Computer Science Canada

Substring error message
Author:  Adalias [ Thu Jan 11, 2007 10:58 am ]
Post subject:  Substring error message
I am making a word processor program that takes in a chunk of text and justifies it left, center, right, full, and snake (like a newspaper). I haven’t gotten very far but here’s what I’ve got:

code:

var justification, line, current : string := ""
var col, istart, jstart : int := 1
istart := 1
jstart := 1
put "What type of justification do you want?"
put "left, center, right, full or snake?"
get justification
if justification = "left" or justification = "right" or justification = "full" or justification= “center” then
    put "What length of line would you like?"
    get col
end if
if justification = "left" then
    put "Enter the line you would like to justify"
    get line : *
    for i : istart .. length (line)
        for j : jstart .. length (line)
            if line (j) = " " then
                if (length (current) + length (line (i .. j))) <= col then
                    current := current + line (i .. j)
                    istart := j
                    exit
                else
                    put current
                    current := ""
                    put ""
                end if
            end if
        end for
    end for
end if



I know you're probably seeing a lot of errors and ways to make it better and whatnot, but all I need help with is this one error. Run it the way it is and it will work, asking for the type of justification (left is the only one I've got atm) and length of the lines (I use 20), but right after entering the line it crashes with the error:

Left bound of substring exceeds right by more than 1.

While highlighting line 18

if (length (current) + length (line (i .. j))) <= col then

I'm sure there is a very simple answer to this problem but try as I might I just can't seem to find it. Any help would be appreciated
Author:  Ultrahex [ Thu Jan 11, 2007 9:53 pm ]
Post subject:  Re: Substring error message
your instructions on how to use the program were not very well

i was confused about what it meant by
"Enter the line you would like to justify" anyhow...

Ok, the problem occurs because you cant have 20 lines of text for a sentence that is only 20 long.

or something like that, you are trying to justify it left???

Turing:
var justification, line, current : string := ""
var col, istart, jstart : int := 1
var isEOL : boolean := false
istart := 1
jstart := 1
put "What type of justification do you want?"
put "left, center, right, full or snake?"
get justification
if justification = "left" or justification = "right" or justification = "full" or justification = "center" then
    put "What length of line would you like?"
    get col
end if

if justification = "left" then
    put "Enter the line you would like to justify"
    get line : *
    for j : 1 .. length (line)
        if j mod col = 0 or isEOL = true then
            isEOL := true
            if line (j) = " " then
                put ""
                isEOL := false
            else
                put line (j) ..
            end if

        else
            put line (j) ..
        end if
    end for
end if


That is how i would attempt to do, BTW i made it so it writes that last word still and when it gets to next space it goes to next line, however you could do it the otherway and backtrace.
Author:  Clayton [ Thu Jan 11, 2007 10:14 pm ]
Post subject:  Re: Substring error message
Your error means that the left or lower bound of your substring (the length(current (i..j))) is greater than the upper or right bound of the substring. In other words, i becomes higher than j, and that's not good, I think you want to have it the other way around ( length(current(j..i)) )
Author:  [Gandalf] [ Fri Jan 12, 2007 6:11 pm ]
Post subject:  RE:Substring error message
Or alternatively and more flexibly:
Turing:
length (current (min (i, j) .. max (i, j)))
Author:  Adalias [ Wed Jan 17, 2007 2:09 pm ]
Post subject:  Re: Substring error message
Thanks Ultrahex that helped alot.

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