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Active Forums => QB64 Discussion => Topic started by: Jaze on November 01, 2021, 03:58:25 pm

Title: Trouble understanding MID$( )
Post by: Jaze on November 01, 2021, 03:58:25 pm
Code: QB64: [Select]
  1. startTime = 34
  2. endTime = 42
  3. lineToPrint$ = "|                                 9:30 AM N-the lobby between 10:13 AM-N   |"
  4.  
  5.  timeString$ = MID$(lineToPrint$, startTime, endTime)
  6.  
the result I get for timeString$ is " 9:30 AM N-the lobby between 10:13 AM-N   "

wtf?

am I missing something? I've had lots of problems with MID$(), especially with INSTR(). MID$() often requires me to fudge the numbers but still works consistently after doing so. Any suggestions?
Title: Re: Trouble understanding MID$( )
Post by: FellippeHeitor on November 01, 2021, 04:12:37 pm
It looks like a matter of adjusting expectations. What did you expect to happen?
Title: Re: Trouble understanding MID$( )
Post by: SMcNeill on November 01, 2021, 04:20:40 pm
Code: QB64: [Select]
  1. startTime = 34
  2. endTime = 42
  3. lineToPrint$ = "123456789012345678901234567890123423456789012345678901234567890123456789012"
  4. lineToPrint$ = "|                                 9:30 AM N-the lobby between 10:13 AM-N   |"
  5.  
  6.  timeString$ = MID$(lineToPrint$, startTime, endTime)
  7.  

Looks to me like things line up proper.  The 34th character is the space before 9, and 42 characters (including it) gives you the rest of the text.  What's wrong with the output?

Are you looking for endTime to be 42-34, or only 8 characters total?
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 01, 2021, 04:25:29 pm
Perhaps you want this:
Code: QB64: [Select]
  1. startTime = 34
  2. endTime = 42
  3. lineToPrint$ = "|                                 9:30 AM N-the lobby between 10:13 AM-N   |"
  4.  
  5. timeString$ = Mid$(lineToPrint$, startTime, 8)
  6. Print timeString$
  7.  
  8.  
  9.  

Mid$(string$, startPosition, ForLengthOf)
Title: Re: Trouble understanding MID$( )
Post by: Jaze on November 01, 2021, 04:29:22 pm
I've had so many bugs with MID$ that I probably didn't check the numbers this time. anyway, I wrote my own just now. duh!
Title: Re: Trouble understanding MID$( )
Post by: Jaze on November 01, 2021, 04:38:18 pm
no. I had it correct. All I did was change "MID$" to the function I wrote "Middle$" and the exact same code functioned the way I intended. Thankfully I haven't had any difficulty with LEFT$ or RIGHT$ or I wouldn't have been able to write the function. Thanks anyway
Title: Re: Trouble understanding MID$( )
Post by: FellippeHeitor on November 01, 2021, 06:08:44 pm
Aaaaand we never learned what he intended to do after all.

Bottom line: MID$ not buggy.
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 01, 2021, 06:23:52 pm
I'll bet real money he intended this:
Code: QB64: [Select]
  1. startTime = 34
  2. endTime = 42
  3. lineToPrint$ = "|                                 9:30 AM N-the lobby between 10:13 AM-N   |"
  4.  
  5. timeString$ = Middle$(lineToPrint$, startTime, endTime)
  6. Print timeString$
  7.  
  8. Function Middle$ (S$, Start_Position&, End_Position&)
  9.     Middle$ = Mid$(S$, Start_Position&, End_Position& - Start_Position&)
  11.  
  12.  
  13.  

It's very logical for a noobie to think like that.
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 01, 2021, 06:29:46 pm
But how'd he do it with Left$ and Right$?
Title: Re: Trouble understanding MID$( )
Post by: SMcNeill on November 01, 2021, 07:18:18 pm
Quote from: bplus on November 01, 2021, 06:29:46 pm
But how'd he do it with Left$ and Right$?

