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Left

Returns or replaces a specified number of characters from the left end of a string.

Synopsis

Left(string,length)

Left(string,length)=value

Arguments

string String expression from which the leftmost characters are returned.
length Numeric expression that evaluates to a positive integer indicating how many characters from the beginning of string to return or replace. Fractional numbers are truncated to an integer. If length is 0 or a negative number, Left returns a zero-length string (""). If length is 0 or a negative number, Left performs no replacement. If length is greater than or equal to the number of characters in string, the entire string is returned (or replaced). No padding is performed.
value The value used to replace the specified character(s) at the beginning of string. An expression that evaluates to a string.

Description

The Left function can be used in two ways:

  • To return a substring from the beginning (left end) of string. This uses the Left(string,length) syntax.

  • To replace a substring from the beginning (left end) of string. The replacement substring may be the same length, longer, or shorter than the original substring. This uses the Left(string,length)=value syntax.

Left(string,length) returns the leftmost character(s) of string. The length argument specifies how many characters of string to return. If length is 0 or a negative number, Left returns the empty string (""). If you specify a length greater than the length of string, the entire string is returned.

Left(string,length)=value replaces the leftmost character(s) of string with value. The length argument specifies how many characters of string to replace. If length is 0 or a negative number, string is unchanged. This is true even when string is the empty string (""). If length is greater than the length of string, string is replaced by value.

To determine the number of characters in string, use the Len function.

The Right function returns (or replaces) the specified number of characters from the end (right end) of a string. The Mid function returns (or replaces) the specified number of characters from a specified starting point within a string.

Examples

The following example uses the Left function to return the first three characters of mystr, the first 99 characters (in this case, all of the characters), and the first 0 characters:

Dim mystr
mystr = "InterSystems"
Println "length 3:",Left(mystr,3)   ' Returns "Int"
Println "length 99:",Left(mystr,99) ' Returns "InterSystems"
Println "length 0:",Left(mystr,0)   ' Returns ""
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The following example uses the Left function to replace the first three characters of mystr with a five-character string:

Dim mystr
mystr = "NtrSystems"
PrintLn mystr
Left(mystr,3)="Inter"
PrintLn mystr
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The following example deletes (replaces with the null string) the first three characters of mystr:

Dim mystr
mystr = "NtrSystems"
PrintLn mystr
Left(mystr,3)=""
PrintLn mystr
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The following example replaces all of the characters of mystr, because length is greater than the length of mystr:

Dim mystr
mystr = "Oracle"
PrintLn mystr
Left(mystr,99)="InterSystems"
PrintLn mystr
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The following example shows that length=0 has no effect on mystr:

Dim mystr
Dim empstr
mystr = "InterSystems"
empstr = ""
PrintLn mystr
Left(mystr,0)="Bongo"
PrintLn "string out:",mystr
Left(empstr,0)="BongoSystems"
PrintLn "string out:",empstr
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See Also