Difference between revisions of "If and Then"
From Lazarus wiki
Jump to navigationJump to searchm (Text replacement - "Object Pascal Introduction" to "Basic Pascal Introduction") |
(remove “back to <some random page>” link, as there are multiple pages linking here; substitute legacy syntaxhighlight syntax) |
||
Line 1: | Line 1: | ||
{{then}} | {{then}} | ||
+ | The <syntaxhighlight lang="pascal" inline>if</syntaxhighlight> [[Keyword|keyword]] precedes a condition, must be followed by <syntaxhighlight lang="pascal" inline>then</syntaxhighlight> and a statement. | ||
+ | The statement may optionally be followed by [[Else|<syntaxhighlight lang="pascal" inline>else</syntaxhighlight>]] and another statement. | ||
− | + | == <syntaxhighlight lang="pascal" inline>If then</syntaxhighlight> == | |
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
<syntaxhighlight lang="pascal"> | <syntaxhighlight lang="pascal"> | ||
Line 16: | Line 12: | ||
</syntaxhighlight> | </syntaxhighlight> | ||
− | <syntaxhighlight lang="pascal" | + | <syntaxhighlight lang="pascal" inline>condition</syntaxhighlight> is a [[Boolean|<syntaxhighlight lang="pascal" inline>boolean</syntaxhighlight>]] expression that evaluates to [[True|<syntaxhighlight lang="pascal" inline>true</syntaxhighlight>]] xor [[False|<syntaxhighlight lang="pascal" inline>false</syntaxhighlight>]]. |
− | <syntaxhighlight lang="pascal" | + | <syntaxhighlight lang="pascal" inline>true_statement</syntaxhighlight> is executed if <syntaxhighlight lang="pascal" inline>condition</syntaxhighlight> evaluates to <syntaxhighlight lang="pascal" inline>true</syntaxhighlight>. |
− | <syntaxhighlight lang="pascal" | + | <syntaxhighlight lang="pascal" inline>false_statement</syntaxhighlight> is executed if <syntaxhighlight lang="pascal" inline>condition</syntaxhighlight> evaluates to <syntaxhighlight lang="pascal" inline>false</syntaxhighlight>. |
− | A compile-time error occurs if the type of <syntaxhighlight lang="pascal" | + | A compile-time error occurs if the type of <syntaxhighlight lang="pascal" inline>condition</syntaxhighlight> does not evaluate to a <syntaxhighlight lang="pascal" inline>boolean</syntaxhighlight> value. |
− | === Multiple statements in <syntaxhighlight lang="pascal" | + | === Multiple statements in <syntaxhighlight lang="pascal" inline>if then</syntaxhighlight> branch === |
− | If you need two or more statements for <syntaxhighlight lang="pascal" | + | If you need two or more statements for <syntaxhighlight lang="pascal" inline>true_statement</syntaxhighlight> or <syntaxhighlight lang="pascal" inline>false_statement</syntaxhighlight>, enclose them within a [[Begin|<syntaxhighlight lang="pascal" inline>begin</syntaxhighlight>]] … [[End|<syntaxhighlight lang="pascal" inline>end</syntaxhighlight>]] [[Block]] (compound statement). |
<syntaxhighlight lang="pascal"> | <syntaxhighlight lang="pascal"> | ||
Line 35: | Line 31: | ||
== See also == | == See also == | ||
− | * Official documentation: [https://www.freepascal.org/docs-html/ref/refsu57.html Reference guide: § “The <syntaxhighlight lang="pascal" | + | * 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 | * [[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" | + | * [[Case|<syntaxhighlight lang="pascal" inline>case</syntaxhighlight>]] |
{{Keywords}} | {{Keywords}} |
Revision as of 05:52, 16 May 2020
│
Deutsch (de) │
English (en) │
français (fr) │
русский (ru) │
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.
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
Block (compound statement).
if boolean_condition then
begin
statement_zero;
statement_one;
statement_two;
end;
See also
- Official documentation: Reference guide: § “The
If..then..else
statement” - IF, Tao Yue, Basic Pascal Introduction
- If statement and semicolon
case
Keywords: begin — do — else — end — for — if — repeat — then — until — while