tag_system

tag system emulator written in rust

usage

tag systems are defined in JSON. the program accepts as an argument the filename to read the definition in; in the abscence of an argument it'll read the definition from stdin. both of the following are valid:

• cargo run ./examples/collatz
• cat ./examples/collatz | cargo run

input

taken from ./examples/elementary_arithmetic which either adds or subtracts two signed 3 bit integers

{
	"init":"-      3      2      ",
	"token_size": 7,
	"halt_symbol": " ",
	"productions": [
		{"t":"+", "w":"_     "},
		{"t":"-", "w":"_    "},

		{"t":"1", "w":"1[]    "},
		{"t":"[", "w":" Aa   "},
		{"t":"]", "w":"  Ba  "},

		{"t":"A", "w":""},
		{"t":"B", "w":"    _   "},
		{"t":"a", "w":"vwxtsru"},

		{"t":"2", "w":"2{}    "},
		{"t":"{", "w":" Cb   "},
		{"t":"}", "w":"  Db  "},

		{"t":"C", "w":"   _     "},
		{"t":"D", "w":"    _  "},
		{"t":"b", "w":"wxyutsv"},

		{"t":"3", "w":"3<>    "},
		{"t":"<", "w":" Ec   "},
		{"t":">", "w":"  Fc  "},

		{"t":"E", "w":"   _    "},
		{"t":"F", "w":"    _ "},
		{"t":"c", "w":"xyzvutw"},

		{"t":"0", "w":"0()    "},
		{"t":"(", "w":" Gd   "},
		{"t":")", "w":"  Hd  "},

		{"t":"G", "w":"   _    "},
		{"t":"H", "w":"    _"},
		{"t":"d", "w":"uvwsrqt"},

		{"t":"4", "w":"4!@    "},
		{"t":"!", "w":" Ie   "},
		{"t":"@", "w":"  Je  "},

		{"t":"I", "w":"   _   "},
		{"t":"J", "w":"    "},
		{"t":"e", "w":"tuvrqps"},

		{"t":"5", "w":"5#$    "},
		{"t":"#", "w":" Kf   "},
		{"t":"$", "w":"  Lf  "},

		{"t":"K", "w":"   _  "},
		{"t":"L", "w":"    _     "},
		{"t":"f", "w":"stuqpor"},

		{"t":"6", "w":"6%^    "},
		{"t":"%", "w":" Mg   "},
		{"t":"^", "w":"  Ng  "},

		{"t":"M", "w":"   _ "},
		{"t":"N", "w":"    _    "},
		{"t":"g", "w":"rstponq"},

		{"t":"n", "w":" -6"},
		{"t":"o", "w":" -5"},
		{"t":"p", "w":" -4"},
		{"t":"q", "w":" -3"},
		{"t":"r", "w":" -2"},
		{"t":"s", "w":" -1"},
		{"t":"t", "w":" 0"},
		{"t":"u", "w":" 1"},
		{"t":"v", "w":" 2"},
		{"t":"w", "w":" 3"},
		{"t":"x", "w":" 4"},
		{"t":"y", "w":" 5"},
		{"t":"z", "w":" 6"},

		{"t":"_", "w":""}
	]
}

• init: initial word (String)
• token_size: number of symbols to delete each cycle (usize)
• halt_symbol: symbol that will halt execution (char)
• productions: array of production rules
  • t: the symbol to recognize (char)
  • w: word to append when symbol is recognized (String)

note that the initial input to this tag system (./examples/elementary_arithmetic) must conform to the grammar

| operator |         | add / sub this much |        | to / from this|
{+|-}<six characters>{0,1,2,3,4,5,6}<six characters>{0,1,2,3,4,5,6}<six characters>

where 0, 1, 2, and 3 represent themselves, and 4, 5, and 6 represent -1, -2, and -3 respectively.

output

cat ./examples/elementary_arithmetic | cargo run out of the box will yeild

000: -      3      2      
001: 3      2      _    
002: 2      _    3<>    
003: _    3<>    2{}    
004: >    2{}    
005: }      Fc  
006: Fc    Db  
007: b      _ 
008: _ wxyutsv
009: sv
00A:  -1