`?T``=..`

`?L`ISO- the functor and arguments of term
`T`comprise the list`L` `append(`

`?A``,`

`?B``,`

`?C``)`

- the list
`C`is the concatenation of lists`A`and`B` `keysort(`

`+L``,`

`-S``)`

- the list
`L`sorted by key yields`S` `length(`

`?L``,`

`?N``)`

- the length of list
`L`is`N` `member(`

`?X``,`

`?L``)`

`X`is a member of`L``memberchk(`

`+X``,`

`+L``)`

`X`is a member of`L``nonmember(`

`+X``,`

`+L``)`

`X`is not a member of`L``sort(`

`+L``,`

`-S``)`

- sorting the list
`L`into order yields`S`

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