Difference between revisions of "Category:LSL Float"
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Lady Sumoku (Talk  contribs) m (Replaced old <LSL> block with <source lang="lsl2">) 

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== Examples ==  == Examples ==  
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−  <  +  <source lang="lsl2">float min = 1.175494351E38; 
float max = 3.402823466E+38;  float max = 3.402823466E+38;  
float sci = 2.6E5;  float sci = 2.6E5;  
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float Infintity = (float)"inf"; // may be negative, will cause a math error if evaluated in LSO, see 'caveats' below  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  float NotANumber = (float)"nan"; // may be negative, will cause a math error if evaluated in LSO, see 'caveats' bleow  
−  </  +  </source> 
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If you need to validate an arbitrary float without limitations then the following function is ideal:  If you need to validate an arbitrary float without limitations then the following function is ideal:  
−  <  +  <source lang="lsl2">integer isValidFloat(string s) { return (string)((float)s) != (string)((float)("" + llStringTrim(s, STRING_TRIM_HEAD))); }</source> 
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:  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:  
−  <  +  <source lang="lsl2">integer isValidFloat(string s) { return (float)(s + "1") != 0.0; }</source> 
The above snippets are of limited use, as they stop validating at the first character that is not valid in a float string. The following code rigorously validates the whole of a string to ensure it represents a float.  The above snippets are of limited use, as they stop validating at the first character that is not valid in a float string. The following code rigorously validates the whole of a string to ensure it represents a float.  
−  <  +  <source lang="lsl2"> 
// Validate a string containing a float value  // Validate a string containing a float value  
// Does not handle scientific notation, or hex floats (!!)  // Does not handle scientific notation, or hex floats (!!)  
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return TRUE;  return TRUE;  
}  }  
−  </  +  </source> 
'''Caveats''':  '''Caveats''':  
* Under LSOLSL scientific notation with an exponent greater than 38 will fail (throw a Math Error). Mono is unaffected as it supports <code>infinity</code>  * Under LSOLSL scientific notation with an exponent greater than 38 will fail (throw a Math Error). Mono is unaffected as it supports <code>infinity</code>  
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* Due to the limited precision with which floats are stored, not all integer values can be accurately held in a float. Integers above 16,777,216 are rounded down to the nearest even number; above 33,554,432 to the lower multiple of 4 etc.  * Due to the limited precision with which floats are stored, not all integer values can be accurately held in a float. Integers above 16,777,216 are rounded down to the nearest even number; above 33,554,432 to the lower multiple of 4 etc.  
* "nan" (notanumber), "inf" (infinity) 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 [https://jira.secondlife.com/browse/SVC6847 SVC6847]  * "nan" (notanumber), "inf" (infinity) 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 [https://jira.secondlife.com/browse/SVC6847 SVC6847]  
−  ** <  +  ** <source lang="lsl2">(float)llList2String( llParseStringKeepNulls( llToLower( llStringTrim( vStrDta, STRING_TRIM ) ), ["inf", "nan"], [] ), 0 )</source> 
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Revision as of 02:52, 22 January 2015
LSL Portal  Functions  Events  Types  Operators  Constants  Flow Control  Script Library  Categorized Library  Tutorials 
Contents
The LSL "float" type is a floating point data type that uses 32 bit in IEEE754 form. If a number is written with a decimal point in LSL, then it is taken to be a float.
The valid range is 1.401298464E45 to 3.402823466E+38
Floats can be specified in scientific notation such as 2.6E5.
If a function requires a float as a parameter, and the number is an integer (e.g. 5), you can add the .0 to clearly indicate it's a float, but omitting the .0 is equally valid and actually saves bytecode space in the compiled code.
When dividing 2 constants, defining them as floats will avoid the chance of unwanted rounding down. Better still, do the math on your calculator and save the server some cycles.
Examples
float min = 1.175494351E38; float max = 3.402823466E+38; float sci = 2.6E5; float sci_a = 2.6E+3; float sci_b = 2.6E3; float sci_c = 26000.E1; 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
Useful Snippets
If you need to validate an arbitrary float without limitations then the following function is ideal:
integer isValidFloat(string s) { return (string)((float)s) != (string)((float)("" + llStringTrim(s, STRING_TRIM_HEAD))); }
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:
integer isValidFloat(string s) { return (float)(s + "1") != 0.0; }
The above snippets are of limited use, as they stop validating at the first character that is not valid in a float string. The following code rigorously validates the whole of a string to ensure it represents a float.
// Validate a string containing a float value // Does not handle scientific notation, or hex floats (!!) // After all, this is designed for 95% of likely human entered data integer ValidateSimpleFloat(string sin) { sin = llToLower(sin); // Avoid run time fail (for lslEditor at least) if string looks remotely like scientific notation if (llSubStringIndex(sin, "e") != 1) return FALSE; list temp = llParseStringKeepNulls(sin, ["."], [] ); string subs = llList2String(temp, 0); if ( (string) ( (integer) subs) != subs) return FALSE; if ( (temp != []) > 2) return FALSE; if ( (temp != [])== 2) { subs = llList2String(temp, 1); // extract the decimal part // must have no sign after DP, so handle first decimal discretely string first = llGetSubString(subs, 0, 0); if ( (string) ( (integer) first) != first) return FALSE; if ( (string) ( (integer) subs) != subs) return FALSE; } return TRUE; }
Caveats:
 Under LSOLSL 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 LSOLSL 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.
 Due to the limited precision with which floats are stored, not all integer values can be accurately held in a float. Integers above 16,777,216 are rounded down to the nearest even number; above 33,554,432 to the lower multiple of 4 etc.
 "nan" (notanumber), "inf" (infinity) 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 SVC6847

(float)llList2String( llParseStringKeepNulls( llToLower( llStringTrim( vStrDta, STRING_TRIM ) ), ["inf", "nan"], [] ), 0 )

FloattoString
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  (string)float_value Mono 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  0x6487ED5p25  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.
DF 
PR 
ST 