Category:LSL String

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Revision as of 09:10, 10 January 2013 by Omei Qunhua (talk | contribs) (Comment on UTF-16 space requirements. Correct llSay truncation limit (1024 characters, not 1023 bytes). (Tested 10-Jan-13). Comment on concatenation and global definitions.)
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See also Text.

A string is text data.

String values are enclosed in double quotes when defined in LSL text.

Any character may be used in a string though some will need to be escaped (see the Escape Codes section on this page for more info.)

The length of a string is only limited by available script memory. (see the String Length Restraints section on this page for some operational restraints.) But note that in Mono, strings use UTF-16 and occupy two memory bytes per character.

Strings can be concatenated (joined together) using the + operator. Note that concatenation cannot be done when defining a string as a global variable, as + is treated as an executable instruction, it's not handled by the compiler. Concatenation can only be done within executable code, i.e. inside a user defined function or in an event.

Some string operations can be done via built-in functions, such as those that can make text all upper and lower case. Other operations, such as replace, left, right, wrap, etc, must be done via functions invented by other LSL users (examples of which are at the bottom of this page.)

You have no control over the font face, size, weight or colour that string output is displayed in on user screens or on menus. The look of text that displays on screens, such as chat from a text, is controlled by users (though not many change the defaults.) You can only control whether the text is lower or upper case.

(The only time you have control over the colour of displayed text is when it is Floating Text.)


String examples: <lsl>"Hello Avatar!" "Yes" "No" "It's 10 o'clock." "I am 21 years old!" "Help " + "me" EOF

//The following two strings have the same value (i.e. they will both produce text with line breaks in it.)

"I scream,\nyou scream,\nwe all scream,\nfor ice-cream!" "I scream, you scream, we all scream, for ice-cream!" </lsl>


Variable: string name;

<lsl>string name;</lsl> Declares a variable of type string named name, with the value ""

• variable name – variable name

Variable: string name = value;

<lsl>string name = value;</lsl> Declares a variable of type string named name, with the value value.

• variable name – variable name
• expression value – string expression or constant

Typecast: (string)value

<lsl>(string)value</lsl> Converts value to a value of type string.

• expression value – expression or constant

Operators

See Operators for more information.

Combine: value1 + value2

<lsl>(value1 + value2)</lsl> Combines two strings into a single string without modifying the inputs. Appends value2 to value1 and returns the resulting string.

• expression value1 – string expression or constant
• expression value2 – string expression or constant

Comparison: value1 == value2

<lsl>(value1 == value2)</lsl> Compares two strings, returns one if same length and same characters, else returns zero. This operator works exactly like !strcmp(value1, value2) in C, thus technically differs from the counterintuitive behavior of the == operator in C and in Java.

• expression value1 – string expression or constant
• expression value2 – string expression or constant

Comparison: value1 != value2

<lsl>(value1 != value2)</lsl> Compares two strings, returns zero if same length and same characters, otherwise non-zero. This operator works exactly like strcmp(value1, value2) in C, thus technically differs from the counterintuitive behavior of the != operator in C and in Java.

• expression value1 – string expression or constant
• expression value2 – string expression or constant

Escape Codes

Substring Replaced with
\t four spaces
\n new line
\" double quote
\\ backslash

Escape codes are translated when the script is compiled; not while it's running. The compiler will ignore any other combination of \ with a character by removing the \. So "\a" means "a". The result is that only strings that are inside your script when it is compiled will get, say, \n turned into a "new line" character. Text you read in from a notecard, chat, http, object name or description, etc, will not be checked for escape codes -- that same \n typed in a notecard doesn't automatically turn into a "new line" character. You'll have to do that yourself, if you really really need it for some reason.

Those who are coming to LSL from such languages as C and Java may find these LSL string escape rules confusing at first. In LSL, "\n" means llUnescapeURL("%0A"), as it does in C and Java, but "\t" means llUnescapeURL("%20%20%20%20") rather than llUnescapeURL("%09"). Additionally there is no "\r" escape code and "\r" will translate to "r" rather than llUnescapeURL("%0D").

