Unsupplied Value

The Unsupplied class implements the value used to initialize unsupplied keyword parameters to functions. There is one distinguished instance of the Unsupplied class in the reserved system variable unsupplied. You can test to see whether a caller has supplied an optional keyword argument by comparing it with unsupplied.

Constructor

Unsupplied

 

Examples

fn walk_tree obj parent: =

(

if parent == unsupplied then

...

else

...

...

)

See also

Creating Functions

Function Calls

FAQ: What is the difference between 'undefined' and 'unsupplied' values?