Re: ITER, LEAVE, GOTO - dirty opcodes? was ->RE: NOTO (or "no GOTO i n FreeForm RPG") -- RPG400-L

On Tuesday, February 17, 2004, at 07:57 AM, Bartell, Aaron L. (TC) wrote:

The first IF statement below will check to see if I want to include this record as part of my results. If I don't, it will just get the next record from the ResultSet. I am curious as to how you would code this without using the CONTINUE keyword

I should know better than to enter this discussion but ...

LEAVE and ITER are always conditional operations. That means they can be removed from code by reversing the test. In your example Java code the continue can be removed by:

while (rs.next()) { if (!isNonStoreAccnt(rs.getInt("CORPCONS"), rs.getInt("STORE"))) { if (firstTime == 'Y') { ...code... firstTime = 'N'; } if (rs.getInt("CORPCONS") != savCorpCons) { ...code... } if (rs.getInt("DIV") != savDiv || rs.getInt("SUBDIV") != savSubDiv || rs.getInt("PRDDIV") != savPrdDiv || rs.getInt("PRDSUBDIV") != savPrdSubDiv) { ...code... } } } // End While Loop

The only valid argument in favour of continue (or ITER) in the original construct is that positive tests are easier to grasp than negative tests. !isNonStoreAccnt is a negative test. I would probably solve that by providing an isStoreAccnt method rather than the existing negative method (or create a wrapper method that does the negation).

This is not to say that ITER and LEAVE should never be used, just that they should be avoided. These operations are similar to GOTO. The problem is not the GOTO itself, rather it is the lack of a COME-FROM. GOTO is occasionally useful but like LEAVE and ITER it usually indicates poor structure. And the less said about the LEAVESR abomination the better.

Whenever you find yourself coding LEAVE or ITER have a closer look at the code. In most cases restructuring the existing tests will remove the need for LEAVE or ITER and simplify the code. If not then use them but don't use them as a matter of course. THINK about the code you write.

LEAVE and ITER (and continue and break) make sense particularly when the code is driven by a state machine but even then are more often an indication of a language weakness disguised as a feature (e.g., switch) however use inside I/O loops or conditional tests is usually just laziness.

Regards,
Simon Coulter.
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