Difference between revisions of "Typecast"

Latest revision as of 08:49, 30 May 2024

LSL Portal

To convert the type of a value a typecast is required. There are two types of typecasting, explicit and implicit. Explicit typecasts must be provided by the programmer, but implicit typecasts are put in place by the compiler. LSL implicitly typecasts strings to keys and integers to floats where the latter type is required but the former is provided.

Supported Typecasts
		To
		integer	float	string	key	list	vector	rotation
From	integer	x	x	x		x
	float	x	x	x		x
	string	x	x	x	x	x	x	x
	key			x	x	x
	list			x		x
	vector			x		x	x
	rotation			x		x		x

Syntax: (type)value

Converts value to type.

• expression	type	–	variable type
• expression	value	–	expression or constant

If value is a complex expression, it may be beneficial to wrap it in parentheses. (type)(value)

Examples

string a = "1.5";
float b = (float)a;
integer c = (integer)a;

integer i;
i = (integer) 1.23;     // 1
i = (integer) -1.23;    // -1
i = (integer) "0123";   // 123
i = (integer) "0x12A";  // 298
i = (integer) "   -5  ";  // -5; leading white space is ignored
i = (integer) "105 degrees here, it is a nice day"; // 105; non-numeric text which follows numeric text is ignored
i = (integer) "String with no numbers"; // 0

float f;
f = (float) "6.2e1";   // 62.0
f = (float) "  -16.2°C is seriously cold!"; // -16.2; (float)string also ignores leading whitespace and trailing non-numeric characters
// "6.2e1", "6.2e+1", "6.2E1", "6.2E+1" are all equivalent.
f = (float) "0x1.f";    // 1.9375; hexadecimal floats in style of the C99 standard are accepted
f = (float) "0x0.3p-2"; // 0.046875 = 0.1875 * 2^-2; the "p" exponent uses base 2, and unlike C99 is not mandatory
f = (float) "Nancy";   // any string beginning with "nan" (case insensitive) --
                       //   Mono only: NaN (not a number); LSO: causes a math error
f = (float) "infallible LSL!";   // any string beginning with "inf" (case insensitive) --
                                 //   Mono only: Infinity; LSO: causes a math error

string s;
s = (string) -PI;              // "-3.141593" with precision set to 6 decimal places by zero padding or rounding
s = (string) [1, 2.3, "a"];    // "12.300000a" again 6 decimal places, but ...
s = (string) <1.0, 2.3, 4.56>; // "<1.00000, 2.30000, 4.56000>" .. now with precision set to 5 decimal places
s = (string) <2, 4, 0.0, PI >;  // "<2.00000, 4.00000, 0.00000, 3.14159>"

list l;
l = (list) "";                // [""]
l = (list) <1.0, 2.3, 4.56>;  // ["<1.00000, 2.30000, 4.56000>"]

vector v;
v = (vector) "<1.0, 2.3, 4.56>";  // <1.0, 2.3, 4.56>
v = (vector) "<1.0, 2.3>";        // ZERO_VECTOR  (Due to insufficient value)

rotation r;
r = (rotation) "<1.0, 2.3, 4.56, 1.0>";  // <1.0, 2.3, 4.56, 1.0>
r = (rotation) "<1.0, 2.3, 4.56>";       // ZERO_ROTATION  (Due to insufficient value)

Applied

default
{
    state_entry()
    {
        integer iUnixTime   = llGetUnixTime(); 
        string  sUnixTime   = (string)unixTime;
        string  sRegionTime = (string)llGetTimeOfDay();
        llSetObjectDesc(sUnixTime);
        llSetText(sRegionTime, <1.0, 0.0 ,0.0>, 1.0);
    }
}

Caveats

The compiler allows explicit typecasting where it is not needed and does not optimize it out. Unnecessary typecasts will bloat code and slow it down.

Notes

Typecasting from a float to an integer merely removes the portion of the number following the decimal point. To round to the nearest whole integer, use llRound.
For getting at the elements of a list use the llList2* functions.
For casting a variable myVar to a single-item list, the syntax (list)myVar is about 30% more efficient under LSL Mono than the syntax [myVar]. The same (list)myVar syntax is also slightly more efficient under LSL-LSO.