Difference between revisions of "If and Then"
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{{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 | ||
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</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 | ||
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== 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..elsestatement” - IF, Tao Yue, Object Pascal Introduction
- If statement and semicolon
Keywords: begin — do — else — end — for — if — repeat — then — until — while
