lset=

[procedure] lset= elt= list1 list2 ...

SRFI-1: Returns true iff every listi is set-equal to listi+1, using elt= for the element-equality procedure. "Set-equal" simply means that listi is a subset of listi+1, and listi+1 is a subset of listi. The elt= procedure's first argument is an element of listi; its second is an element of listi+1.

See also lset<=.