Difference between revisions of "Category:LSL Float"

Revision as of 19:53, 22 July 2012

LSL Portal

Floating point data types are 32 bit numbers in IEEE-754 form. If you want a decimal point in your number, then it is a float.

The range is 1.175494351E-38 to 3.402823466E+38

They can be specified in scientific notation like 2.6E-5.

If a function requires a float as a parameter, and the number is an integer (e.g. 5), be sure to add a .0 so it is created as a float (e.g. 5.0)

If you are dividing 2 constants, be sure to define them as floats or your result may get rounded. Better yet, do the math on your calculator and save the server some cycles.

Examples

<lsl>float min = 1.175494351E-38; float max = 3.402823466E+38; float sci = 2.6E-5; float sci_a = 2.6E+3; float sci_b = 2.6E3; float sci_c = 26000.E-1; float f = 2600;//implicitly typecast to a float float E = 85.34859; float Infintity = (float)"inf"; //-- may be negative, will cause a math error if evaluated in LSO, see 'caveats' below float NotANumber = (float)"nan"; //-- may be negative, will cause a math error if evaluated in LSO, see 'caveats' bleow </lsl>

Useful Snippets

If you need to validate an arbitrary float without limitations then the following function is ideal: <lsl>integer isValidFloat(string s) { return (string)((float)s) != (string)((float)("-" + llStringTrim(s, STRING_TRIM_HEAD))); }</lsl>

However, the following is more efficient, but comes with the noted caveats. If these are not an issue to you then it is the recommended option, particularly under Mono: <lsl>integer isValidFloat(string s) { return (float)(s + "1") != 0.0; }</lsl> Caveats:

Under LSO-LSL scientific notation with an exponent greater than 38 will fail (throw a Math Error). Mono is unaffected as it supports infinity
Under both Mono and LSO-LSL you may find strange results if dealing with strings containing more than 9 decimal places. Remember that string casting in LSL only gives up to 6 so is safe, and human input is rarely going to be that accurate, plus values that small are not usually all that useful.
"nan", "inf" and their negatives are special text values that can be cast from a string (with any leading spaces or trailing characters). those values will cause a math error when the variable is evaluated in LSO. If you are parsing user data, by casting a string to a float, use the following code (replacing vStrDta with your string variable name) see SVC-6847
- <lsl>(float)llList2String( llParseStringKeepNulls( llToLower( llStringTrim( vStrDta, STRING_TRIM ) ), ["inf", "nan"], [] ), 0 )</lsl>

Float-to-String

There are several ways to convert a float to a string. The first of which is to typecast it to a string (string)(1.0). This however has the disadvantage of rounding and being limited to six decimal places. Several functions have been written to provide more options. They fall into two categories, lossless and lossy.

Lossy functions
Name	inf/nan	Rounding	Truncation	Notes
Typecast	Yes	Yes	No	`(float)float_value`
Format Decimal	No	Yes	No
Float2String	No	Yes	Yes

Lossless functions
Name	Speed	Reversible	inf/nan support	PI	Notes
Float2Hex	Fast	`(float)`	No	0x6487ED5p-25	Since the output is in the Hexadecimal Scientific Notation, it's not really human readable.
Float2Sci	Slow	`(float)`	No	3.1415925	Useful when you want the result to be lossless but also human readable, comes at the cost of speed.
FUIS	Fastest	SIUF	No	"QEkP2g"	Not at all human readable. Guarantied to always use six characters.

Infinity is only accessible in Mono.

String -to-Float

String2Float

Generates float output from an equivalent string

Subcategories

This category has only the following subcategory.

F

LSL Functions/Returns a float

Pages in category "LSL Float"

The following 8 pages are in this category, out of 8 total.

D

DEG TO RAD

F

@@ Line 109: / Line 109: @@
 *Infinity is only accessible in Mono.
 </div></div>
+<div id="box">
+== String -to-Float ==
+{|{{Prettytable}}
+|-
+|| [[String2Float]] || Generates float output from an equivalent string
+|-}
+</div>