OpenEuphoria

Re: File I/O Difficulty

• Posted by "Graeme." <hmi at POWERUP.COM.AU> Jun 20, 1998
• 796 views

At 05:32 PM 6/19/98 -0400, you wrote:
>---------------------- Information from the mail header -----------------------
>Sender:       Euphoria Programming for MS-DOS <EUPHORIA at LISTSERV.MUOHIO.EDU>
>Poster:       Alan Tu <ATU5713 at COMPUSERVE.COM>
>Subject:      File I/O Difficulty
>-------------------------------------------------------------------------------
>
>I am trying to read a file in for alteration on a byte-by-byte level.
>
>-----filedemo.ex
>include file.e
>include input.e
>clear_screen()
>sequence s
>integer file_i, file_o, seek_success
>s = input("Enter input path and filename: ")
>file_i = open(s, "rb")
>sequence file_proc
>integer file_length
>cseek_success = seek(file_i,-1)
>file_length = where(file_i)
>seek_success = seek(file_i,0)
>
>for x = 1 to file_length do
>    file_proc[x] = getc(file_i)
>end for
>-----end filedemo.ex
>
>Well, I got an error.
>
>-----ex.err
>
>crypt.ex:15
>variable file_proc has not been assigned a value =
>
>=2E..
>-----end ex.err
>
>Taking the hint, I then assigned to sequence file_proc to an empty sequen=
>ce
>before I entered the for loop.  Well, it complained that I was assigning
>something to a 0-length sequence.  This makes sense, only I expected my
>program would allocate storage dynamicly.
>
>So, would someone please tell me how to resolve this error?  Or, if anyon=
>e
>has a better suggestion, please let me know too.
>
>Thankx
>
>Alan


You are addressing specific elements of the
sequence file_proc that don't exist by using:
file_proc[x]=

if x=1 and file_proc={} then you are attempting
to write to element 1 of a zero length sequence.

To initialze the sequence for this kind of
access use:
file_proc=repeat(0,file_length)

However it might be neater to initialize
file_proc as {} and change the
"file_proc[x]=getc(file_i)" line to:

file_proc=file_proc&getc(file_i)

Graeme.
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