Like so:

Code: QB64: [Select]
  1. startTime = 34
  2. endTime = 42 - startTime
  3. lineToPrint$ = "|                                 9:30 AM N-the lobby between 10:13 AM-N   |"
  4.  
  5. timeString$ = Mid$(lineToPrint$, startTime, endTime)
  6.  
  7. Print Middle$(lineToPrint$, 34, 42)
  8. Print timeString$
  9.  
  10. Function Middle$ (text$, start, finish)
  11.     m$ = Left$(text$, finish - 1)
  12.     m$ = Right$(m$, finish - start)
  13.     Middle$ = m$
  15.  

Note the -1 is my interpretation that he wants to end AT that position and not actually include it.  If I'm wrong, remove that shift.
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 01, 2021, 07:32:25 pm
Yeah the -1 is picked up in the next use of finish.
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 01, 2021, 08:22:29 pm
You know I was looking at this and looking at 34 and 42 and then looking at this and... WTH?
Code: QB64: [Select]
  1. lineToPrint$ = "123456789012345678901234567890123423456789012345678901234567890123456789012"
  2. lineToPrint$ = "|                                 9:30 AM N-the lobby between 10:13 AM-N   |"
  3.  


Oh! you started recounting at 34! Here's a real character ruler:
Code: QB64: [Select]
  1. 'lineToPrint$ = "123456789012345678901234567890123423456789012345678901234567890123456789012"
  2. 'lineToPrint$ = "|                                 9:30 AM N-the lobby between 10:13 AM-N   |"
  3. 'lineToPrint$ = "123456789012345678901234567890123456789012345678901234567890123456789012"
  4. 'lineToPrint$ = "         1         2         3   ^     4 ^       5         6
  5.  
Title: Re: Trouble understanding MID$( )
Post by: Pete on November 02, 2021, 12:09:20 am
Not only is MID$ not buggy, it is also very forgiving. This does not apply to the example posted, but it's worth mentioning other languages will error out if the range given is not within the length of the string. I just thought I'd parse that along.

I was also wondering if the OP was thinking the third argument would cut the string at the 42nd character, instead of include 42 characters following the value of the second argument, 34. I mean if he was looking of a result of: _930 AM he needed to subtract the start time from the end time as in: timeString$ = Mid$(lineToPrint$, startTime, endTime - startTime)

Pete
Title: Re: Trouble understanding MID$( )
Post by: SMcNeill on November 02, 2021, 12:21:30 am
Quote from: bplus on November 01, 2021, 08:22:29 pm
You know I was looking at this and looking at 34 and 42 and then looking at this and... WTH?
Code: QB64: [Select]
  1. lineToPrint$ = "1234567890123456789012345678901234"
  2. lineToPrint$ = "                                 123456789012345678901234567890123456789012"
  3. lineToPrint$ = "|                                 9:30 AM N-the lobby between 10:13 AM-N   |"
  4.  


Oh! you started recounting at 34!

Maybe the above highlights it better.  That position with the last 4 (for 34) also where we start counting a 1 out of our 42 characters that we want to retrieve.  (Which is why we go from 4 to 2 on the second round of numbering, as the digit after is the 2nd digit we're keeping...)

Maybe I should've broke it down into two parts like this originally, but I wanted to illustrate that the second started where the first ended, *while including that end point*.  ;)
Title: Re: Trouble understanding MID$( )
Post by: Jaze on November 03, 2021, 12:00:25 am
QB64 doesn't handle the ":" character properly with string manipulation

Code: QB64: [Select]
  1. checkForTime$ = "6:30 AM"
  2. PRINT "|" + MID$(checkForTime$, 2, 1) + "|"
prints out the empty string i.e. || with nothing in between
Title: Re: Trouble understanding MID$( )
Post by: luke on November 03, 2021, 12:14:06 am
Quote from: Jaze on November 03, 2021, 12:00:25 am
QB64 doesn't handle the ":" character properly with string manipulation

