4.7 Type Checks

The types of values can be checked in Oz dynamically, as illustrated by the following examples.

{Inspect {IsRecord R}}
{Inspect {IsRecord F}}
 
{Inspect {Or {IsRecord ~100}
          {IsBool ~100}}}
{Inspect {And {And
               {IsNumber ~100}
               {IsInt ~100}}
          {IsFloat ~100}}}
 
{Inspect {Not {IsRecord false}}}
{Inspect {IsRecord {IsRecord false}}}
 
{Inspect {And
          {And
           {IsList L}
           {IsTuple L}}
          {IsRecord L}}}
 
 

It might be surprising that the Unit, the Booleans, and atoms are records. The reason is that a record need not to have subrecords.

There also exists a predefined procedure in Oz which computes the type of a given value. This is the procedure Value.status. When applied, it return not only the type of its input argument but also its actual status which may be either determined, kinded, or free.

{Inspect [{Value.status R}
          {Value.status T}
          {Value.status L}
          {Value.status F}]}
 
 

For functional programming, we'd better deal only with values of status `determined', in order to avoid suspensions (blocking computations).