According to FPL:

This appear not to be a GPC relevant question, sorry.

Cannot we define set of record?

No.

type cellule = record x, y : integer; age : integer; end; population = set of cellule;

This does not compilate, is it a language non sens?

The Pascal language only allows sets of ordinal types (Integer, Char, Boolean, enumerated types). The best approximation of what you are looking for is probably a dynamic array (schema) of `cellule's:

type cellule = record x, y : integer; age : integer; end;

population ( nmax : integer ) = array [ 1..nmax ] of cellule; population_ptr = ^population;

var cellules : population ( 1000 ); plus_cellules : population_ptr;

...

new ( plus_cellules, 10000 );

GPC, however, allows to redefine the `in' operator to act between, say one `cellule' and a `population_ptr'.

operator in ( c : cellule; p : population_ptr ) = result : boolean;

begin (* cellule in population_ptr *) <some loop which calculates `result'> end (* cellule in population_ptr *);

Have fun,

Peter