# if...else语句 函数

if 语句后可以跟可选的 else 语句，该语句在布尔表达式为false时执行。

## if...else statement - 语法

Lua编程语言中的 if ... else 语句的语法是-

```if(boolean_expression)
then
--[ statement(s) will execute if the boolean expression is true --]
else
--[ statement(s) will execute if the boolean expression is false --]
end```

## if...else statement - 示例

```--[ local variable definition --]
a=100;

--[ check the boolean condition --]

if( a < 20 )
then
--[ if condition is true then print the following --]
print("a is less than 20" )
else
--[ if condition is false then print the following --]
print("a is not less than 20" )
end

print("value of a is :", a)```

```a is not less than 20
value of a is :	100```

## if...else statement - else if ... else语句

if 语句后可以跟可选的 else if ... else 语句，这对于使用单个if ... else if语句测试各种条件非常有用。

Lua编程语言中的 if ... else if ... else 语句的语法是-

```if(boolean_expression 1)
then
--[ Executes when the boolean expression 1 is true --]

else if( boolean_expression 2)
--[ Executes when the boolean expression 2 is true --]

else if( boolean_expression 3)
--[ Executes when the boolean expression 3 is true --]
else
--[ executes when the none of the above condition is true --]
end```

## if...else statement - 示例

```--[ local variable definition --]
a=100

--[ check the boolean condition --]

if( a == 10 )
then
--[ if condition is true then print the following --]
print("Value of a is 10" )
elseif( a == 20 )
then
--[ if else if condition is true --]
print("Value of a is 20" )
elseif( a == 30 )
then
--[ if else if condition is true  --]
print("Value of a is 30" )
else
--[ if none of the conditions is true --]
print("None of the values is matching" )
end
print("Exact value of a is: ", a )```

```None of the values is matching
Exact value of a is:	100```

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