Difference between revisions of "If"

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(Added info on specifying how many lines are to be evaluted.)
 
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{{command header|Flow Control}}
 
{{command header|Flow Control}}
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{{body|if ( expression ) { }|The ''if'' construct is one of the most important feature of many languages, the EasyUO scripting language included. It allows for conditional execution of code fragments.
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{{body|if ( ! ) ( expression ) ( lines <nowiki>|</nowiki> { } )
  
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As described in the section about expressions ''expression'' is evaluated to its boolean value. If it evaluates to [[true]] the statement will be executed.
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:''or''
  
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The following code fragment will display <b>a is bigger than b</b> if %a is bigger than %b:
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if ( ! ) ( expression ) ( lines <nowiki>|</nowiki> { } ) else ( lines <nowiki>|</nowiki> { } ) |The <tt>if</tt> construct is one of the most important features of many languages, the EasyUO scripting language included. It allows for conditional execution of code fragments.
 +
 
 +
As described in the section about [[expressions]], <tt>expression</tt> is evaluated to its boolean value. If it evaluates to [[true]], the next statement will be executed. If <tt>else</tt> is present and the expression evaluates to [[false]], then the statement after <tt>else</tt> will be executed instead.
 +
 
 +
If <tt>%a > %b</tt> evaluates to [[true]] in the following code fragment, it will display <i>"a is bigger than b"</i>; if it evaluates to [[false]], <i>"a is equal or less than b"</i> will be displayed instead:
 
<pre>
 
<pre>
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set %a 1
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set %a 100
−
set %b 0
+
set %b #random
 
if %a > %b
 
if %a > %b
 
display ok a is bigger than b
 
display ok a is bigger than b
 +
else
 +
display ok a is equal or less than b
 +
halt
 
</pre>
 
</pre>
−
Often you would want to have more than one statement executed conditionally. Of course, there is no need to wrap each statement in an if clause. Instead, you can group several statements into a statement group. For example, this code would display a is bigger than b if %a is bigger than %b, and would then assign the value of %a into %b:
+
Often you would want to have more than one statement executed conditionally. Of course, there is no need to wrap each statement in an if clause. Instead, you have two options. You can group several statements into a statement group or you can specify how many lines after the if statement are to be evaluated. For example, if <tt>%a > %b</tt> evaluates to [[true]] in the following fragment, it would display <i>"a is bigger than b"</i> and would then assign the value of <tt>%a</tt> into <tt>%b</tt>; if it evaluates to [[false]], <i>"b is equal or bigger than a"</i> would be displayed and the value of <tt>%b</tt> assigned into <tt>%a</tt> instead:
 
<pre>
 
<pre>
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set %a 10
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set %a 100
−
set %b 2
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set %b #random
 
if %a > %b
 
if %a > %b
 
{
 
{
Line 20: Line 27:
 
set %b %a
 
set %b %a
 
}
 
}
 +
else
 +
{
 +
display ok b is equal or bigger than a
 +
set %a %b
 +
}
 +
halt
 
</pre>
 
</pre>
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''if'' statements can be nested indefinitely within other [[if]] statements, which provides you with complete flexibility for conditional execution of the various parts of your script.}}
 
  
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==== Example ====
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OR
 +
 
 
<pre>
 
<pre>
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if #charposx > #charposy
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set %a 100
 +
set %b #random
 +
if %a > %b 2
 +
 
 +
display ok a is bigger than b
 +
set %b %a
 +
else 2
 +
display ok b is equal or bigger than a
 +
set %a %b
 +
halt
 +
</pre>
 +
 
 +
 
 +
The ! right after the command is a reversal of the expression which is following.
 +
<pre>
 +
set %var hello
 +
if %var = world
 +
display ok This shouldnt be displayed.
 +
if %var <> world
 +
display ok This should be displayed because hello is another (<>) than world.
 +
if ! %var = world
 +
display ok this should be displayed because hello is not equal world.
 +
stop</pre>}}
 +
 