For runtime translation of escaped characters try the user function Unescape.

Characters with Accents

It used to be that your script would not compile if you included in it a string containing a character with an accent, such as "écoutez", or punctuation not used in English, such as "¿Entiende?".

Sometime in late spring / early summer 2008, scripts began compiling with accents in text strings.

That is to say:

<lsl>string hello = "Avatar écoutez";</lsl>

String Length Restraints

As noted at the start of this page, the length of a single string is only limited by available script memory. However, there are some operational limitations. Many Communications functions and some other functions also impose limits on input strings. Those limits may result in error messages at runtime or "silent" truncation (i.e. you get no error notice, nor any indication that it has been done.).

Examples

  • llSay - When using llSay, any text string being said will be truncated to 1024 CHARACTERS, both under LSO and Mono. (That's 2048 bytes of memory space in Mono (UTF-16) ).
  • llGetNotecardLine - When reading in lines from notecards, lines longer than 255 characters will be truncated silently.
  • llDialog - If the message or button texts are too long a non-fatal error is produced when the function is called.

Notes
Limits of this type are always documented, an absence of limits in the documentation means there are no known limits (that are outside the norm for the language).

Trimming a String

Trimming a string used to require user-created functions, such as those created for the purpose in Strife Onizuka's library.

Now, however, there is a native LSL function, llStringTrim, which can be used to remove leading and/or trailing spaces. Note though that it does not remove excess spaces that a user may have entered in the middle of a sentence or string, nor is there any other native LSL function which does.

The following code will remove both all double spaces inside a string, as well as any leading and trailing spaces; it will how ever require a substantial amount of memory overhead.

<lsl>string myTrimmedText = llDumpList2String(llParseString2List(src, [" "], []), " ");</lsl>

When accepting user text input from chat, a notecard, or a prim name or description, or any other "free-wheeling" source, it's a good idea to always llStringTrim first before beginning to work with it.

Examples

<lsl>integer int = 48934; string str = (string)int; string str_2; str_2 = str;</lsl>

Useful Functions

User-created utility functions

These functions have been created and contributed by LSL users to perform operations not covered by built-in LSL functions.

function purpose
Chr Returns the Unicode character with the given code. See also Ord.
Float2String Allows string output of a float in a tidy text format, with optional rounding.
Left Returns text left of a specified separator.
Like See if one word matches part of another.
Ord Returns the ordinal (Unicode code) of a character. See also Chr.
RandomString Creates a random string.
RemoveHTMLTags Removes HTML tags from a string ( and newline characters )
Right Returns text right of a specified separator.
str_replace replace all instances of a string with another string in a target string.
Stristr Returns a string from the first occurrence of needle to the end of haystack.
SplitLine Insert 'new line' escape codes at certain positions of a string.
WrapText Break text into line lengths of your specification.

Text-Related Items from the Script Library

Name Creator Description
ParseString2List Strife Onizuka Same as llParseString2List and llParseStringKeepNulls, but not limited to 8 spacers or separators. Thus substitute a call to the llParseString2List and llParseStringKeepNulls functions by a call to ParseString2List whenever you have more than 8 separators or more than 8 spacers.
String Compare Xaviar Czervik Compares two strings and reliably returns either 1, -1, or 0 if they are the same.
XyText Xylor Baysklef Display text (up to 10 characters) on a prim. Use as many prims as desired.
XyyyyzText Criz Collins Display text (up to 10 characters) on a prim. Displays different text for each line instead of one single text, that will be broken into the next lines. Watch here for what that means: http://screencast.com/t/1wMLujLcEO
XyzzyText Thraxis Epsilon and Gigs Taggart Display text (up to 10 characters) on a prim. Way more efficient than XyText.

Subcategories

This category has the following 2 subcategories, out of 2 total.

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