Difference between revisions of "If and Then"
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== See also == | == See also == | ||
* Official documentation: [https://www.freepascal.org/docs-html/ref/refsu57.html Reference guide: § “The <syntaxhighlight lang="pascal" inline>If..then..else</syntaxhighlight> statement”] | * Official documentation: [https://www.freepascal.org/docs-html/ref/refsu57.html Reference guide: § “The <syntaxhighlight lang="pascal" inline>If..then..else</syntaxhighlight> statement”] | ||
− | * [[IF]], Tao Yue, Basic Pascal Introduction | + | * [[Basic Pascal Tutorial/Chapter 3/IF]], Tao Yue, Basic Pascal Introduction |
* [[;#If statement and semicolon|If statement and semicolon]] | * [[;#If statement and semicolon|If statement and semicolon]] | ||
* [[Case|<syntaxhighlight lang="pascal" inline>case</syntaxhighlight>]] | * [[Case|<syntaxhighlight lang="pascal" inline>case</syntaxhighlight>]] | ||
{{Keywords}} | {{Keywords}} |
Latest revision as of 05:06, 25 January 2023
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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