Substring Assignment

A value can be assigned to a substring of a string variable, dynamic array or dimensioned array variable using the three assignment statements described below.

Syntax

X[start#,replace#] = expression

X{<attr#{,value#{,subvalue#}}>}{[start#, replace#]} = expression

X(row{,column}) {<attr#{,value#{,subvalue#}}>} {[start#,replace#]} = expression

Comments

The first form of the statement replaces the substring defined by start# (the first character position) and replace# (the number of characters) with the string given by expression.

The second form replaces a substring of dynamic array X with the string given by expression.

The third form replaces a substring of dimensioned array X with the string given by expression.

Note

The discussion and examples in this section concentrate on simple substring assignment. For more information about array assignment, refer to the description of dynamic arrays.

In the statement

X[start#,replace#] = "ABC"

start# and replace# have the following meanings:

start# > 0 The starting position of the substring counting from the left.

start# = 0 Same as the value start# = 1.

start# < 0 The starting character of the substring counting backward from the right. For instance, -1 is the last character of the string, -2 is second to the last, and so on.

replace# > 0 The number of characters to replace in the substring in X, starting with start# and continuing left to right.

replace# = 0 A substring of zero length is replaced in X, meaning that the new string ("ABC" in the example) is inserted, starting at character position start#. If start# >= 0, the new string is inserted to the left of start#. If start# < 0, the new string is inserted to the right of start#. X[1,0]  concatenates a string to the front of X and X[-1,0]  concatenates a string to the end of X.

replace# < 0 The last character of the substring, counting from the right side of the string. If replace# is -1, the substring is replaced, from start# to the end of the string, with the expression on the right-hand-side. This makes it easy to manipulate strings of unknown length.

Examples

If X = "ABCDEFGH", the following substring values are assigned:

X[-5,-3]="vwxyz"

X becomes ABCvwxyzGH by replacing the substring starting five characters from the end of string X and ending three characters from the end.

X[1,0]="999"

X becomes 999ABCDEFGH by concatenating the subvalue 999 to the front of string X.