GLSL Spec

4 Variables and Types
There are no implicit array or structure conversions. For example, an array of int cannot be implicitly
converted to an array of float.
When an implicit conversion is done, it is not a re-interpretation of the expression's bit pattern, but a
conversion of its value to an equivalent value in the new type. For example, the integer value -5 will be
converted to the floating-point value -5.0. Integer values having more bits of precision than a floating
point mantissa will lose precision when converted to float.
When performing implicit conversion for binary operators, there may be multiple data types to which the
two operands can be converted. For example, when adding an int value to a uint value, both values can
be implicitly converted to uint, float, and double. In such cases, a floating-point type is chosen if either
operand has a floating-point type. Otherwise, an unsigned integer type is chosen if either operand has an
unsigned integer type. Otherwise, a signed integer type is chosen. If operands can be implicitly converted
to multiple data types deriving from the same base data type, the type with the smallest component size is
used.
The conversions in the table above are done only as indicated by other sections of this specification.
4.1.11 Initializers
At declaration, an initial value for an aggregate variable may be provided, specified as an equals (=)
followed by an initializer. The initializer is either an assignment-expression or a list of initializers
enclosed in curly braces. The grammar for the initializer is:
initializer :
assignment-expression
{ initializer-list }
{ initializer-list , }
initializer-list :
initializer
initializer-list , initializer
The assignment-expression is a normal expression except that a comma ( , ) outside parentheses is
interpreted as the end of the initializer, not as the sequence operator. As explained in more detail below,
this allows creation of nested initializers: The aggregate and its initializer must exactly match in terms of
nesting, number of components/elements/members present at each level, and types of
components/elements/members.
An assignment-expression in an initializer must be either the same type as the object it initializes or be a
type that can be converted to the object's type according to section 4.1.10 "Implicit Conversions". Since
these include constructors, an aggregate can be initialized by either a constructor or an initializer list; an
element in an initializer list can be a constructor.
If an initializer is a list of initializers enclosed in curly braces, the variable being declared must be a
vector, a matrix, an array, or a structure.
int i = { 1 };
// illegal, i is not an aggregate
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