Re: Lookup Table

["Ruud H.G. van Tol" <rvtol@isolution.nl>]

On 2023-11-24 08:16, Thomas D. Dean wrote:
> I want to create a sparse lookup table with a key and value or key and 
> set.
> When I do table[N], or a function call, I want to get back either 1 or 
> 0. Another use, I want to return a set, {1,2,3,...} or {}.
>
> For example, I want table[N] to return 0 if entry N exists or 1 if it 
> does not.
>
> I tried
> ? M=Map();
> %131 = Map([;])
> ? mapput(~M,7,0)
> ? mapget(M,7)
> %133 = 0
>
> Does mapget(M,7) use pass by value or is M passed by reference?
>
> ? mapget(M,8)
>   ***   at top-level: mapget(M,8)
>   ***                 ^-----------
>   *** mapget: nonexistent component in mapget: index not in map
>   ***   Break loop: type 'break' to go back to GP prompt
>
>
> Is it possible to do this?

For maps, there is mapisdefined( map, key, {&value} ).
And the value can be a set.

See also
https://pari.math.u-bordeaux.fr/pub/pari/manuals/2.15.4/users.pdf

-- Ruud