逻辑函数

### if

Returns one of two values depending on a condition.
Parameters:

- `condition`: A boolean expression
- `value1`: A value returned if condition is true.
- `value2`: A value returned if condition is not true.

Released: v3.0.0 Updated: v3.6.0

#### Examples:

```less
@some: foo;

div {
    margin: if((2 > 1), 0, 3px);
    color:  if((iscolor(@some)), @some, black);
}
```
#### Result:

```less
div {
    margin: 0;
    color:  black;
}
```
**Notes:** A boolean expression supported as the conditional parameter are the same as of Guard Statements.

```less
if(not (true), foo, bar);
if((true) and (2 > 1), foo, bar);
if((false) or (isstring("boo!")), foo, bar);
```
**Note:** before Less 3.6, the condition required a set of parentheses.

```less
if(2 > 1, blue, green);   // Causes an error in 3.0-3.5.3
if((2 > 1), blue, green); // Ok 3.0+
```
### boolean

Evaluates to true or false
You can "store" a boolean test for later evaluation in a guard or if().

Parameters:

- `condition`: A boolean expression

Released: v3.0.0 Updated: v3.6.0

#### Examples:

```less
@bg: black;
@bg-light: boolean(luma(@bg) > 50%);

div {
  background: @bg; 
  color: if(@bg-light, black, white);
}
```
#### Result:

```less
div {
  background: black;
  color: white;
}
```