Code: QB64: [Select]
  1. checkForTime$ = "6:30 AM"
  2. PRINT "|" + MID$(checkForTime$, 2, 1) + "|"
prints out the empty string i.e. || with nothing in between

No, it prints
Code: [Select]
|:|
Title: Re: Trouble understanding MID$( )
Post by: SMcNeill on November 03, 2021, 12:20:26 am
Have you went into libqb.cpp and made custom changes to MID$?  This is the second time you've reported it being buggy when things are working entirely as expected.
Title: Re: Trouble understanding MID$( )
Post by: FellippeHeitor on November 03, 2021, 12:38:16 am
What the heck, Jaze. Please do follow up on the discussion. Previous thread was even renamed, since MID$() is working exactly as expected for everyone but you.
Title: Re: Trouble understanding MID$( )
Post by: Jaze on November 03, 2021, 11:15:07 am
I wrote the code differently and don't have a copy of it, but it is definitely not working as it should all the time. When I run into another error with strings (which I inevitably will), I'll post the exact code, the results I got and the results I expected. Basically I was trying to determine if a string was a time. The only character that got the correct results was the first digit. Sorry for not being more specific, but like I said, I'll definitely write a more thorough post if (when) it happens again
Title: Re: Trouble understanding MID$( )
Post by: Jaze on November 03, 2021, 11:23:44 am
I was  able to undo to get the exact code. The string assigned to checkForTime$ is "6:30 AM". It is read from a text file using a LINE INPUT and then passed to the SUB with this code
Code: QB64: [Select]
  1.     IF LEN(checkForTime$) = 7 THEN
  2.         d1$ = Middle$(checkForTime$, 1, 1): digit1 = VAL(d1$)
  3.         colon$ = Middle$(checkForTime$, 2, 1)
  4.         d$2 = Middle$(checkForTime$, 3, 1): digit2 = VAL(d2$)
  5.         d3$ = Middle$(checkForTime$, 4, 1): digit3 = VAL(d3$)
  6.         aSpace$ = Middle$(checkForTime$, 5, 1)
  7.         aORp$ = Middle$(checkForTime$, 6, 1)
  8.         m$ = Middle$(checkForTime$, 7, 1)
  9.         COLOR 15, 0: LOCATE 1, 1: PRINT "checkForTime$ = |" + checkForTime$ + "|"
  10.         LOCATE 2, 1: PRINT d1$ + colon$ + d2$ + d3$ + aSpace$ + m$
  11.         t$ = P$(1)'wait for a key press
  12.         IF colon$ = ":" AND aSpace$ = " " THEN
  13.             IF (digit1 >= 1 AND digit1 <= 9) AND ((digit2 >= 1 AND digit2 <= 5) OR d2$ = "0") THEN 'AND
  14.                 IF ((digit3 >= 1 AND digit3 <= 9) OR d3$ = "0") THEN 'AND
  15.                     IF (aORp$ = "A" OR aORp$ = "P") AND m$ = "M" THEN
  16.                         timeThere = TRUE
  17.                     END IF
  18.                 END IF
  19.             END IF
  20.         END IF
checkForTime$ prints out at the top correctly
The line below it prints out "6" and nothing else
Title: Re: Trouble understanding MID$( )
Post by: FellippeHeitor on November 03, 2021, 11:27:40 am
The code you provided above doesn't use MID$(), and we have no idea what your custom Middle$() function is doing.
Title: Re: Trouble understanding MID$( )
Post by: FellippeHeitor on November 03, 2021, 11:30:34 am
to simply detect whether there's a colon in there, check:

Code: QB64: [Select]
  1. IF INSTR(checkForTime$, ":") > 0 THEN PRINT "There's a colon in this string"
Title: Re: Trouble understanding MID$( )
Post by: Jaze on November 03, 2021, 11:38:03 am
Sorry. I've run into a lot of bugs with strings so I wrote my own MID$ and named it Middle$().

