One caching strategy is to retain the X most-recently-referenced items and discard any additional items. In "high performance" MRU-list ... , comp.lang.tcl, 2015-01-21, Christian Gollwitzer suggests an implementation of most-recently used that takes advantage of the order-preserving operation of dicts. Here is the suggestion, slightly modified to be more general:
proc pushmru {name limit args} {
upvar $name dict
foreach key $args {
dict unset dict $key
dict set dict $key {}
while {[dict size $dict] > $limit} {
dict unset dict [lindex [dict keys $dict] 0]
}
}
return $dict
}Example
set i 0
while {[incr i] < 20} {
pushmru cache 4 key$i
}