class X::NYI is Exception { }

Error class for unimplemented features. NYI stands for Not Yet Implemented.

If a Raku compiler is not yet feature complete, it may throw an X::NYI exception when a program uses a feature that it can detect and is somehow specified is not yet implemented.

A full-featured Raku compiler must not throw such exceptions, but still provide the X::NYI class for compatibility reasons.

A typical error message is

HyperWhatever is not yet implemented. Sorry.


method new§

method new:$feature:$did-you-mean:$workaround)

This is the default constructor for X:NYI which can take three parameters with obvious meanings.

class Nothing {
    method ventured$sub**@args{
        X::NYI.newfeature => &?,
                    did-you-mean => "gained",
                    workaround => "Implement it yourself" ).throw;
my $nothing =;

In this case, we are throwing an exception that indicates that the ventured routine has not been implemented; we use the generic &? to not tie the exception to the method name in case it is changed later on. This code effectively throws this exception

# ventured not yet implemented. Sorry. 
# Did you mean: gained? 
# Workaround: Implement it yourself 
#   in method ventured at NYI.raku line 6 
#   in block <unit> at NYI.raku line 14 

Using the exception properties, it composes the message that we see there.

method feature§

Returns a Str describing the missing feature.

method did-you-mean§

Returns a Str indicating the optional feature that is already implemented.

method workaround§

It helpfully shows a possible workaround for the missing feature, if it's been declared.

method message§

Returns the message including the above properties.