xcom­ment – Al­lows se­lected en­vi­ron­ments to be in­cluded/ex­cluded

The pack­age de­fines an en­vi­ron­ment that only type­sets spec­i­fied en­vi­ron­ments within its scope.
So, for ex­am­ple, if you want noth­ing but the fig­ure and ta­ble en­vi­ron­ments in your doc­u­ment, you can en­close the whole doc­u­ment with an xcom­ment en­vi­ron­ment that ex­cludes ev­ery­thing but. This is a lot eas­ier than ex­clud­ing the chunks of text be­tween the en­vi­ron­ments you want, or cre­at­ing an en­tire doc­u­ment con­tain­ing only those en­vi­ron­ments.
The pack­age was pre­vi­ously part of the sem­i­nar bun­dle for type­set­ting pre­sen­ta­tions.