Here's the code for it
Code: QB64: [Select]
  1. FUNCTION Middle$ (text$, startPosition, endPosition)
  2.     rtn$ = ""
  3.     newText$ = text$
  4.     FOR count = 1 TO startPosition - 1
  5.         newText$ = RIGHT$(newText$, LEN(newText$) - 1)
  6.     NEXT count
  7.     FOR count = startPosition TO endPosition
  8.         rtn$ = rtn$ + LEFT$(newText$, 1)
  9.         newText$ = RIGHT$(newText$, LEN(newText$) - 1)
  10.     NEXT count
  11.     Middle$ = rtn$
  13.  
Title: Re: Trouble understanding MID$( )
Post by: Cobalt on November 03, 2021, 11:40:42 am
Quote from: FellippeHeitor on November 03, 2021, 11:27:40 am
The code you provided above doesn't use MID$(), and we have no idea what your custom Middle$() function is doing.
@FellippeHeitor
I think he might be using the MIDDLE$ function Bplus or Steve made earlier in this thread. Still no mention on just what he is expecting.

@Jaze
Just what are you trying to accomplish? It is totally possible MID$ may not be the function you are looking for to do the work you need, but without knowing just what you want for output I don't think anybody is going to be able to address your exact issue.
We need to know what you need done to know just why your not getting it from the code.
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 03, 2021, 11:41:31 am
Quote from: Jaze on November 03, 2021, 11:23:44 am
I was  able to undo to get the exact code. The string assigned to checkForTime$ is "6:30 AM". It is read from a text file using a LINE INPUT and then passed to the SUB with this code
Code: QB64: [Select]
  1.     IF LEN(checkForTime$) = 7 THEN
  2.         d1$ = Middle$(checkForTime$, 1, 1): digit1 = VAL(d1$)
  3.         colon$ = Middle$(checkForTime$, 2, 1)
  4.         d$2 = Middle$(checkForTime$, 3, 1): digit2 = VAL(d2$)
  5.         d3$ = Middle$(checkForTime$, 4, 1): digit3 = VAL(d3$)
  6.         aSpace$ = Middle$(checkForTime$, 5, 1)
  7.         aORp$ = Middle$(checkForTime$, 6, 1)
  8.         m$ = Middle$(checkForTime$, 7, 1)
  9.         COLOR 15, 0: LOCATE 1, 1: PRINT "checkForTime$ = |" + checkForTime$ + "|"
  10.         LOCATE 2, 1: PRINT d1$ + colon$ + d2$ + d3$ + aSpace$ + m$
  11.         t$ = P$(1)'wait for a key press
  12.         IF colon$ = ":" AND aSpace$ = " " THEN
  13.             IF (digit1 >= 1 AND digit1 <= 9) AND ((digit2 >= 1 AND digit2 <= 5) OR d2$ = "0") THEN 'AND
  14.                 IF ((digit3 >= 1 AND digit3 <= 9) OR d3$ = "0") THEN 'AND
  15.                     IF (aORp$ = "A" OR aORp$ = "P") AND m$ = "M" THEN
  16.                         timeThere = TRUE
  17.                     END IF
  18.                 END IF
  19.             END IF
  20.         END IF
checkForTime$ prints out at the top correctly
The line below it prints out "6" and nothing else

This line is screwed up, I am curious why no error?
Code: QB64: [Select]
  1. d$2 = Middle$(checkForTime$, 3, 1): digit2 = VAL(d2$)
  2.  

