I have trouble with WordMat, when calculating with Maxima, which didn't occur before, but started recently. When i calculate something that either results in x00000 or 0,0000x i get the result returned as its scientific expression, IE x*10^5 or x*10^-5. Even though this is correct, i would rather have it returned as a full number.
This only tends to happen when the number of 0's goes beyonda certain number, in the case of decimal numbers its from xe-5 and higher numbers its from xe9 and beyond. I can not turn this off in the settings as far as i can see, but it seems to be a setting in maxima simplification, with the variable option "expon" from what i found here:
file:///C:/Program%20Files%20(x86)/WordMat/Maxima-5.45.1/share/maxima/5.45.1/doc/html/maxima_46.html
Does anyone know of a way to either change the setting in wordmat, or edit the simplification rules in maxima?
I tried:
Turning on and off most setting in wordmat
Restarting my pc
Reinstalling WordMat
Looking through the manual for maxima/wordmat and looking for changeable settings
When you want to control the printed format of numbers, I think the best general answer is to use printf to specify exactly how to print the numbers. For what you want, printf(true, "~f", x) will print the value of x without ever introducing exponential format.
(The default maxima output is basically "~g" which basically automatically chooses between "~f" and "~e" depending on the value of x).
Perhaps a future version of maxima will allow you to change the default output range, but in general printf is the method to use if you want fine-grained control of the output.
Related
Why such code is used in some applications instead of a MOVE?
add 16 to ZERO giving SOME-RESULT
I spotted this in professionally written code at several spots.
Sorce is on this page
Why such code is used in some applications instead of a MOVE?
add 16 to ZERO giving SOME-RESULT
Without seeing more of the code, it appears that it could be a translation of IBM Assembler to COBOL. In particular, the ZAP (Zero and Add Packed) instruction may be literally translated to the above instruction, particularly if SOME-RESULT is COMP-3. Thus, someone checking the translation could see that the ZAP instruction was faithfully translated.
Or, it could be an assembler programmer's idea of a joke.
Having seen the code, I also note the use of
subtract some-data-item from some-data-item
which is used instead of
move zero to some-data-item
This is consistent with operations used with packed decimal fields in IBM Assembly, where there are no other instructions to accomplish "flexible" moves. By flexible, I mean that the packed decimal instructions contain a length field so that specific size MVC instructions need not be used.
This particular style, being unusual, may be related to catching copyright violations.
From my experience, I'm pretty sure I know the reason why the programmer would have done this. It has something to do with the binary representation of the number.
I bet SOME-RESULT is a packed-decimal (or COMP-3) format number. Let's assume the field is defined like this
05 SOME-RESULT PIC S9(5) COMP-3.
This results in a 3-byte field with a hex representation like this
x'00016C'
The decimal number is encoded as a binary encoded decimal (BCD, one decimal digit per half-byte), and the last half-byte holds the sign.
Let's take a look at how the sign is defined:
if it is one of x'C', x'A', x'F', x'E' (café), then the number is positive
if it is one of x'B', x'D', then the number is negative
any of x'0'..'x'9' are not valid signs, so we can distinguish signed packed-decimals from unsigned.
However, a zoned number (PIC 9(5) DISPLAY) - as in the source code - looks like this:
x'F0F0F0F1F6'
As you can see, each decimal digit is an EBCDIC character with the 'zone' part (the first half-byte) always being x'F'.
Now we get closer to your question!
What happens when we use
MOVE 16 TO SOME-RESULT
If you just MOVE a number to such a field, this results in being compiled into a PACK instruction on the machine code level.
PACK SOME-RESULT,=C'16'
A pack instruction takes a zoned number and packs it by picking only the second half-byte of each byte and storing it in the half-bytes of the packed number - with one exception! When it comes to the last byte, it simply flips the two half-bytes and stores them in the last half-byte of the decimal.
This means that the zone of the last byte of the zoned decimal becomes the sign in the packed decimal:
x'00016F'
So now we have an x'F' as the sign – which is a valid positive sign.
However, what happens if use this Cobol instruction instead
ADD 16 TO ZERO GIVING SOME-RESULT
This compiles into multiple machine level instructions
PACK SOME_RESULT,=C'0'
PACK TEMP,=C'16'
AP SOME_RESULT,TEMP
(or similar - the key point is that is needs an AP somewhere)
This makes a slight difference in the result, because the AP (add packed) instruction always sets the resulting sign to either x'C' for a positive or x'D' for a negative result.
So the difference lies in the sign
x'00016C'
Finally, the question is why would one make this difference? After all, both x'F' and x'C' are valid positive signs. So why care?
There is one situation when this slight difference can cause big problems: When the packed decimal is part of an index key, then we would not get a match, even though the numbers are semantically identical!
Because this situation occurred quite often in older databases like VSAM and DL/I (later: IMS/DB), it became good practice to "normalize" packed decimals if they were part of an index key.
However, some programmers adopted the practice without knowing why, so you may come across code that uses this "normalization" even though the data are not used for index keys.
You might also wonder why a compiler does not optimize out the ADD 16 TO ZERO. I'm pretty sure it once did, but that broke a lot of applications, so this specific optimization was removed again or at least made a non-default option with warnings.
Additional useful info
Note that at least the Enterprise Cobol for z/OS compiler allows you to see exactly the machine code that is produced from your source code if use the LIST compile option (see this example output). I recommend to always compile with options LIST, MAP, OFFSET, XREF because these options enable you find the exact problem in your Cobol source even when you only have a program dump from an abend.
