Filter

A filter is an oscillator used to delete some but not all of the spaceships in a stream. For example, a blocker can delete every second glider in a stream of period 8n + 4, and can also do the same for LWSS streams. Other examples are the middleweight emulator, T-nosed p4 (either of which can be used to delete every second LWSS in a stream of period 4n + 2) and the fountain (which does the same for MWSS streams).

Filters can be used to make guns of high periods. For instance, the period-20 glider gun can be made p40 with a blocker, then p80 with Rich's p16, and even p160 with 68P32.1:

x = 48, y = 33, rule = B3/S23 20b3o2b2o$14b2o8bobo$14bo10bo$4b2ob3ob2obo8b2o$4bo4bo3bo5b2ob2o$5b3o10bo4bo$8bo10bo4bo$5b3o3bo7bo3b2o$5bo2b2o3b3o4bo$6bo5bobo2bo2b2o$3b3o6bo11bo$3bo8bobobobo4bobo9bo3bo$13b2obobo5bo9bobobobo$15b3o9bob3ob2obobob2ob3obo$27bo2b2obobo3bobob2o2bo$31bobo7bobo2$7b2o11b2o$6bobo11bobo$6bo15bo$5b2o9bo5b2o$10bo6bo$2bo6bobo3b3o$bobo6bo$o3bo$bo3bo7bo17bobo7bobo$2bo3bo5bobo12bo2b2obobo3bobob2o2bo$3bo3bo2b2o2b2o11bob3ob2obobob2ob3obo$4bobo3b2ob2o19bobobobo$5bo3b2ob3o20bo3bo$9b3o14bo$10bobo14bo$11b2o12b3o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ MAXGRIDSIZE 9 WIDTH 700 HEIGHT 500 THUMBSIZE 2 ZOOM 12 GPS 20 AUTOSTART KILLGLIDERS ]]

p160 glider gun (click above to open LifeViewer)

List of filters

• Multiple of 4 but not 8, ×2: Blocker
• Multiple of 8 but not 16, ×2: Rich's p16, Charity's p16
• Multiple of 16 but not 32, ×2: 68P32
• Multiple of 32 but not 64, ×2: 51P384
• Multiple of 5 but not 10, ×2: p10 filter
• Multiple of 5 but not 15, ×3: Karel's p15

See also

• Period multiplier
• Sparker

External links

• Filter at the Life Lexicon