This almost works or looks like something when MID$( is substituted back in for Middle$(
Code: QB64: [Select]
  1. checkforTime$ = "6:30 AM"
  2.  
  3. If Len(checkforTime$) = 7 Then
  4.     d1$ = Mid$(checkforTime$, 1, 1): digit1 = Val(d1$)
  5.     colon$ = Mid$(checkforTime$, 2, 1)
  6.     d2$ = Mid$(checkforTime$, 3, 1): digit2 = Val(d2$) ' <<< fix d$2 to d2$
  7.     d3$ = Mid$(checkforTime$, 4, 1): digit3 = Val(d3$)
  8.     aSpace$ = Mid$(checkforTime$, 5, 1)
  9.     aORp$ = Mid$(checkforTime$, 6, 1)
  10.     m$ = Mid$(checkforTime$, 7, 1)
  11.     Color 15, 0: Locate 1, 1: Print "checkForTime$ = |" + checkforTime$ + "|"
  12.     Locate 2, 1: Print d1$ + colon$ + d2$ + d3$ + aSpace$ + m$
  13.     t$ = P$(1) 'wait for a key press
  14.     If colon$ = ":" And aSpace$ = " " Then
  15.         If (digit1 >= 1 And digit1 <= 9) And ((digit2 >= 1 And digit2 <= 5) Or d2$ = "0") Then 'AND
  16.             If ((digit3 >= 1 And digit3 <= 9) Or d3$ = "0") Then 'AND
  17.                 If (aORp$ = "A" Or aORp$ = "P") And m$ = "M" Then
  18.                     timeThere = TRUE
  19.                 End If
  20.             End If
  21.         End If
  22.     End If
  24.  
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 03, 2021, 11:51:41 am
All fixed! ??
Code: QB64: [Select]
  1. checkforTime$ = "6:30 AM" '<<< watch out! some times have 2 digits at start like now 11:55 AM
  2. TRUE = -1
  3. If Len(checkforTime$) = 7 Then
  4.     d1$ = Mid$(checkforTime$, 1, 1): digit1 = Val(d1$)
  5.     colon$ = Mid$(checkforTime$, 2, 1)
  6.     d2$ = Mid$(checkforTime$, 3, 1): digit2 = Val(d2$) ' <<< fix d$2 to d2$
  7.     d3$ = Mid$(checkforTime$, 4, 1): digit3 = Val(d3$)
  8.     aSpace$ = Mid$(checkforTime$, 5, 1)
  9.     aORp$ = Mid$(checkforTime$, 6, 1)
  10.     m$ = Mid$(checkforTime$, 7, 1)
  11.     Color 15, 0: Locate 1, 1: Print "checkForTime$ = |" + checkforTime$ + "|"
  12.     'Locate 2, 1: Print d1$ + colon$ + d2$ + d3$ + aSpace$ + m$ ' <<<<<<<<<<<<<<<<<<<<<<<<<<<< missing aORp$ I think!
  13.     Locate 2, 1: Print d1$ + colon$ + d2$ + d3$ + aSpace$ + aORp$ + m$
  14.     t$ = P$(1) 'wait for a key press
  15.     If colon$ = ":" And aSpace$ = " " Then
  16.         If (digit1 >= 1 And digit1 <= 9) And ((digit2 >= 1 And digit2 <= 5) Or d2$ = "0") Then 'AND
  17.             If ((digit3 >= 1 And digit3 <= 9) Or d3$ = "0") Then 'AND
  18.                 If (aORp$ = "A" Or aORp$ = "P") And m$ = "M" Then
  19.                     timeThere = TRUE
  20.                     Print timeThere
  21.                 End If
  22.             End If
  23.         End If
  24.     End If
  26.  
Title: Re: Trouble understanding MID$( )
Post by: FellippeHeitor on November 03, 2021, 12:15:50 pm
Quote
This line is screwed up, I am curious why no error?

d2$ is the same as DIM d2 AS STRING
d$2 is the same as DIM d AS STRING * 2
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 03, 2021, 12:21:33 pm
Quote from: FellippeHeitor on November 03, 2021, 12:15:50 pm
d2$ is the same as DIM d2 AS STRING
d$2 is the same as DIM d AS STRING * 2

