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Cathain (Irish Gaelic for "when", /kəˈhɪnʲ/ "kah-HIN" or /ˈkahənʲ/ "KAH-huhn") is an esolang created by Nurdle. Inspired by languages like Slashes and Thue, its main function is text replacement, however, instead of text, it's actually bits represented as hexidecimal. It also introduces goto-labels and "timelines".


the initial state is ff there are only 3 commands in Cathain:

Caption text
Symbol Description
!(string) Define a goto label
@(string Goto a label
(search) (replace) Replace text with something else

if you try to call a goto label that hasn't been defined then the timeline terminates and returns !!!


In Cathain, there are timelines, every timeline is defined by a list of bits, every bit corresponds to one of the commands in the given script.
if a bit is on, then its corresponding command will be run in its timeline.
if a bit is off, then its corresponding command will be ignored.
This does include commands that define a label, if a label isn't declared then the timeline will terminate if it tries to call said label.


Example Program

This program is used to show how the timeline system works:

ff 0f
f  a


timeline 0 (00)
  0  FF
  1  FF
       hex: 0xFF 
    string: 'ÿ'
timeline 1 (01)
  0  FF
  1  AA
       hex: 0xAA 
    string: 'ª'
timeline 2 (10)
  0  0F
  1  0F
       hex: 0x0F 
    string: '\x0f'
timeline 3 (11)
  0  0F
  1  0A
       hex: 0x0A 
    string: '\n'

Computational Class

Cathain is widely believed to not be Turing Complete, however its Completeness is unknown. It is at least as powerful as a Finite State machine.

See Also

  • Arís - another language that uses time as a core mechanic of the language.

External Resources