Intro to Mel Script Part 7 :: Learning About Conditional Statements

Some of the most common practices in Mel Scripting includes checking if something is true or false.
Or, in other words, how do you simply ask Maya a question? The answer is: "conditional statements".


Conditional statements use symbols to tell the computer if a value is or isn't equal to another value. These symbols are called "Comparison Operators"

Comparison Operators in Mel Script:

<
LESS THAN
A < B
"A" is less than "B"

>
GREATER THAN
A > B
"A" is greater than "B"

<=
LESS THAN OR EQUAL
A <= B
"A" is less than or equal to "B"

>=
GREATER THAN OR EQUAL
A >= B
"A" is greater than or equal to "B"

==
EQUAL TO
A == B
"A" is equal to "B"

!=
NOT EQUAL TO
A != B
"A" is not equal to "B"

 
Here are some examples of what we mean by "conditional statements":

IF 
int $a = 10;
if ($a == 10) {
    print "variable equals 10.\n";
}


IF/ELSE
int $a = 0;
if ($a < 10) {
     print "condition is true.\n";
}
else {
     print "condition is false.\n";
}


IF/ELSE IF
int $a = 8;
if ($a < 10) {
     print "less than 10.\n";
}
else if ( ($a >= 10 ) && ( $a < 20) )  {
     print "greater than or equal to 10 but less than 20.\n";
}
else {
     print "greater or equal to 20.\n";
}


NESTING IF STATEMENTS  
int $a = 2;
if ($a < 10) {
     print "less than 10.\n";
     if ($a < 5) {
          print "also less than 5.\n";
     }
}


SWITCH
int $a = 0;  
switch ($a) {
     case 1:
          print "equals 1\n";
          break;
     case 5:
          print "equals 5\n";
          break;
     case 10:
          print "equals 10\n";
          break;
     default:
          print "didnt match any above\n";
          break;
}