed by else and another statement. This creates a binary branch.

If then

if condition
    then true_statement
else false_statement;

condition is a Boolean expression that evaluates to true xor false. true_statement is executed if condition evaluates to true. false_statement is executed if condition evaluates to false. A compile-time error occurs if the type of condition does not evaluate to a Boolean value.

Multiple statements in if then branch

If you need two or more statements for true_statement or false_statement, enclose them within a begin … end frame (“compound statement”).

if boolean_condition then
begin
    statement_zero;
    statement_one;
    statement_two;
end;

Usage

In order to optimize for speed in an if … then … else branch, try to write your expression so that the then-part gets executed most often. This improves the rate of successful jump predictions.

See also

• Official documentation: Reference guide: § “The If..then..else statement”
• Basic Pascal Tutorial/Chapter 3/IF, Tao Yue, Basic Pascal Introduction
• [[;|If statement and semicolon]]
• case

From the Free Pascal wiki, page "If and Then", as it stood on 2023-01-25 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's Licensing page. If you have concerns about this material, message the admin.