Syntax: POS("Needle", "Haystack")
Discussion: The POS function returns the position of one specified string argument within a second string argument. The first string argument ("Needle") is a string value whose position within the second string argument is to be determined. The second string argument ("Haystack") is the string value to be searched for the first string argument.
Both string arguments can be string constants, single-element string variables, or string array elements.
Either the first or the second string argument (but not both) can be a string expression or a string function.
The value returned by the POS function is the position within "Haystack" of the first character of the first occurrence (from left to right) of a substring equal to "Needle". For internal string values, counting begins at character position 1.
If "Needle" does not equal a substring of "Haystack", the POS function returns a value of zero.
The intermediate result of the POS function is stored in an accumulator with a precision of 16.8 If this result is then stored in a receiving numeric variable, its precision is adjusted to the defined precision of that variable.
Example 1: X = POS(A$,B$)
In the above example, the value contained in the string variable A$ is compared to the value stored in B$. If a match is found, the POS function returns the matching position; this value is then stored in the numeric variable X.
For example, if A$ equals "AT" and B$ equals "SIGNATURE", then the POS function will return a value of 5 (the starting position of the string "AT" within the value "SIGNATURE".)
Example 2: VALUE = POS(STR$,"ABCDEF")
In this example, the value of string variable STR$ is compared to the string constant "ABCDEF". If the value of STR$ matches a portion of the constant, its position is returned and stored in the numeric variable VALUE. For example, if STR$ equals "B", the function will return a value of 2 (since "B" is in the second position of the string constant).
Or, if STR$ equals "Z", the function will return a value of zero, since "Z" is not contained in the constant.
Also, if STR$ equals "DE", the function will return a value of 4 (the substring "DE" starts at the fourth position of the constant).
Example 3: N = POS("SMITH",NAME$)
In this example, the string constant "SMITH" is compared to the string variable NAME$. If "SMITH" is located anywhere within NAME$, its position will be returned and stored in the numeric variable N.
Note: If "SMITH" is not found in the variable NAME$, the POS function will return a value of zero. This programming technique can be useful for determining if a particular string value is contained within a specific data field.