Using a sub-string operator on a string allows a specific portion of the string to be accessed. This portion may be the target of an assignment operation or a reference to a portion of the string. To determine the coordinates of the string portion to be used, count the characters from the beginning to the end of the string, including spaces.
LET <STRVAR$>(<A>:<B>)=<C$>
<C$> = <STRVAR$>(<A>:<B>)
= the position of the first character in the desired string
= the position of the last character in the desired string.
= base string variable
If the A parameter is less than 1, it is automatically assigned a value of 1. Because the string is calculated starting with 1, the A parameter cannot be less than 1.
If B is greater than the length of the string, it is replaced with the length of the string.
If A is greater than B, a NULL string (""), which points to the location of the smaller of A or the end of the string, is returned. This is used when adding a string in the middle of another string without removing a character.
This is an example of a sub-string reference:
LET A$="Zebra Quality Printers" LET B$=A$(1:13) PRINT B$ Zebra Quality
This is an example of a sub-string assignment.
LET A$= "1234" LET A$(2:3)= "55" ! A$ NOW = 1554 LET A$(2:3)= "" ! A$ NOW = 14 LET A$= "1234" LET A$(2:3)= A$(1:2) ! A$ NOW = 1124 LET A$= "1234" LET A$(2:1)= "5" ! A$ NOW = 15234
The best way to think of assignment to a sub-string is as follows: an assignment is like selecting a word, and pasting over the selection with the new string.