Position

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4D v16.3

Position


Position ( find ; aString {; start {; lengthFound}}{; *} ) -> Function result

Parameter	Type	Description
find	String	String to find
aString	String	String in which to search
start	Longint	Position in string where search will start
lengthFound	Longint	Length of string found
*	Operator	If passed: evaluation based on character codes
Function result	Longint	Position of first occurrence

Description

Position returns the position of the first occurrence of find in aString.

If aString does not contain find, it returns a zero (0).

If Position locates an occurrence of find, it returns the position of the first character of the occurrence in aString.

If you ask for the position of an empty string within an empty string, Position returns zero (0).

By default, the search begins at the first character of aString. The optional start parameter can be used to specify the character where the search will begin in aString.

The lengthFound parameter, if passed, returns the length of the string actually found by the search. This parameter is necessary to be able to correctly manage letters that can be written using one or more characters (e.g.: æ and ae, ß and ss, etc.).
Note that when the * parameter is passed (see below), these letters are not considered as equivalent (æ # ae); in this mode, lengthFound is always equal to the length of find (if an occurrence is found).

By default, the command makes global comparisons that take linguistic particularities and letters that may be written with one or more characters (for example æ = ae) into account. On the other hand, it is not diacritical (a=A, a=à and so on) and does not take "ignorable" characters into account (Unicode specification). Ignorable characters include all characters in unicode C0 Control subset (U+0000 to U+001F, ascii character control set) except printable ones (U+0009 TAB, U+0010 LF, U+0011 VT, U+0012 FF and U+0013 CR).
To modify this functioning, pass the asterisk * as the last parameter. In this case, comparisons will be based on character codes. You must pass the * parameter:

If you want to take special characters into account, used for example as delimiters (Char(1), etc.),
If the evaluation of characters must be case sensitive and take accented characters into account (a#A, a#à and so on).
Note that in this mode, the evaluation does not handle variations in the way words are written.

Note: In certain cases, using the * parameter can significantly accelerate the execution of the command.

Warning: You cannot use the @ wildcard character with Position. For example, if you pass "abc@" in find, the command will actually look for "abc@" and not for "abc" plus any character.

Example 1

This example illustrates the use of Position. The results, described in the comments, are assigned to the variable vlResult.

 vlResult:=Position("ll";"Willow") ` vlResult gets 3

 vlResult:=Position(vtText1;vtText2) ` Returns first occurrence of vtText1 in vtText2

 vlResult:=Position("day";"Today is the first day";1) ` vlResult gets 3

 vlResult:=Position("day";"Today is the first day";4) ` vlResult gets 20

 vlResult:=Position("DAY";"Today is the first day";1;*) ` vlResult gets 0

 

 vlResult:=Position("œ";"Bœuf";1;$length) ` vlResult =2, $length = 1

Example 2

In the following example, the lengthFound parameter can be used to search for all the occurrences of "aegis" in a text, regardless of how it is written:

 $start:=1

 Repeat

    vlResult:=Position("aegis";$text;$start;$lengthfound)

    $start:=$start+$lengthfound

 Until(vlResult=0)