char-var = character-expression
where char-var can be a character variable, array element, or substring.
There is one important restriction on character assignment statements: none of
the characters being referenced in the expression on the right may be defined in
char-var on the left, that is to say there can be no overlap. Thus the assignment
statement:
STRING(1:N) = STRING(10:)
is valid only as long as N is no higher than 9. It is, of course, easy to get
around this restriction by using a temporary character variable with a suitable
length.
Note when a value is assigned to a substring (as in the last example) the other characters in the parent string are not affected at all. If the string was previously undefined then the other character positions will still be undefined; otherwise they will retain their previous contents.
The expression and the character object to which its value is assigned may have different lengths: if the expression is longer then the excess characters on the right are lost; if it is shorter then blanks are appended. Care is needed to declare adequate lengths or else the results can be unexpected:
CHARACTER AUTHOR*30, SHORT*5, EXPAND*10 AUTHOR = 'SHAKESPEARE, WILLIAM' SHORT = AUTHOR EXPAND = SHORT |
EXPAND will be 'SHAKE ' where the last five characters are
blanks.
