Availability:built-in
nb_current(?Name, 
?Value)Enumerate all defined variables with their value. The order of 
enumeration is undefined. Note that nb_current/2 
can be used as an alternative for nb_getval/2 
to request the value of a variable and fail silently if the variable 
does not exists. Note that if the variable is not defined, exception/3 
is called attempting to define it. As of version 8.3.28, a failure of exception/3 
to define the variable causes the variable to be defined with a reserved 
valued to avoid subsequent calls to exception/3.