There is one thing which I don't understand about reference modification in Cobol.
The example goes like this:
MOVE VARIABLE(VARIABLE2 +4:2) TO VARIABLE3
Now I do not qutie understand what the "+4:2" references to. Does it mean that the first two signs 4 signs after the target are moved? Meaning if for example VARIABLE (the 1st) is filled with "123456789" and VARIABLE2 contains the 2nd and 3rd position within that variable (so"23"), the target is "23 +4" meaning "789". Then the first two positions in the target (indicated by the ":2") are moved to VARIABLE3. So in the end VARIABLE3 would contain "78".
Am I understanding this right or am I making a false assumption about that instruction?
(VARIABLE2 +4:2) is a syntax error, because the starting position must be an arithmetic expression. There must be a space after the + for this reference modification to be valid. And, VARIABLE2 must be numeric and the expression shall evaluate to an integer.
Once corrected, then 4 is added to the content of VARIABLE2. That is the left-most (or starting position) within VARIABLE1 for the move. 2 characters are moved to VARIABLE3. If VARIABLE3 is longer than two characters, the remaining positions are filled with spaces.
From the 2002 COBOL standard:
8.7.1 Arithmetic operators
There are five binary arithmetic operators and two unary arithmetic operators that may be used in arithmetic expressions. They are represented by specific COBOL characters that shall be preceded by a space and followed by a space except that no space is required between a left parenthesis and a unary operator or between a unary operator and a left parenthesis.
Emphasis added.