Just how much do you know about this handy command?
There, on the cover of
a tabloid, was my life summed up in one sentence: "Inquiring minds want to
know." As I waited to pay for the few grocery items in my hands, the tabloid
mere centimeters from my face, the nagging question roared through my brain,
relentless, biting, unforgiving: "Why is there no From Separator (FROMSEP)
parameter on the Convert Date (CVTDAT) command?" My inquiring mind wanted to
know.
You spend years with a command, getting to know it, watching it do
its job, and just when you think you understand it—bang! —there's
yet another surprise. CVTDAT and I went way back, to my System/38 days. We had
enjoyed a good working relationship. I used it mostly to convert dates between
the MMDDYY format—to which the users were accustomed—and the YYMMDD
and YYYYMMDD formats used in the database files. I would also call upon CVTDAT
to verify that the value of a variable was a valid date. I thought I understood
CVTDAT. God knows I tried.
And then one day, I learned that there is a
very good reason why CVTDAT has no FROMSEP parameter: It doesn't need one. But,
of course, there's more to the story than that. If you find yourself in a
relationship with CVTDAT, here are some things you really should know.
1.
There is no FROMSEP parameter because the value to be converted may be edited or
not. According to the Help text, CVTDAT allows you a choice of separator
characters: period, comma, slash, and hyphen. What the help text doesn't say is
that you may also use a single space character as a separator. Therefore, CVTDAT
lets you express the date January 28, 2000, in any of these ways on a MMDDYY
system:
012800
01.28.00
01,28,00
01/28/00
01-28-00
01
28 00
2. You may omit the leading zeros of the month, day,
and year portions of edited dates. The following are some acceptable ways to
express January 2, 2003, on a system defined to use MMDDYY date
format.
01/02/03
1/2/3
1/2/03
1/02/03
3.
You may use the same five editing characters in the TOSEP parameter that are
acceptable to the DATE parameter. Specify *BLANK in order to separate the
different parts of a date with single spaces. The fact that a blank delimiter is
permitted is documented in the Help text.
4. The TOSEP parameter
does not apply to—and is ignored when converting to—*ISO/*JIS, *USA,
and *EUR formats, for which editing is already defined. *ISO and *JIS are
identical. Both use hyphens to edit in YYYY-MM-DD format. *USA uses the slash to
edit in MM/DD/YYYY format. *EUR uses the period to edit in DD.MM.YYYY
format.
5. Trailing blanks are OK, but leading blanks are a no-no. This
applies to both edited and unedited dates. As long as the date is left-justified
within the variable, CVTDAT does not care how long the variable is.
DCL &FromDate *CHAR 16
DCL &ToDate *CHAR 6
CVTDAT DATE(&FromDate) TOVAR(&ToDate) +
FROMFMT(*YMD) TOFMT(*MDY) TOSEP(*NONE)
If &FromDate has the value 3/6/4 followed by 11 blanks, &ToDate
takes the value 060403. If &ToDate had been defined with a longer length,
the seventh and subsequent bytes would have been filled with blanks.
Thus
I learned that, in addition to converting and verifying dates, CVTDAT can edit
and de-edit them. How much more would you like to know about CVTDAT, Mr. or Ms.
Inquiring Mind? I'll leave it to you to get better
acquainted.
Ted Holt has worked in the
information industry since 1981, primarily with IBM midrange systems. He is the
author of Complete
CL and Power CL, both of
which are available from the MC Store. (He
has aged a few years since that photo was made).
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