On 2017-08-04 00:31, Charles Mills wrote:
Certainly if one is looking to save a cycle or two thenif a(i) >= 0 then sum = sum + a(i); should be if a(i) > 0 then sum = sum + a(i); because adding a(i) to sum when a(i) == 0 is a waste of a cycle or two.
Yes, but in this case it *IS* significant, because the initialization of a PL/I "FIXED (7)" with -1.0 < init-value < 0 will set it to MINUS zero (zero with a D-sign) and by adding zero to this will normalize the value to have a C-sign.
As I already write in the title, the gal or guy who wrote this code is just a trifle too smart for her or his own good, I've been using PL/I for nearly 32 years, and until I used UNSPEC() on "sum", the code didn't make any sense to me.
FWIW, my original post contained a type, if substr(unspec(sum), 25, 8) ^= '0d'bx then should have been if substr(unspec(sum), 29, 4) ^= 'd'bx then or, like in the original code, if substr(unspec(sum), 8*stg(sum)-3, 4) ^= 'd'bx then Mea culpa, too much Intel assembler where hex constants must start with a zero... Robert
-----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Robert Prins Sent: Thursday, August 3, 2017 12:11 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Someone just too smart for his or her own good? Just came across the following, and please don't come back with pedantic remarks about undeclared variables, the code is just to show what's there: dcl sum fixed (7) init (-0.1); for i = 1 to whatever; if a(i) >= 0 then sum = sum + a(i); end; if substr(unspec(sum), 25, 8) ^= '0d'bx then put data(sum); In other words if all a(i) are negative, nothing is printed. A comment in the code suggests that this is faster code, on modern OoO z/OS systems, than the more logical: dcl sum fixed (7) init (-1); for i = 1 to whatever; if a(i) >= 0 then if sum ^= -1 then sum = sum + a(i); else sum = a(i); end; It probably is if the value of whatever is in the order of 42 gazillion, but any other thoughts about this? Robert -- Robert AH Prins robert.ah.pr...@gmail.com Some programming @ <https://prino.neocities.org/zOS/zOS%20Tools.html> ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
-- Robert AH Prins robert(a)prino(d)org ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