 +
 
 +
 
 +
 
 +
==== Nesting Conditional Statements ====
 +
<tt>if</tt> statements can be nested indefinitely within other <tt>if</tt> or <tt>else</tt> statements, which provides you with complete flexibility for conditional execution of the various parts of your script.
 +
<pre>
 +
set %a #random % 3 + 1
 +
if %a = 1
 +
{
 +
  display ok One
 +
}
 +
else
 
{
 
{
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display ok You are farther East than you are South!
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  if %a = 2
−
halt
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  {
 +
    display ok Two
 +
  }
 +
  else
 +
  {
 +
    display ok Three
 +
  }
 
}
 
}
 +
halt
 
</pre>
 
</pre>
  
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{{footer}}
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== Related Commands ==
 +
{| style="background:gainsboro; color:black; border: 2px #aaa solid;"
 +
| Width=250px align=center | [[Else]]
 +
|}
 +
=See Also=
 +
{{Flow Control}}

Latest revision as of 09:46, 30 November 2008

Synopsis

if ( ! ) ( expression ) ( lines | { } )

or

if ( ! ) ( expression ) ( lines | { } ) else ( lines | { } )

Description

The if construct is one of the most important features of many languages, the EasyUO scripting language included. It allows for conditional execution of code fragments.

As described in the section about expressions, expression is evaluated to its boolean value. If it evaluates to true, the next statement will be executed. If else is present and the expression evaluates to false, then the statement after else will be executed instead.

If %a > %b evaluates to true in the following code fragment, it will display "a is bigger than b"; if it evaluates to false, "a is equal or less than b" will be displayed instead: 

set %a 100
set %b #random
if %a > %b
	display ok a is bigger than b
else
	display ok a is equal or less than b
halt

Often you would want to have more than one statement executed conditionally. Of course, there is no need to wrap each statement in an if clause. Instead, you have two options. You can group several statements into a statement group or you can specify how many lines after the if statement are to be evaluated. For example, if %a > %b evaluates to true in the following fragment, it would display "a is bigger than b" and would then assign the value of %a into %b; if it evaluates to false, "b is equal or bigger than a" would be displayed and the value of %b assigned into %a instead: 

set %a 100
set %b #random
if %a > %b
{
	display ok a is bigger than b
	set %b %a
}
else
{
	display ok b is equal or bigger than a
	set %a %b
}
halt

OR 

set %a 100
set %b #random
if %a > %b 2

	display ok a is bigger than b
	set %b %a
else 2
	display ok b is equal or bigger than a
	set %a %b
halt


The ! right after the command is a reversal of the expression which is following. 

set %var hello 
if %var = world 
	display ok This shouldnt be displayed. 
if %var <> world 
	display ok This should be displayed because hello is another (<>) than world. 
if ! %var = world 
	display ok this should be displayed because hello is not equal world. 
stop



Nesting Conditional Statements

if statements can be nested indefinitely within other if or else statements, which provides you with complete flexibility for conditional execution of the various parts of your script. 

set %a #random % 3 + 1
if %a = 1
{
  display ok One
}
else
{
  if %a = 2
  {
    display ok Two
  }
  else
  {
    display ok Three
  }
}
halt

Related Commands

Else

See Also

Flow Control

  • Flow control commands allow scripts to make decisions based on the evaluation of boolean expressions.
break Jumps to first statement outside of loop
call Transfers execution to another script file
continue Jumps execution of a loop to next iteration
exit Exits a called script
for Creates a counting loop
gosub Transfers execution to the matching sub
goto Jumps to another part of the script given by a label
halt Stops the script
if Executes code based on the evaluation of an expression
pause Temporarily stops the execution of the current script
repeat..until Creates a loop that checks condition after execution
return Returns from a sub
stop Ends the script
while Creates a loop that checks condition before execution
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