It's suboptimal that there's no way to get a list of comparisons, without also specifying inputs, e.g.

$ adam compare -list comparisons

Prints the usage help with 'Argument "INPUT1" is required'. ...

It you don't feel like fixing this now, can you open an issue in order to reminder ourselves?

I also think it would be better to break up -list into -list_comparisons -list_aggregators -list_etc since it's impossible from the command-line to introspect all the things you can list.

With args4j, you can just specific a boolean option which doesn't require an operand,e.g.

````
@Args4jOption(required = false, name = "-list_comparisons", usage = "List all the possible comparisons")
var listComparisons: Boolean = false
````