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MEL and Expressions

Automatic type conversion

Automatic conversion

Maya’s automatic type conversion lets you convert types without explicitly stating them. It also automatically converts the data type for you if the type specified is not acceptable.

Occasionally unexpected automatic type conversions can create a problem. Knowing the rules for type conversion can help you fix these types of errors:

• Strings dominate all other types.
• Vectors dominate floats.
• Floats dominate ints.
• If one operand is an int type and the other is a float type, MEL converts the int to a float.
• Between vector and matrix types, the type on the left-hand side dominates.
• In assignment, the type on the left-hand side dominates.

In an assignment operation, the type of the right-hand side is converted to the type of the left-hand side. The first four rules apply for sub-expressions during the computation of the right-hand side; a final conversion takes place when assigning to the left-hand side.

The following table demonstrates the rules for automatic conversions.

Operation	Resulting data type
int operator float	float
float operator int	float
int operator vector	vector
vector operator float	vector
vector operator matrix	vector
matrix operator vector	matrix
matrix operator string	string
string operator int	string

$var1 = 7 + 1.3;          // Type:  float (8.3) 
$var2 = 7.9 + 2;          // Type:  float (9.9) 
$var3 = 2 + <<4, 5, 6>>;  // Type:  vector <<6, 7, 8>> 
$var4 = 0007 + " Lives!"; // Type:  string ("7 Lives!") 

In the last example, 0007 is an int of value 7, which is converted to a string and concatenated with “Lives!”. The result is a string which implicitly declares var4 to be of type string with value “7 Lives!”.

Explicit conversion

There are two ways to explicitly convert a value of one type to another type. The most common way is to specify the type in parentheses before the value. For example:

$Z = (vector) "<<1, 2, 3>>"; // Type:  vector (<<1, 2, 3>>) 
$cools = (float) 7;         // Type:  float (7) 
$ools = (string) 47.554;    // Type:  string ("47.554") 

You can also explicitly convert a value to another type by specifying the type followed by the value in parentheses. For example:

$ly = vector("<<1, 2, 3>>"); // Type:  vector (<<1, 2, 3>>) 
$ooly = int(3.67);           // Type:  int (3)