Wow, did not know that! Thanks

PS I am sure that was not Jaze intention, it was typo I bet.
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 03, 2021, 12:44:28 pm
I like a Middle$ routine, it's a nice one for toolbox and using Rtn$ is excellent substitute for Function name for QB64 v2.0+

Here is another way to do Middle$ without Left$, Right$, or that peculiar Mid$ ;-))
Code: QB64: [Select]
  1. s$ = "Middle$"
  2. For i = 1 To Len(s$)
  3.     Print Middle$(s$, 1, i),
  4.     Print Middle$(s$, i, Len(s$))
  6.  
  7. Function Middle$ (text$, startPosition, endPosition)
  8.     For i = startPosition To endPosition
  9.         rtn$ = rtn$ + Chr$(Asc(text$, i))
  10.     Next
  11.     Middle$ = rtn$
  13.  
  14.  
  15.  
Title: Re: Trouble understanding MID$( )
Post by: SMcNeill on November 03, 2021, 01:25:47 pm
Code: QB64: [Select]
  1. startTime = 34
  2. endTime = 42
  3. lineToPrint$ = "|                                 9:30 AM N-the lobby between 10:13 AM-N   |"
  4.  
  5.  timeString$ = MID$(lineToPrint$, startTime, endTime)

Code: [Select]
    IF LEN(checkForTime$) = 7 THEN
        d1$ = Middle$(checkForTime$, 1, 1): digit1 = VAL(d1$)
        colon$ = Middle$(checkForTime$, 2, 1)
From these two code snippets. it's obvious that Jaze has expectations that his code will read his mind.  In the first, he wants MID$ to work with a (string, start point, end point) syntax  In the second, he's expecting it to work with a (string, start point, number of characters) syntax. 

You can't have it both ways! 

MID$ itself works with the (string, start, number of bytes) syntax.  MIDDLE$, which you wrote yourself, works with the (string, start point, end point) syntax.  The two commands *AREN'T* interchangeable and you need to use the proper one to meet your expectations.

 
Since you posted code with using your custom MIDDLE$ sub, I'd imagine that the line in question should actually look like one of the two options below:
Code: QB64: [Select]
  1.         colon$ = Middle$(checkForTime$, 2, 2)
  2.         colon$ = Middle$(checkForTime$, 2, 3)

The proper one of those two variations will depend on exactly how you wrote your MIDDLE$ function.  If it's start point, end point, then 2, 2 will be fine.   If it's startpoint, endpoint - startpoint, then the 3,2 is probably what you need.   Regardless, you can't start at position 2 and then try to get the proper information back from that point to position 1 as the end point.  I doubt you wrote your code to read in reverse, so all you're going to get from 2, 1 with MIDDLE$ is a blank string "".  (Even if you did write it to read in reverse, you'd just get a "1" and not the ":" as you're reading from the opposite direction...)

Syntax on our commands doesn't change.  We can't expect it to conform to what we WANT it to be at our whimsey.  Write it consistently and you won't have issues with it.
Title: Re: Trouble understanding MID$( )
Post by: Jaze on November 03, 2021, 01:47:48 pm
I'm telling you, my strings aren't working right. I don't use graphics, I do everything in strings. Check out my CryptoGram.bas to see what I'm talking about. I posted it a while ago. I don't know if it's still on the boards. I'm pretty good with string manipulation. I admonish there's a possibility there was an error in my code but at this point I either don't know everything I need to (when a QB64 function takes a 'byte' as a variable for example), my computer has a personal issue with me or there's an internal error in QB64. I rewrote that portion of the code a little differently but the files the LINE INPUTs come from has a lot of text and also times. The idea was to make sure that the only thing to code for was at a specific place in the input line and that it was definitely a time at that location. If something in the future that gives me significant difficulty, I'll post it.
Title: Re: Trouble understanding MID$( )
Post by: SMcNeill on November 03, 2021, 02:15:09 pm
Here's my first attempt at writing a little code to extract time from a string; see if it'd be suitable for your needs:

