Clear the memory in order to have the subsequent code running in a clean environment.

kill(
    all
);

Calculate reaction forces at supports A and B

rotAeq : - F*a + YB*(a+b)=0;

ideally,
":"( rotAeq , - F*a + YB*(a+b)=0 );

vteq : +YA+YB-F=0;

rotAeq;

sols : linsolve( [rotAeq , vteq] , [YA,YB] );

sols;

evaluations:

 log(pippo^2+clarabella) , pippo=3*%e , clarabella=2.3 , numer ;

ideally, an 
ev( 
opens each typed instruction, and
a 
) 
closes it.

[YA,YB] : ev([YA,YB] , sols);