If and Then
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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
Keywords: begin — do — else — end — for — if — repeat — then — until — while