[eclipse-clp-users] About operations over Lists, search space function and something about indicators

Hello everyone, i've a problem with list... i need change a specific 
value on list, for example,

X=[5,4,3,2,1]... how can i change the 2nd value (4) for another one (7) 
whitout change any more over list?.

NewX=[5,7,3,2,1]
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about search space... is this function

search_space(Vars, Size) :-
    ( foreach(V,Vars), fromto(1,S0,S1,Size) do
        S1 is S0*get_domain_size(V)
    ).
 correct to get the search space?, i saw another one like this

search_space(Vars, Size) :-
    ( foreach(V,Vars), fromto(1,S0,S1,Size) do
        get_domain(V,D),
        S1 is S0*get_domain_size(D)
    ).

but i get errors on get_domain_size (/type error/)...
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and last... wich indicators do you think are more important or relevant 
when i get a snapshot?

i was thinking about backtracks, search space... but need more 'cos this 
are not enought for my investigation.

thanks a lot.