Code: QB64: [Select]
  1. test$ = "The time was " + Time$ + "."
  3. test$ = test$ + "  The time is now " + Time$ + "."
  4. Print test$
  6.     tyme$ = GetTime$(test$, p)
  7.     If tyme$ <> "" Then Print tyme$: p = p + 1
  8. Loop Until tyme$ = ""
  9.  
  11. test$ = "My ratio is 1:2.  " + test$ + "  And my updated time is " + Time$
  12. p = 0
  13. Print test$
  15.     tyme$ = GetTime$(test$, p)
  16.     If tyme$ <> "" Then Print tyme$: p = p + 1
  17. Loop Until tyme$ = ""
  18.  
  19. Function GetTime$ (text$, position)
  20.     FirstColon = InStr(position, text$, ":")
  21.     If FirstColon Then 'If we have one colon then
  22.         SecondColon = InStr(FirstColon + 1, text$, ":")
  23.         If SecondColon - FirstColon <> 3 Then 'it's not a proper time.
  24.             position = FirstColon + 1
  25.             GetTime$ = GetTime$(text$, position) 'check to see if we have a proper time AFTER the false occurance.
  26.             Exit Function
  27.         End If
  28.         GetTime$ = Mid$(text$, FirstColon - 2, 8)
  29.         position = SecondColon
  30.     End If

What this does is look for the essential two middle colons of our time and then grab the proper 8 digits from those reference points.   Something like 1:12 wouldn't work, as it'd be at least expecting to see the time in a HH:MM:SS format.

This doesn't look for, or grab "AM" or "PM" references, as it's basically expecting TIME$ type formats, and those are in 24-hour times. 

There's no real error checking to see if we generate false positives with this method (such as grabbing AT:14:XP), as I'm keeping the basic process as simple as possible for illustration's sake.  This type of thing doesn't have to be difficult at all, if you just stick to the basics of what you're expecting with it.

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Title: Re: Trouble understanding MID$( )
Post by: bplus on November 03, 2021, 03:10:19 pm
@Jaze Simple tests for your computer and your QB64 copy:

Use Mid$ to print the two ll's in "Hello World"
Print Mid$("Hello World", 3, 2)

Use Mid$ to print the word World from "Hello World"
Print Mid$("Hello World", 7, 5)
or just
Print Mid$("Hello World", 7)
Title: Re: Trouble understanding MID$( )
Post by: George McGinn on November 03, 2021, 03:11:00 pm
I find it easier to just split the string based on a delimiter, then look through the results (an array that is populated by my strSplit$ FUNCTION) for the section that I need.

Here is my STRSPLIT$ FUNCTION, which populates an array named Query (declared as STRING SHARED). A string (qString$) and a delimiter (Delim$) is passed to the function.

The thing is, MID$ works properly. I use this to parse results from mySQL query results.

Code: QB64: [Select]
  1. FUNCTION StrSplit$ (qString$, Delim$)
  2. '-----------------------------------------------------------------------------
  3. ' *** Split a STRING based on provided Delimiter
  4. ' ***      qString$ and Delim$ are passed to this function
  5. '
  6.         lenstr = LEN(qString$)
  7.         idx = 1
  8.         startpos = 1
  9.         DO
  10.                 findpos% = INSTR(findpos% + 1, qString$, Delim$) ' find another occurance
  11.                 IF findpos% THEN
  12.                         nbrbytes = findpos% - startpos
  13.                         Query(idx) = MID$(qString$, startpos, nbrbytes)
  14.                         startpos = findpos% + 1
  15.                         idx = idx + 1
  16.                 END IF
  17.         LOOP UNTIL findpos% = 0
  18.         nbrbytes = lenstr - startpos + 1
  19.         Query(idx) = MID$(qString$, startpos, nbrbytes)
  20.        
  21.         StrSplit$ = "0"
  22.  
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 03, 2021, 03:20:59 pm
Here's how I would convert a Time$ format (hh:mm:ss)
Code: QB64: [Select]
  1. T$ = Time$
  3. hrs = Val(Mid$(T$, 1, 2))
  4. mins = Val(Mid$(T$, 4, 2))
  5. secs = Val(Mid$(T$, 7, 2))
  6. If hrs > 11 Then m$ = " PM" Else m$ = " AM"
  7. If hrs > 12 Then hrs = hrs - 12
  8. Print hrs; mins; secs; m$
  9.  
  10.  

