Writing data stream to text file

[tobx]

Hey LiveCode! I'm trying to figure out how I can record the long time to a text file each time a user presses the space bar. Here is what I currently have:

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on keyDown spacebar
   if the enableAddScore of this card = "true" then add 1 to gscore
   put gscore into field "Score"
   ##testing save stuff
   write the long time & tab to file tFile at end
   set the enableAddScore of this card to "false"
end keyDown

tFile is accurate and already open for append from a previous stack but this code I currently have is not writing the long time + tab whenever the user presses the space bar. Any tips?

[zaxos]

Code: Select all

on keyDown spacebar
   if the enableAddScore of this card = "true" then add 1 to gscore
   put gscore into field "Score"
   ##testing save stuff
   write the long time & tab to file tFile at end
   put the result -- this could give you a clue
   set the enableAddScore of this card to "false"
end keyDown

[Klaus]

Hi all,

"keydown" get send whenever the user type ANY character on his keyboard!
The parameter that come with "keydown" is the actual key the user pressed,
which may or may not be a SPACE!

So you first need to sort out any other keys like this, or this will happen when pressing ANY key:

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on keyDown tKey
  if tKey <> SPACE then
    pass keydown
  end if

   ## NO need to QUOTE TRUE/FALSE, same for numbers!
   if the enableAddScore of this card = TRUE then 
      add 1 to gscore
   end if
   put gscore into field "Score"
   
  ## I prefer the shorter URL syntax, no need to open or close the file etc. 
  put (the long time & TAB) AFTER url("file:" & tFile)

  set the enableAddScore of this card to FALSE
end keydown

Best

Klaus

[tobx]

I see, the put + URL combo really cleans things up (and is easier to read for revision). Thanks for the suggestions, zaxos and Klaus! The data stream is working flawlessly!

[FourthWorld]

While the URL syntax is much easier to read, for append operations my understanding is that the convenience it offers the scripter comes at a significant cost to performance. IIRC it treats the file contents as a complete chunk, so "put after" will first read the entire file, append the data in memory, then write the whole thing out again. In contrast, when a file is first opened in append mode it will only write to the end of the file, so none of the data written previously is ever touched by subsequent writes.

I tested this hypothesis with the following code. Try a few runs with different values in the variable n defined on the first line. At 10 iterations "put URL" is still slower than "open for append" but not bad. However, as you increase the number of iterations to 1000 or 10000 the time for AppendData1 grows exponentially, whereas time for AppendData2 grows linearly:

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on mouseUp
   put 1000 into n
   put "This is a test" into s
   put specialFolderPath("desktop")&"/TestDumpFile1.txt" into tFile1
   put specialFolderPath("desktop")&"/TestDumpFile2.txt" into tFile2
   --
   -- "put URL"
   put the millisecs into t
   repeat n
       AppendData1 s, tFile1
    end repeat
    put the millisecs - t into t1
    --
    -- "open for append"
    put the millisecs into t
    open file tFile2 for append
    repeat n
       AppendData2 s, tFile2
    end repeat
    close file tFile2
    put the millisecs - t into t2
    --
    put url ("file:"& tFile1) into tData1
    put url ("file:"& tFile2) into tData2
    put "URL: "& t1 &" ms"&cr& "Append: "& t2 &" ms"&cr \
    &"Files the same? "& (tData1 = tData2)
end mouseUp


on AppendData1 s, tFile
   put s&cr after url ("file:"& tFile)
end AppendData1

on AppendData2 s, tFile
   write s &cr to file tFile
end AppendData2

For tasks done infrequently it probably doesn't matter much which form you use, but for extremely frequent tasks like file I/O on every keystroke the speed will eventually make a noticeable difference as the size of the data in the file grows.

[tobx]

but for extremely frequent tasks like file I/O on every keystroke the speed will eventually make a noticeable difference as the size of the data in the file grows.

This is exactly what I'm doing and noticing so back to "write ... at end" it is. Awesome breakdown and demo, thanks so much!

While we're here, can anyone spot what's wrong with this line?

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put statround(ypercent / 100 * ticketvalue) into yticketswon

I keep getting the following error: "execution error at [this line] (Operators /: error in left operand), char 1"

I tried removing the extra spaces and checked the variables being used and still no luck. This output is vital to the data stream!

[Klaus]

HI tobx,

hm, must be something else, syntax is correct, just made little test:

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on mouseUp
   put 100 into ypercent
   put 100 into ticketvalue
   put statround(ypercent / 100 * ticketvalue) into yticketswon
   answer yticketswon
end mouseUp

and got 100 as exspected, no errors!


Best

Klaus

[FourthWorld]

but for extremely frequent tasks like file I/O on every keystroke the speed will eventually make a noticeable difference as the size of the data in the file grows.

This is exactly what I'm doing and noticing so back to "write ... at end" it is. Awesome breakdown and demo, thanks so much

Glad that was helpful.

FWIW, when opening a file in append mode it will only write to the end of the file, so in those cases "...at end" isn't needed with the write command. Doesn't hurt if it's there, it just doesn't doesn't do anything that isn't already handled by the file opening mode.

[tobx]

"...at end" isn't needed with the write command.

Guess I was being too careful with that addition. Can't afford to lose any data for this study, noted! Thanks for all your help everyone! This community is AWESOME!

I'm still stuck on this line. I copy-pasted from Klaus to be sure I'm not doing anything weird:

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put statround(ypercent / 100 * ticketvalue) into yticketswon

Execution error in left operand, char 1. What does this even mean? Char 1 is the very beginning of the line, right? The first character of this like is the "p" in "put!"

[jacque]

Does ypercent have a numerical value?

[tobx]

Does ypercent have a numerical value?

Wow, I'm really dumb. I had a line putting numbers & "%" into ypercent. I removed it and now everything works. Thanks so much for the suggestion!

[jacque]

Lol. Been there, done that.