[Seed7-users] Sorting an array of array with a custom compare function

[Stéphane G. <ste...@wa...>]

Hello,

   I would like to sort a table of rows, depending on the content of the 
second cell of a row.

* A Row is an array of strings.

* The table is an array of rows.

* I want to sort table.

* So I need to compare Rows.

* So I thought I had to implement a compare() function that takes Rows as 
arguments and compares the specific string cell I desire.


  Here is the code I tried:

----------------------------
$ include "seed7_05.s7i";
   include "stdio.s7i";


const type: Row is array string;

const func integer: compare(in Row: A, in Row: B) is
 	return compare(A[2], B[2]);

const proc: main is func
local
 	var array Row : table is [] ( [] ("CCC", "BBB"), [] ("CCC", "AAA"), [] ("AAA", "CCC"));
 	var Row : r is 2 times "";
begin
 	for r range table do
 		writeln(r[1] & "  " & r[2]);
 	end for;

 	table:=sort(table);
 	writeln("-----------");

 	for r range table do
 		writeln(r[1] & "  " & r[2]);
 	end for;

end func;
----------------------------

   And it fails to compile, complaining that I redeclare the compare() 
function:

----------------------------
  ~/test/seed7 $s7c compare_array.s7
SEED7 COMPILER Version 3.0  Copyright (c) 1990-2018 Thomas Mertes
Source: compare_array.s7
Compiling the program ...
*** compare_array.s7(8):34:  (ref TEST_3 param, ref TEST_3 param) compare 
declared twice
         return compare(A[2], B[2]);
-----------------------------------^
1 error found
----------------------------

   I imagine it has something to do with my Row type being not a true 
separate type, but rather some kind of alias to array? (I am knew to the 
language so I don't know if that even makes sense ;-) )

   Anyway, what would be the right way(s) to achieve my goal?


Faithfully yours,
   Stéphane Goujet.