Now you're ready to build an analog clock! ;-))
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 03, 2021, 03:42:52 pm
Quote from: Jaze on November 03, 2021, 01:47:48 pm
I'm telling you, my strings aren't working right. I don't use graphics, I do everything in strings. Check out my CryptoGram.bas to see what I'm talking about. I posted it a while ago. I don't know if it's still on the boards. I'm pretty good with string manipulation. I admonish there's a possibility there was an error in my code but at this point I either don't know everything I need to (when a QB64 function takes a 'byte' as a variable for example), my computer has a personal issue with me or there's an internal error in QB64. I rewrote that portion of the code a little differently but the files the LINE INPUTs come from has a lot of text and also times. The idea was to make sure that the only thing to code for was at a specific place in the input line and that it was definitely a time at that location. If something in the future that gives me significant difficulty, I'll post it.

I dug up that old post, CryptoGram.bas, and commented on your use of Mid$ there.
https://www.qb64.org/forum/index.php?topic=4166.msg137774#msg137774
Title: Re: Trouble understanding MID$( )
Post by: eekee on November 07, 2021, 02:39:58 am
This looks very much like the sort of errors I used to make for years. I felt like I was getting on all right, but I commonly mis-remembered syntax or started doing something differently and didn't notice. I often couldn't see anything wrong even when it was something very simple. Despite this, I could still type mostly coherent English and my programming errors tended to only show in one specific thing. Typically for me, it was regular expressions.

As such, I respectfully suggest the OP get more fresh air. Carbon dioxide -- the stuff we breathe out -- builds up fast and has a surprisingly stong affect on brain function. I forget the exact figures, but it's easy to build up enough carbon dioxide to halve brain function. Bedrooms have been known to build up even more than that. Ventilation is essential. Sadly, it's sometimes impossible to get enough ventilation; some entire valleys develop unacceptably high carbon dioxide levels on still days. It must also be noted that microbes which consume organic detritus (dirt) also produce carbon dioxide.

As to why this is showing up with MID$ specifically, I recall it being the hardest function to understand when I was little. I don't know why, it just was. I hated it for a while.
Title: Re: Trouble understanding MID$( )
Post by: Aurel on November 07, 2021, 04:28:02 am
what ,what and what
i must say that i am surprised with MID$
it is such a simple and elegant string function which return subString ...right?

mark says :

mid$( t$, len) ..yes it is ok but not for everyone....it should be standard

MID$ ( target_string, start_Pos, Len_Of_substring)
Title: Re: Trouble understanding MID$( )
Post by: bplus on November 07, 2021, 08:53:43 am
Quote from: Aurel on November 07, 2021, 04:28:02 am
what ,what and what
i must say that i am surprised with MID$
it is such a simple and elegant string function which return subString ...right?

mark says :

mid$( t$, len) ..yes it is ok but not for everyone....it should be standard

MID$ ( target_string, start_Pos, Len_Of_substring)

Nope, nope and nope! :) This is incorrect:
Quote
mark says :

mid$( t$, len) ..yes it is ok but not for everyone....it should be standard

For section of string that starts at Start_Position and ends with the end of Text$ use:
MID$( Text$, Start_Position )  ' < and let IDE correct spacing
no LEN or lengths are needed for 2 parameter MID$ function.

Well I hope we don't have everyone confused now ;-))

MID$ Statement (Sub) is really nice too! It will increase speed over concatenation.

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