Difference between revisions of "If and Then"
From Lazarus wiki
Jump to navigationJump to search (better syntax highlighting) |
|||
Line 1: | Line 1: | ||
{{If}} | {{If}} | ||
− | The < | + | The <syntaxhighlight lang="pascal" enclose="none">if</syntaxhighlight> [[Keyword|keyword]] precedes a condition, must be followed by [[Then|<syntaxhighlight lang="pascal" enclose="none">then</syntaxhighlight>]] and a statement. |
+ | The statement may optionally be followed by [[Else|<syntaxhighlight lang="pascal" enclose="none">else</syntaxhighlight>]] and another statement. | ||
− | == < | + | == <syntaxhighlight lang="pascal" enclose="none">If then</syntaxhighlight> == |
− | <syntaxhighlight> | + | <syntaxhighlight lang="pascal"> |
if condition | if condition | ||
then true_statement | then true_statement | ||
Line 12: | Line 13: | ||
</syntaxhighlight> | </syntaxhighlight> | ||
− | < | + | <syntaxhighlight lang="pascal" enclose="none">condition</syntaxhighlight> is a [[Boolean|<syntaxhighlight lang="pascal" enclose="none">boolean</syntaxhighlight>]] expression that evaluates to [[True|<syntaxhighlight lang="pascal" enclose="none">true</syntaxhighlight>]] xor [[False|<syntaxhighlight lang="pascal" enclose="none">false</syntaxhighlight>]]. |
− | < | + | <syntaxhighlight lang="pascal" enclose="none">true_statement</syntaxhighlight> is executed if <syntaxhighlight lang="pascal" enclose="none">condition</syntaxhighlight> evaluates to <syntaxhighlight lang="pascal" enclose="none">true</syntaxhighlight>. |
− | < | + | <syntaxhighlight lang="pascal" enclose="none">false_statement</syntaxhighlight> is executed if <syntaxhighlight lang="pascal" enclose="none">condition</syntaxhighlight> evaluates to <syntaxhighlight lang="pascal" enclose="none">false</syntaxhighlight>. |
− | A compile-time error occurs if the type of < | + | A compile-time error occurs if the type of <syntaxhighlight lang="pascal" enclose="none">condition</syntaxhighlight> does not evaluate to a <syntaxhighlight lang="pascal" enclose="none">boolean</syntaxhighlight> value. |
− | === Multiple statements in < | + | === Multiple statements in <syntaxhighlight lang="pascal" enclose="none">if then</syntaxhighlight> branch === |
− | If you need two or more statements for < | + | If you need two or more statements for <syntaxhighlight lang="pascal" enclose="none">true_statement</syntaxhighlight> or <syntaxhighlight lang="pascal" enclose="none">false_statement</syntaxhighlight>, enclose them within a [[Begin|<syntaxhighlight lang="pascal" enclose="none">begin</syntaxhighlight>]] … [[End|<syntaxhighlight lang="pascal" enclose="none">end</syntaxhighlight>]] [[Block]] (compound statement). |
− | <syntaxhighlight> | + | <syntaxhighlight lang="pascal"> |
if boolean_condition then | if boolean_condition then | ||
begin | begin | ||
Line 34: | Line 35: | ||
== See also == | == See also == | ||
− | * Official documentation: [https://www.freepascal.org/docs-html/ref/refsu57.html Reference guide: § “The < | + | * Official documentation: [https://www.freepascal.org/docs-html/ref/refsu57.html Reference guide: § “The <syntaxhighlight lang="pascal" enclose="none">If..then..else</syntaxhighlight> statement”] |
* [[IF]], Tao Yue, Object Pascal Introduction | * [[IF]], Tao Yue, Object Pascal Introduction | ||
* [[;#If statement and semicolon|If statement and semicolon]] | * [[;#If statement and semicolon|If statement and semicolon]] |
Revision as of 18:42, 11 February 2018
│
English (en) │
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, Object Pascal Introduction
- If statement and semicolon
Keywords: begin — do — else — end — for — if — repeat — then — until — while