Maple 13: how to turn true to 1 and false to 0?

Question

In general, I need type conversion instructions that can, for example, be multiplied by true, as 5 * truewell as receive 5, for example x * false, and receive 0.

How to do it?

Answer 1

There are several ways to get this effect, and what you choose may depend on more details about what you intend to do with it.

The simplest is to use a 2 argument eval(or subs, since the evaluation should happen due to automatic simplification for a product with an exact 1 or 0).

> eval( 5*true, [true=1,false=0]);
                           5
> eval( x*false, [true=1,false=0]);
                           0

And of course, you can create a procedure to handle this assessment,

> T := expr -> eval(expr,[true=1,false=0]):

> T( 5*true );
                           5
> T( x*false );
                           0

(, , " " ) *.

. * "true" "false" , , . ( , "true" "false" , , . .)

> M:=module() option package; export `*`;
>  `*`:=proc(ee::seq(anything))
>         :-`*`(op(eval([ee],[true=1,false=0])));
>       end proc;
> end module:

> with(M):

> 5*true;
                           5
> x*false;
                           0

> a*b*c;
                         a b c

> eval( %, b=false ); # this doesn't play along
                       a false c

, "false" 0. , a * b * c ( a, b c) : - *, *. b = false *. , , ( , , "" - , ),

> M:=module() option package; export `*`;
>   `*`:=proc(ee::seq(anything))
>          local res;
>          res:=:-`*`(op(eval([ee],[true=1,false=0])));
>          if type(res,:-`*`) then
>            'procname'(op(res));
>          else
>            res;
>          end if;
>        end proc;
> end module:

> with(M):

> 5*true;
                           5
> x*false;
                           0

> a*b*c;
                     `*`(`*`(a, b), c)

> eval( %, b=false );
                           0

, * (* (a, b), c), *. , b = false , *, . (, , .)

Answer 2

subs([false=0, true=1], expr);