Documentation for listop ... assembled from the following types:

language documentation Operators

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(Operators) listop ...

Called the yada, yada, yada operator or stub operator, if it's the only statement in a routine or type, it marks that routine or type as a stub (which is significant in the context of pre-declaring types and composing roles).

If the ... statement is executed, it calls fail, with the default message Stub code executed.