MEL Programming Basics

• Special Characters:
• \" - Used when a quotation mark needs to be part of a string
• \r - Used to add a carriage return into a string
  
• \t - Used to add a tab into a string
  
• \n - Used to add a new line feed into a string
  
• \\ - Used to add a backslash into a string. Mostly used for system paths

• Data types (cont'd):
• Array
• A zero-based series of variables stored in a single variable container
• Denoted by braces [ ] at the end of the variable name
• Each element is seperated by a comma
  
• All variable types in the array must be of the same data type
• Size is dynamic and expands as you add more elements
• Syntax:
1. float $myArray[] = { 0.3, 6.325, 71.6 };
2. print $myArray[1]; // Result: 6.325 //
• Matrix
• A zero-based two dimensional array that holds floating point numbers
  
• Denoted by double braces [ ] [ ] at the end of the variable name containing the number of rows and columns
  
• Each row is seperated by a semi-colon while each column is seperated by a comma
  
• Size is static and must be initialized when created
• Syntax:
1. matrix $myMatrix[3][4] = << 1.3, 0.25, 3.625, 2.25; 41.2, 15.625, 6.335, 23.63; 2.228, 32.3, 54.2, 0.352 >>;
2. print $myMatrix[2][1]; // Result: 32.3 //

• Casting Values:
• Backticks are used when capturing a command return value.
• Remember to use the accent key ( ` ), located in the top left corner on your keyboard, and not the the apostrophe key ( ' ).
  

• Operators:
• All data on the right side of the operator is evaluated first, and then applied to the variable on the left side of the operator
• Operators use basic math "nesting" styles in determining evaluation order
• ((3 + 4) * 6) / 2 would result in 21 but 3 + (4 * 6) / 2 would result in 15
  
• Assignment Oerators: ( = )
• Used to set two items equal to eachother
  
• Syntax:
1. int $temp = 5;
• Arithmetic Operators: ( +, -, *, / )
• Basic math functionality
• Syntax:
1. int $myAddInt = 5 + 1; // Result: $myAddInt = 6 //
2. float $mySubFloat = 6 - 1.7; // Result: $mySubFloat = 4.3 //
3. float $myMultFloat = 16 * 3.31; // Result: $myMultFloat = 52.96 //
4. float $myDivFloat = 2.25 / 1.3; // Result: $myDivFloat = 1.730769 //
• Note: When using the division arithmetic operator, at least one of the numbers ( numerator or denominator ) must contain a decimal point.
1. float $myDivFloat = 3 / 2; // Result: $myDivFloat = 1 //
2. float $myDivFloat = 3.0 / 2; // Result: $myDivFloat = 1.5 //
3. float $myDivFloat = 3 / 2.0; // Result: $myDivFloat = 1.5 //
• In-place Arithmetic Operators: ( +=, -=, *=, /= )
• Changes value to an item
• Syntax:
1. int $temp = 1;
2. $temp += 5; // Result: $temp = 6 //
3. $temp *= 3;  // Result: $temp = 18 //
4. $temp /= 2; // Result: $temp = 9 //
• Increment and Decrement Operators: ( ++, -- )
• ++ adds 1 to the value of an item
• -- subtracts 1 from the value of an item
• Syntax:
  
1. $temp++; ( post-operation +1 after the entire line is executed )
2. ++$temp; (pre-operation +1 before the entire line is executed )
3. $temp--; ( post-operation -1 after the entire line is executed )
4. --$temp; ( pre-operation -1 before the entire line is executed )
• Modulous Operator: ( % )
• Used to find the remainder of division in integers
• Syntax:
1. int $val1 = 26;
2. int $val2 = 8;
3. int $modVal = $val1 % $val2; // Result: $modVal = 2 //
   
• Relational Operators: ( <, <=, >, >=, ==, != )
• Tests relationship conditions in if statements
• < Less than
• <= Less than or equal to
• > Greater than
• >= Greater than or equal to
• == Equal to ( Note: Do not confuse with assignment = operator )
  
• != Not equal to
• Syntax:
1. int $a = 3;
2. int $b = 4;
   
• if ( $a < $b ) // Results in a true statement //
• if ( $a == $b ) // Results in a false statement //
• if ( $a != $b ) // Results in a true statement //
• Logical Operators: ( &&, ||, ! )
• Tests conditions in if statements
• && And - Needs both evaluations to be true
  
• || Or - Needs at least one evaluation to be true
  
• ! Not - Toggles the current state
  
• Syntax:
1. int $a = false;
2. int $b = true;
• if ( $a && $b ) // Results in false statement //
• if ( $a || $b ) // Results in true statement //
• if ( !$a ) // Results in true statement //
• Conditional Operator: ( ?: )
• This is a shorthand way of testing a condition and populating a variable depending on the results
• Syntax:
1. int $val1 = 5;
2. int $val2 = 4;
   
3. float $newVal = ( $val1 > $val2 ) ? 13.25 : 36.375; // Result: $newVal = 13.25 //
   
• Operator Order of Precedence:
• Operators in the same precedence group are evaluated from left to right in the order they appear in the statement
• Precedence Groups:
  
1. ( ), [ ]
2. !, ++, --
3. *, /, %, ^
   
4. +, -
5. <. <=, >, >=
6. ==, !=
7. &&
   
8. ||
9. ?:
10. =, +=, -=, *=, /=

• Conditional Statements:
• An action will be performed only if a specified condition is evaluated to be true

• Looping:
• Used for repeating a block of code a specified number of times
  
• While Loop: Repeats a block of code until a "conditionStatement" is no longer evaluated as true

• For Loop: Repeats a block of code until the "valueTest" is no longer evaluated as true

• For-in Loop: Repeats a block of code for each element in an array

• Infinite Loops: Always evaluate as true and never stop looping, causing Maya to lock up and crash!