Category talk:LSL Vector

<lsl> //******************************* //IMPOSSIBLE TO GET A ZERO_VECTOR //*******************************

vector c = <0.0, 0.0, 0.1>;

default {

   touch_start(integer total_number)
   {
       c -= <0.0, 0.0, 0.025>;
       llSay(0, (string)c);
       if (c == ZERO_VECTOR) llSay(0, "ZERO_VECTOR"); // never c is a ZERO_VECTOR
   }

} </lsl> <lsl> //********************** //IN THIS WAY IT RUNS... //**********************

vector c = <0.0, 0.0, 0.1>;

default {

   touch_start(integer total_number)
   {
       c -= <0.0, 0.0, 0.025>;
       llSay(0, (string)c);
       if ((string)c == "<0.00000, 0.00000, 0.00000>") llSay(0, "ZERO_VECTOR");
   }

} </lsl> —The preceding unsigned comment was added on 06:29, 29 April 2012 by Zohan Galewind

---

The above is caused by how floating point math works. 0.1 does not fall on an exact boundary as a float, nor does 0.025. Furthermore the rounding on the two values do not exactly line up, so (4 * 0.025) != 0.1. This is not a bug but a caveat of using floating point math. -- Strife ^{(talk|contribs)} 11:00, 29 April 2012 (PDT)

Useful Snippets

The IsVector function fails for vectors whose z element is negative, at least under Mono. (It also does not work on other grids because the cast to vector and back to string eliminates negative zero there.)

I tried the following:

<lsl> // After the "->" is the expected result (for the proposed new function), after the ":" the actual one llOwnerSay( "IsVector(<0.47,0.149, 1.001>) -> 1: " + (string)IsVector( "<0.47,0.149, 1.001>" ) ); llOwnerSay( "IsVector(<0.47,0.149, 1.001,3>) -> 0: " + (string)IsVector( "<0.47,0.149, 1.001,3>" ) ); llOwnerSay( "IsVector(<0.47,0.149,-1.001>) -> 1: " + (string)IsVector( "<0.47,0.149,-1.001>" ) ); llOwnerSay( "IsVector(<0.47,0.149,+1.001>) -> 1: " + (string)IsVector( "<0.47,0.149,+1.001>" ) ); llOwnerSay( "IsVector( < 0.47, 0.149, -1.001 > ) -> 0: " + (string)IsVector( " < 0.47, 0.149, -1.001 > " ) ); llOwnerSay( "IsVector(<0.47,0.1A9,-1.001>) -> 0: " + (string)IsVector( "<0.47,0.1A9,-1.001>" ) ); llOwnerSay( "IsVector(<0.47,;0.149,-1.001>) -> 0: " + (string)IsVector( "<0.47,;0.149,-1.001>" ) ); llOwnerSay( "IsVector(<0.47,0.149,-1.001) -> 1: " + (string)IsVector( "<0.47,0.149,-1.001" ) ); llOwnerSay( "IsVector(<0,0.000,0>) -> 1: " + (string)IsVector( "<0,0.000,0>" ) ); llOwnerSay( "IsVector(<0,0.000,0,0>) -> 0: " + (string)IsVector( "<0,0.000,0,0>" ) ); llOwnerSay( "IsVector(<+0,-0.000,-0>) -> 1: " + (string)IsVector( "<+0,-0.000,-0>" ) ); </lsl>

I propose the following change:

<lsl> // Returns whether the given string contains a vector. // Accepts what the compiler accepts and checks ZERO_VECTOR separately. integer IsVector ( string s ) {

   list split = llParseString2List( s, ["<", ">", ",", " ", "-", "+"], [] );  // not allowed to be inside numbers
   if ( llGetListLength( split ) != 3 ) return FALSE;  // must be 3 elements
   if ( (vector)s != ZERO_VECTOR ) return TRUE;  // parsing error or real ZERO_VECTOR lead to ZERO_VECTOR
   split = llParseString2List( (string)split, ["0", "."], [] );
   return (split == []);

} </lsl>

With this function, the above tests work. It tests for number of elements and then lets the compiler decide what it accepts as vector. Only for ZERO_VECTOR, special treatment is necessary. Therefore, it checks that only zeros and decimal points are in the remaining string. The compiler itself accepts missing ">" and it would also accept more than 3 elements - that's why the function checks the number of elements before.

It's probably not the most efficient way to do it and also accepts more than is actually valid (esp. for ZERO_VECTOR), but it does accept all valid vectors (I hope ^^). Discussion and improvements are welcome. For IsRotation, the implementation would be almost the same, except checking for 4 elements instead of 3.

Shuichi Shinji 01:13, 31 March 2014 (PDT)

It's going to give false positives on things with multiple periods. And it doesn't handle zero vectors expressed in hex or scientific notation. I applaud your efforts thus far. -- Strife ^{(talk|contribs)} 13:16, 31 March 2014 (PDT)

<lsl> llOwnerSay( "IsVector(<.,.,.>) -> 0: " + (string)IsVector( "<.,.,.>" ) );//BTW: breaks LSL Editor llOwnerSay( "IsVector(<.......,0,0>) -> 0: " + (string)IsVector( "<.......,0,0>" ) );//BTW: breaks LSL Editor llOwnerSay( "IsVector(<0x0.0,0x0p+1,-0x0p-1>) -> 1: " + (string)IsVector( "<0x0.0,0x0.p+1,-0x0.p-1>" ) ); llOwnerSay( "IsVector(<0.0e1,0.0e+1,-0.0e-1>) -> 1: " + (string)IsVector( "<0.0e1,0.0e+1,-0.0e-1>" ) ); </lsl>

Right. I don't know how bad false positives are; the other 2 could be solved by adding 1,x,e,p to the split list, but also adding more false positives, which is not nice. But just adding a "-" to the split list in the original implementation would solve that it's not working for negative z's yet. Of course, it would also add some false positives, such as "1.2--3", but so it already did with "1.2 3" (spaces inside the number) - maybe one line from my proposal could be added so that it properly checks non-ZERO_VECTORs, at least. -- Shuichi Shinji 08:30, 4 April 2014 (PDT)

<lsl> integer IsVector(string s) {

   list split = llParseString2List(s, [" ", "-"], ["<", ">", ","]);
   if(llGetListLength(split) != 7)//we must check the list length, or the next test won't work properly.
       return FALSE;
   if((vector)s != ZERO_VECTOR)//parsing error or real ZERO_VECTOR lead to ZERO_VECTOR
       return TRUE;
   return !((string)((vector)s) == (string)((vector)((string)llListInsertList(split, ["-"], 5))));
   //it works by trying to flip the sign on the Z element of the vector,
   //if it works or breaks the vector then the values won't match.
   //if the vector was already broken then the sign flip will have no affect and the values will match
   //we cast back to string so we can catch negative zero which allows for support of ZERO_VECTOR

} </lsl>