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· Aug 13, 2021

How to handle null values within a list

#Beginner #ObjectScript #InterSystems IRIS

Hi All I am a beginner and I am learning Objectscript and I would appreciate a steer regarding a problem I am solving.

The issue I have spent some time on resolving without success is that I have the stream listed below and as you can see it has some gaps in it.

Stream



das
is
wp

dsa
nmk

Here is the import method

IF ##class(%File).Exists(dir) '=1 {
    write !, "Unable to Open: "_dir
    QUIT
} ELSE {
    write "File: "_dir_" is open"
}
// instantiate a new class called file
set file = ##class(%Stream.FileCharacter).%New()
// create a new variable called sc
set sc = file.LinkToFile(dir)
set count=1
WHILE ('file.AtEnd) {
    set delim=" "
    set line = file.ReadLine()
    set i=1
    write !, "Loop started"
    write *32
    if (line '="") {
        write !, "Read started"
        write *32
        set ^answers(count)=$LISTFROMSTRING(line, delim)
        write *32
        set ^attempt(count)=^attempt(count)_$ZHEX(($ASCII($LIST(^answers(count)))))
        write "Attempt:", ^attempt(count) ,!
        set countdown=$LENGTH(line,delim)
        set i=$INCREMENT(i)
        set count=$INCREMENT(count)
    }
}

Reading from streams is sequential and I have been trying to find a way of using LISTFROMSTRING to read these values. The issue is that I have been having some trouble trying to account for the blank spaces and they stop the program from running in its tracks. I have tried using $EXTRACT and $PIECE and I want to be able to remove these null spaces when writing the lines out to the subscripted variable.

What would be the best way of reading in the values whilst bearing in mind that I don't want to have any blank spaces within any list I create?

BTW I am open to using globals, arrays or local variables

Thanks in advance and I really do appreciate any assistance on this.

Product version: IRIS 2021.1
$ZV: IRIS for UNIX (Ubuntu Server LTS for x86-64 Containers) 2021.1 (Build 215U) Wed Jun 9 2021 12:37:06 EDT
Discussion (6)0
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Eduard Lebedyuk · Aug 13, 2021

What do you want your $list to look like?

If you want the end result to be like this:

$lb("das", "is", "wp", "dsa", "nmk")

try this code (assumes dir is shorter that 3 641 144 chars):

ClassMethod test(dir = "test.txt")
{
    set file = ##class(%Stream.FileCharacter).%New()
    set file.LineTerminator = $c(1)
    do file.LinkToFile(dir)
    
    set str = file.Read($$$MaxStringLength)
    
    kill file
    
    set separator = $c(13,10)
    do {
        set newstr = str
        set str = $replace(str, separator _ separator, separator)
    } while newstr'=str
    
    set:$e(str, 1, $l(separator))=separator str=$e(str, 1 + $l(separator), *)
    set:$e(str, *-$l(separator)+1, *)=separator str=$e(str, 1, *-$l(separator))
    set list = $lfs(str, separator)
    quit list
}

This is a naive implementation assuming you don't care about the speed.

Faster solution would go through file line by line.

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