I also thought: "great explanation" and nodded sagely when I read this.
However, consider this code:
NUL = ''
CM = ','
A = -409071.8775: CM: 475000: CM: -652413: CM: 652413: CM: -475000:
TEST.VMC = 1
TEST.TOTAL = 0
LOOP UNTIL FIELD(A, CM, TEST.VMC) = NUL DO
TEST.TOTAL += FIELD(A, CM, TEST.VMC)
TEST.VMC += 1
IF TEST.TOTAL = 0 THEN
PRINT TEST.TOTAL, (TEST.TOTAL = 0), TEST.TOTAL - 0,
(OCONV(TEST.TOTAL, 'MD0') = 0)
Running this on our Universe system 11.1.1 produces:
0 0 0 1
So, in other words zero is the total result in TEST.TOTAL but this does
not equate to zero.
Now I know I can get round this by rounding the answer but am not sure why
I should have to. Any ideas?
wrote in message
As a general rule in programming, comparison of floating point values
for equality should be avoided. This is because, just as we cannot
write the number one third accurately in decimal notation, so the IEEE
floating point format used by computer systems cannot store numbers
accurately. The example that I use when teaching training courses is
14.2 which actually ends up as something close to 14.19999999997.
UniVerse gets around this with a wonderful concept called "wide zero"
that says, when testing for equality of floating point numbers, they
must be within some specified value of being equal rather than
strictly equal. The default wide zero error tolerance, set in IEEE
format with the WIDEZERO configuration parameter, is 2.91 * 10^-11 (2^
035) which is good for most business applications but occasionally needs
Unidata has a command, SET.WIDEZERO, to serve the same purpose but
defaults to 0.0 for backward comaptibility.
Ladybridge Systems Ltd
17b Coldstream Lane, Hardingstone, Northampton NN4 6DB, England
----- Original Message -----
From: "George Hammerle"
Sent: Thursday, September 29, 2011 1:30 PM
Subject: [U2] The math just doesn't work.
> Can anybody please help?
> For some reason A + B does not equal C in the comparison below. Is
> there any trick to get the comparisons to work properly?
> Unidata 7.2 on Hp Unix 11+
> Top of "TEST.COMP" in "RMH.MAIN", 13 lines, 263 characters.
> *--: P
> 001: A = 3176.79
> 002: B = 106.19
> 003: C = 3282.98
> 004: D = 920.11
> 005: A = A + D
> 006: C = C + D
> 007: IF (A+B) # C THEN
> 008: CRT '(A+B) # C? YOU LIE'
> 009: CRT 'A = ':A:', B = ':B:', (A+B) = ':(A+B):', C = ':C
> 010: END ELSE
> 011: CRT '(A+B) = C? YOU ROCK'
> 012: CRT 'A = ':A:', B = ':B:', (A+B) = ':(A+B):', C = ':C
> 013: END
> *--: FIBR
> Filed "TEST.COMP" in file "RMH.MAIN" unchanged.
> Compiling Unibasic: /db1/ud1/PGM/RMH.MAIN/TEST.COMP in mode 'u'.
> compilation finished
> (A+B) # C? YOU LIE
> A = 4096.9, B = 106.19, (A+B) = 4203.09, C = 4203.09
> George Hammerle
> Programming Dude
> Hubert Company LLC.
> 9555 Dry Fork Road
> Harrison, Ohio 45030
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