Flexible arrays and input and output

[jondmml]

I have a program that creates a flexible array and then outputs it to a file. I wish to retrieve this flexible array and am unsure how to approach this problem since I do not know how large the array is. Is there any way to open the array or should I just write a variable stating the array size? Thanks,

Jon

[CodeMonkey2000]

Use a flexible array and keep increasing the bounds of the array until you hit the eof (end of file).

[jondmml]

Thanks for the quick response. The only thing is, I think you misinterpreted my question. The file consists of a flexible array. I don't think I can read out line after line of an array using the method you suggested. For the time being, I just store a variable with the length of the flexible array, however, there must be a better way.

[[Gandalf]]

I'm not sure exactly what problem with reading in the data you're describing, but based on what you've said so far just follow this pseudo-ish code and you'll be fine:

code:

open file var foo : flexible array 1 .. 0 of element while not eof     increase size of foo by 1     set top element of foo to value in file     move down one line or across one word

The key is to start the array at size 0, and increase the size as long as the file contains more elements.

[Cervantes]

jondmml @ Fri Mar 09, 2007 1:19 pm wrote:

Thanks for the quick response. The only thing is, I think you misinterpreted my question. The file consists of a flexible array. I don't think I can read out line after line of an array using the method you suggested. For the time being, I just store a variable with the length of the flexible array, however, there must be a better way.

You say the file contains a flexible array. What exactly does that mean? It probably means it contains a bunch of data, one line for each element in the array, or something like that. That accounts for most of the data stored in the flexible array. There are two other pieces of data stored by the flexible array, though: the upper and lower bounds. Thus, you might want to include that data in your file, probably at the very start. However, think about the problem you're working on in a broader sense and determine if this is really necessary. At the very least, writing the size of the array would make loading the array from the file faster. It takes a fair bit of work to resize a flexible array.

(There's actually another piece of information stored by the flexible array. That's the type. However, you probably won't have to worry about writing that to the file.)

[jrblast]

I think he means he creates a flexible array and then just uses the write command to store it all in the datafile with just one line of code. You can write to the file this way with no problems but when you want to read it you dont know the upper bound. The easiest solution I can think of is just write the flexible array to the file:

code:

stuff write : fileStream, flexibleArray more stuff

and then have a loop to read it, include exit when eof (fileStream), increase the upper bound, read to a seperate, non array, variable and make the upper bound of the flexible array equal to that. Heres some sample code I made to show you how this works.
Writing to the file:

code:

var flex : flexible array 1 .. 0 of int for i : 1 .. 10             %give values to the array, in this case we are using some perfect squares     new flex, i     flex (i) := i ** 2     put flex (i) end for var dataStream : int := 0 open : dataStream, "test.dat", write write : dataStream, flex        %write the array to the file close : dataStream

Reading the file:

code:

var flex : flexible array 1 .. 0 of int var input : int var up : string var dataStream : int := 0 open : dataStream, "test.dat", read loop     exit when eof (dataStream)     new flex, upper (flex) + 1     read : dataStream, input     flex (upper (flex)) := input     put flex (upper (flex)) end loop close : dataStream