External: SIGSEGV
lazarus / 62-General

----------------------------------------------------------------------
tgd · 2015-09-22 10:34

Hi, I'm not sure if this is the right section for this, but here it
is:
Code: [Select]program project1;
var
a,b,n:integer;
mat:array of array of real;
F:textfile;
begin
  write('n=');
  readln(n);
setlength(mat,n,n);
assign(F,'C:\Users\Julius\Desktop\fps\aaa.txt');
reset(F);
for a:=1 to n do
    for b:=1 to n do
        read(F,mat[a,b]);
close(F);
end.
The program is supposed to compute the inverse matrix to the matrix
from the text file. I actually wrote the whole thing and it works, but
now I'm trying to use dynamic arrays. When I run the program, I choose
the n value, press enter and get an error message saying that project1
raised exception class External:SIGSEGV at the line with
'read(F,mat[a,b]);'.
Any help would be appreciated. Thanks.

----------------------------------------------------------------------
Jonas Maebe · 2015-09-22 11:14

The indices in a dynamic array run from 0 to length-1, not from 1 to
length. The safest way to iterate over all array positions, which
works with any kind of array, is to always use something like

Code: [Select]for a:=low(mat) to high(mat) do
  for b:=low(mat[a]) to high(mat[a]) do
     ...

----------------------------------------------------------------------
tgd · 2015-09-22 11:27

It works now, thanks a lot!