Anyway, good programming practice is not to care about the compiler or the machine code, but about the other programmers who will have to maintain, and thus read and understand the code. Good practice would be to always prefer simple and readable instructions, and to document the reasons (right in the code) when deviating from this rule.
Some programmers like to do things "just because they can". I have a feeling that is what you are seeing here. It makes about as much sense as doing
a := 0 + b
would in go.
I'd like to use part to handle expressions of different length but have not been able to find anything in the documentation that addresses how to determine the number of parts of an expression.
I do have an upper bound for the number of parts so, in this particular case, I could loop over the terms until I get an error; however, I was wondering if there is a more direct method?
I can't believe this, but it appears length does the trick.
I assumed it was limited to lists because it returns an error for single numbers, because they are atoms. Apparently my brain decided "doesn't work with atoms" to mean "only work with lists."
However, this does mean that neither part nor length will work if the expression only has one part, so that case has to be handled separately.
I would still be interested in knowing if there is a solution that will work in all cases, so I won't mark this as the answer, just yet.
I am trying to "highlight" references to law statutes in some text I'm displaying. These references are of the form <number>-<number>-<number>(char)(char), where:
"number" may be whole numbers 18 or decimal numbers 12.5;
the parenthetical terms are entirely optional: zero or one or more;
if a parenthetical term does exist, there may or may not be a space between the last number and the first parenthesis, as in 18-1.3-401(8)(g) or 18-3-402 (2).
I am using the regex
((\d+(\.\d+)*-){2}(\d+(\.\d+)*))( ?(\([0-9a-zA-Z]+\))*)
to find the ranges of these strings and then highlight them in my text. This expression works perfectly, 100% of the time, in all of the cases I've tried (dozens), in BBEdit, and on regex101.com and regexr.com.
However, when I use that exact same expression in my code, on iOS 12.2, it is extremely hit-or-miss as to whether a string matching the regex is actually found. So hit-or-miss, in fact, that a string of the exact same form of two other matches in a specific bit of text is NOT found. E.g., in this one paragraph I have, there are five instances of xxx-x-xxx; the first and the last are matched, but the middle three are not matched. This makes no sense to me.
I'm using the String method func range(of:options:range:locale:) with options of .regularExpression (and nil locale) to do the matching. I see that iOS uses ICU-compatible regexes, whereas these other tools use PCRE (I think). But, from what I can tell, my expression should be compatible and valid for my case with the ICU parsing. But, something is definitely different, and I cannot figure out what it is.
Anyone? (I'm going to give NSRegularExpression a go and see if it behaves differently, but I'd still like to figure out what's going on here.)
I have problem with comparison of two variables of "Real" type. One is a result of mathematical operation, stored in a dataset, second one is a value of an edit field in a form, converted by StrToFloat and stored to "Real" variable. The problem is this:
As you can see, the program is trying to tell me, that 121,97 is not equal to 121,97... I have read
this topic, and I am not copletely sure, that it is the same problem. If it was, wouldn't be both the numbers stored in the variables as an exactly same closest representable number, which for 121.97 is 121.96999 99999 99998 86313 16227 83839 70260 62011 71875 ?
Now let's say that they are not stored as the same closest representable number. How do I find how exactly are they stored? When I look in the "CPU" debugging window, I am completely lost. I see the adresses, where those values should be, but nothing even similar to some binary, hexadecimal or whatever representation of the actual number... I admit, that advanced debugging is unknown universe to me...
Edit:
those two values really are slightly different.
OK, I don't need to understand everything. Although I am not dealing with money, there will be maximum 3 decimal places, so "currency" is the way out
BTW: The calculation is:
DATA[i].Meta.UnUsedAmount := DATA[i].AMOUNT - ObjQuery.FieldByName('USED').AsFloat;
In this case it is 3695 - 3573.03
For reasons unknown, you cannot view a float value (single/double or real48) as hexadecimal in the watch list.
However, you can still view the hexadecimal representation by viewing it as a memory dump.
Here's how:
Add the variable to the watch list.
Right click on the watch -> Edit Watch...
View it as memory dump
Now you can compare the two values in the debugger.
Never use floats for monetary amounts
You do know of course that you should not use floats to count money.
You'll get into all sorts of trouble with rounding and comparisons will not work the way you want them too.
If you want to work with money use the currency type instead. It does not have these problems, supports 4 decimal places and can be compared using the = operator with no rounding issues.
In your database you use the money or currency datatype.
Studying for a test right now and can't seem to wrap my head around when to use "V" for a decimal instead of an actual decimal in PIC clauses. I've done some research but can't find anything I understand. Only been learning cobol for about a week, so is there like a rule of thumb here? Thanks for your time.
You use an actual decimal-point when you want to "output" a value which has decimal places, like a report line, a position on a screen, an item in an output file which is going to a "different" system which doesn't understand the format with an implied decimal pace.
That's what the V is, it is an implied decimal place. It tells the compiler where to align results from calculations, MOVEs, whatever. Computer chips, and the machine instructions they support, don't know about actual decimal points for their internal processing.
COBOL is a language with fixed-length fields. The machine instructions don't need to know where the decimal point is (effectively it can deal with everything as integer values) but the compiler does, and the compiler has to do the correct scaling and alignment of results.
Storing on your own files, use V, the implied decimal place.
For data which is to be "human readable" or read by a system which cannot understand your character set, cannot scale what looks like an integer, use an actual decimal-point, . (for computer-readable stuff, you can sometimes use a separate scaling factor, if that is more convenient for the receiving system).
Basically, V for internal, . for external, should be a rule of thumb to get you there.
Which COBOL are you using? I'm surprised it is not covered in your documentation.