Those Stupid Quotation Marks!

Hey, Ted:

I am attempting to use QCMDEXC to run Open Query File within an RPG IV program but the compiler generates errors RNF0312 (A right parenthesis is expected but is not found) and RNF5347 (An assignment operator is expected with the EVAL operation). Do you see anything wrong with my code?

--PG

Here's the free-format RPG code PG sent me. (The file and field names have been changed to protect the guilty.)

@qcmdexec('OPNQRYF FILE((MYFILE)) QRYSLT('FLD *EQ %WLDCRD("*AA*")')');

PG is trying to select all records in file MYFILE that have AA anywhere in field FLD. PG's problem is that he (she?) has embedded single quotation marks (or "quotes," as they're often called, or "tick marks," as a former associate of mine referred to them) within single quotation marks. I get lots and lots of complaints about the use of quotes, almost always from people who complain that they don't like CL. But PG's case shows that it's not just CL that suffers from this problem. My email and my experience on the job show that it's not just newbies who don't understand how to use quotes.

To use quotes properly in CL, RPG, and DDS, follow these simple rules.

Rule 1: You must always have an even number of quotes in a character string, including the quotes that delimit the string.

If you have an even number of quotes, you may or may not have a problem. If you have an odd number of quotes, you've definitely got a problem somewhere.

Rule 2: You must place two adjacent quotes inside a string in order to store one quote.

Since the quote character delimits a character literal, IBM had to come up with a special way to indicate that a quote is part of a literal. Look at this:

eval ClubName = 'The Ladies' Red Rubber Ball Society'

How is the RPG compiler to know that the string doesn't stop after the final letter of the second word?

Here's the example I always use. If the message you want to get across is that people should dine at your friend Joseph's food emporium, you might write code like the following:

/* CL */
chgvar  var(&Message)  value('Eat at Joe''s!')

/* RPG IV */
eval Message = 'Eat at Joe''s!'

/* DDS */
A                             2 34'Eat at Joe''s!'

In all these cases, the message is the same: Eat at Joe's!

Rule 3: Some people like to use a one-byte identifier that contains a quote in order to avoid doubled quotes. (Well, it's not really a rule, but it's still useful information.)

/* CL */
dcl  &Quote       *char    1    value('''')
dcl  &Message     *char   80

chgvar var(&Message) +
       value('Eat at Joe' *cat &Quote *cat 's!')

/* RPG IV */

D Quote           c                   const('''')
D Message         s             80a

C                   eval      Message = 'Eat at Joe' +
C                               Quote + 's!'

You don't avoid doubled quotes completely, as the initial value of the Quote constant or variable has four quotes. The outer two delimit the string. The inner two signify one quote. But you don't have to use a doubled quote anywhere else in the program.

Now back to PG's question. All he (she?) has to do is double the embedded single quotes.

@qcmdexec('OPNQRYF FILE((MYFILE)) QRYSLT(''FLD *EQ %WLDCRD("*AA*")'')');

I'm glad PG took the time to write. I see this mistake and many imaginative work-arounds quite often, but it had never occurred to me to write about the "tick-mark" problem in Four Hundred Guru. Thanks.

--Ted