Difference between revisions of "LlSubStringIndex"

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(restructure startswith to work like endswith, rather than burning run time to search all the haystack in the often common case of needle not found)
m (clarify to concise & calculates & clever from clear and tests and arcane -- courtesy reasoning by analogy with hex)
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Tests to see if one string contains a copy of another:
Tests to see if one string contains a copy of another:


1. Clear and conventional:
1. Concise & conventional:


<pre>
<pre>
Line 62: Line 62:
Note: Some of the snippets above return a result without ever calling llSubStringIndex.
Note: Some of the snippets above return a result without ever calling llSubStringIndex.


2. Clever and smaller (tests contains in ~54 bytes rather than ~60):
2. Clever & smaller (calculates contains in ~54 bytes rather than ~60):


<pre>
<pre>
Line 71: Line 71:
</pre>
</pre>


Note: The llSubStringIndex function returns -1 only when not found and the ~ operator returns zero only for -1, so the arcane combination ~llSubStringIndex returns zero only for not found, else nonzero for found.
Note: The llSubStringIndex function returns -1 only when not found and the ~ operator returns zero only for -1, so the clever combination ~llSubStringIndex returns zero only for not found, else nonzero for found.


Note: Smaller was not noticeably faster or slower when our [[Code Racer]] and [[Efficiency Tester]] harnesses measured the expression <nowiki>{ contains("wiki.secondlife.com", "wiki"); }</nowiki>.
Note: Smaller was not noticeably faster or slower when our [[Code Racer]] and [[Efficiency Tester]] harnesses measured the expression <nowiki>{ contains("wiki.secondlife.com", "wiki"); }</nowiki>.

Revision as of 22:33, 17 October 2007

Summary

Function: integer llSubStringIndex( string source, string pattern );

Returns an integer that is the index of pattern in source.

• string source
• string pattern

If pattern is not found in source, -1 is returned.
The index of the first character in the string is 0

Caveats

  • Performs a literal match (case sensitive).
    • Wildcards and RegEx are not supported.
  • Attempting to match an empty string ("") will return 0 instead of -1.
All Issues ~ Search JIRA for related Bugs

Examples

Matching against last names: 

default
{
    state_entry()
    {
        llSensorRepeat("", NULL_KEY, AGENT, PI, 96.0, 20);
    }
    
    sensor(integer NumDet)
    {
        integer i;
        
        //Loop through all the sensor data and match against " Linden", 
        //this causes it to match with any last name of Linden (since there can't be spaces before the firstname)
        //Alternatively you could match a firstname with "FirstName "
        for(i = 0; i < NumDet; ++i)
            if(~llSubStringIndex(llDetectedName(i), " Linden"))
                llInstantMessage(llDetectedKey(i), "Hello, I see you!");
    }
}

Useful Snippets

Tests to see if one string contains a copy of another:

1. Concise & conventional: 

integer contains(string haystack, string needle) // http://wiki.secondlife.com/wiki/llSubStringIndex
{
    return 0 <= llSubStringIndex(haystack, needle);
}

integer startswith(string haystack, string needle) // http://wiki.secondlife.com/wiki/llSubStringIndex
{
	return llGetSubString(haystack, 0, llStringLength(needle) - 1) == needle;
}

integer endswith(string haystack, string needle) // http://wiki.secondlife.com/wiki/llSubStringIndex
{
	return llGetSubString(haystack, -llStringLength(needle), -1) == needle;
}

Note: Some of the snippets above return a result without ever calling llSubStringIndex.

2. Clever & smaller (calculates contains in ~54 bytes rather than ~60): 

integer contains(string haystack, string needle) // http://wiki.secondlife.com/wiki/llSubStringIndex
{
    return ~llSubStringIndex(haystack, needle);
}

Note: The llSubStringIndex function returns -1 only when not found and the ~ operator returns zero only for -1, so the clever combination ~llSubStringIndex returns zero only for not found, else nonzero for found.

Note: Smaller was not noticeably faster or slower when our Code Racer and Efficiency Tester harnesses measured the expression { contains("wiki.secondlife.com", "wiki"); }.

See Also

Functions

•  llListFindList – Find a list in another list
•  llGetSubString – Copy out part of a string of characters

Deep Notes

Search JIRA for related Issues

Signature

function integer llSubStringIndex( string source, string pattern );
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