Difference between revisions of "Category:LSL Float"
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Revision as of 14:19, 23 August 2012
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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 cast = (float)"42";//explicit typecast to a float 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.
| Name | inf/nan | Rounding | Truncation | Notes |
|---|---|---|---|---|
| Typecast | Yes | Yes | No | (float)float_valueMono only gives 6 digits of precision. |
| Format Decimal | No | Yes | No | |
| Float2String | No | Yes | Yes |
| 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.
Pages in category "LSL Float"
The following 8 pages are in this category, out of 8 total.