The forget function is used to clear remember tables of procedures.  Its precise action is controlled by the options given, whether f is a procedure or a module, and whether the remember table(s) in question is a pure remember table or a cache table.

The options are:

subfunctions = true or false (default: true)

forgetpermanent = true or false (default: false)

reinitialize = true or false (default: true)

forget(f, a, b, c, ..., opts) restricts the action of forget to clearing only remember table entry(s) indexed by the argument list [a, b, c, ...], and subject to the interpretations implied by the options in opts.

As a special case, specifying f as an empty range allows for selective clearing of remember table entries from all remember tables in the system.  This requires a second argument, to indicate which entries to clear. For example, forget(..,x), which will clear all remembered entries in the system that reference x.  

$\mathrm{forget}\left(\mathrm{evalc}\right)$

$\sin \left(x\right)\;$$\sin \left(\mathrm{\pi }\right)$

$\sin \left(x\right)$

$0$

$\mathrm{op}\left(4\,\mathrm{op}\left(\sin \right)\right)$

$\mathrm{Cache}\left(512\,'\mathrm{temporary}'=\left[-x=-\sin \left(x\right)\,x=\sin \left(x\right)\right]\,'\mathrm{permanent}'=\left[0=0\,\frac{\mathrm{\pi }}{3}=\frac{\sqrt{3}}{2}\,\frac{\mathrm{\pi }}{2}=1\,\frac{\mathrm{\pi }}{6}=\frac{1}{2}\,\mathrm{\infty }=\mathrm{undefined}\,\frac{\mathrm{\pi }}{4}=\frac{\sqrt{2}}{2}\,\mathrm{\pi }=0\,-\mathrm{\infty }=\mathrm{undefined}\,\mathrm{I}=\mathrm{I}\sinh \left(1\right)\right]\right)$

$\mathrm{forget}\left(\sin \,x\,\mathrm{subfunctions}=\mathrm{false}\right)$

$\mathrm{op}\left(4\,\mathrm{op}\left(\sin \right)\right)$

$\mathrm{Cache}\left(512\,'\mathrm{temporary}'=\left[-x=-\sin \left(x\right)\right]\,'\mathrm{permanent}'=\left[0=0\,\frac{\mathrm{\pi }}{3}=\frac{\sqrt{3}}{2}\,\frac{\mathrm{\pi }}{2}=1\,\frac{\mathrm{\pi }}{6}=\frac{1}{2}\,\mathrm{\infty }=\mathrm{undefined}\,\frac{\mathrm{\pi }}{4}=\frac{\sqrt{2}}{2}\,\mathrm{\pi }=0\,-\mathrm{\infty }=\mathrm{undefined}\,\mathrm{I}=\mathrm{I}\sinh \left(1\right)\right]\right)$

$\mathrm{forget}\left(\sin \,\mathrm{subfunctions}=\mathrm{false}\right)$

$\mathrm{op}\left(4\,\mathrm{op}\left(\sin \right)\right)$

$\mathrm{Cache}\left(512\,'\mathrm{permanent}'=\left[0=0\,\frac{\mathrm{\pi }}{3}=\frac{\sqrt{3}}{2}\,\frac{\mathrm{\pi }}{2}=1\,\frac{\mathrm{\pi }}{6}=\frac{1}{2}\,\mathrm{\infty }=\mathrm{undefined}\,\frac{\mathrm{\pi }}{4}=\frac{\sqrt{2}}{2}\,\mathrm{\pi }=0\,-\mathrm{\infty }=\mathrm{undefined}\,\mathrm{I}=\mathrm{I}\sinh \left(1\right)\right]\right)$

$\mathrm{forget}\left(\sin \,\mathrm{forgetpermanent}\,\mathrm{reinitialize}=\mathrm{false}\right)$

$\mathrm{op}\left(4\,\mathrm{op}\left(\sin \right)\right)$

$\mathrm{Cache}\left(512\right)$

$\mathrm{forget}\left(\mathrm{LinearAlgebra}\right)$