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 = 90, y = 73, rule = B3/S23 35b2o3b2o$37bobo2bo$34bo5b2o$35bob3o$36b2o2b2o2b2o$28b2o5bo2bobo2bobo$ 27bo2bo4b4o2bobo7b2obo$26bo2bo2bo6bo4bo5bobob3o11b2o$23bo2b3o8b2o2b3ob o3bo2bo4bo9bobo$15bob2o4b3o3b2obo4bo6bo5b3o3bobo4b2o2bo$2o11b3obobo6b 2o3bo7bob3o11bob5o2b4o$obo9bo4bo2bo2b2obo10b5o6b8o6bobo$2bo8bobo3b3o3b o3bo8bobo9bo7b3o4b2ob2o$2b2ob3o4bobo9b3o8b2obo11bo2b2o4bob2o2b2obo$4b 2o8b8o4b2ob2o7b2o9b2o2bo14bo$2b2o4b6o3bo3bo9bo5b2o8bo3b4obo5b6o$bobob 4o2bo3bo3bo7bo6bobo13b3o3bo6bo$bo6bo3b2o2bo2b2o7bob2o3bo10bo6bo2b3o2bo 4b2o$2b6o9b2o2bo16b2o6b2obo3bo4bo2b2o3b2o$6bo5b2o3b2o2bo9bo4bo3bo5b2ob obo2b4o$2b2o4bo3b3o3bo2bo9bo4bo3bo5b2o2b4o$2b2o3b2o3bo3b2o2b2o3bo5bo4b o3bo5b2obobo2b4o$12b4o4bobo14b3o6b2obo3bo4bo2b2o3b2o$16b3ob2o4b4o3b3o 10bo6bo2b3o2bo4b2o$12b4o4bobo27b3o3bo6bo$2b2o3b2o3bo3b2o2b2o3bo5bo5bo 9bo3b4obo5b6o$2b2o4bo3b3o3bo2bo9bo6b2o9b2o2bo14bo$6bo5b2o3b2o2bo10bo4b 2o11bo2b2o4bob2o2b2obo$2b6o9b2o2bo26bo7b3o4b2ob2ob2o$bo6bo3b2o2bo2b2o 8bo2bo15b8o6bobo4bo$bobob4o2bo3bo3bo7b3o2b3o7bo12bob5o2b4obo$2b2o4b6o 3bo3bo6b2o2b2o9b2o5b3o3bobo4b2o2bob2o$4b2o8b8o7bo2bo9b2o5bo2bo4bo9bo$ 2b2ob3o4bobo12bobo2bobo15bobob3o9b2o$2bo8bobo3b3o7b2o4b2o16b2obo$obo9b o4bo2bo55bo3bo$2o11b3obobo51bo3bobobobo3bo$15bob2o20b2o28bo5bobobobo5b o$35b2obo2bob2o22b2o2b2obobo3bobob2o2b2o$35bo4bo2b2o27bobo7bobo$39bo 12bo19bobo7bobo$36bobo14b2o$52b2o2$39b2ob2o3b2ob2o$38bo5bobo5bo$43b2ob 2o$41bo7bo$38bo2bob2ob2obo2bo19bobo7bobo$39bo3bo3bo3bo20bobo7bobo$40b 2ob2ob2ob2o11bo4b2o2b2obobo3bobob2o2b2o$41bo2bobo2bo13b2o4bo5bobobobo 5bo$42bobobobo13b2o7bo3bobobobo3bo$43bo3bo28bo3bo17$82bo$83b2o$82b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ MAXGRIDSIZE 9 WIDTH 800 HEIGHT 700 THUMBSIZE 2 ZOOM 8 GPS 20 AUTOSTART KILLGLIDERS ]]

p160 glider gun (click above to open LifeViewer) RLE: here Plaintext: here

A smaller, more recent period-160 glider gun uses Charity's p16 as the first filter instead:

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 16 THEME Book AUTOSTART KILLGLIDERS ]]

p160 glider gun (click above to open LifeViewer) Catagolue: here

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