# vim:fileencoding=utf-8:foldmethod=marker

Program <- skip (Function _endline*)+ eof

# *** variable definition *** {{{

Variable <- IDENTIFIER Definition
		  / return_keyword " is " value

Definition <- " is " (value / "a " type)

value <- IDENTIFIER 
	   / number


type <- "number"

# }}}

fn_keyword <- "how-to"

argouments_keyword <- "requires"

return_keyword <- "resoult"

function_keywords <- fn_keyword / argouments_keyword / return_keyword

Function <- 
		  fn_keyword " " IDENTIFIER ":" newline
		  Requires endline
		  Resoult endline
		  (Step endline)+

Requires <- argouments_keyword " " Argouments

Argouments <- "nothing"
			/ "a " type " " IDENTIFIER (" and a " type " " IDENTIFIER)*

Resoult <- return_keyword " is " ("nothing" / "a " type)

Fn_call <- IDENTIFIER " " (value (" and " value)*)? (steps_keyword " " number"-"number (" and " number"-"number)*)?

if_keyword <- "if"

If_call <- if_keyword " " value ((" and " value)* " are " / " is ") operation " " (Fn_call / Variable)

operation <- "equal"
		   / "different"
		   / "true"
		   / "false"

if_keywords <- if_keyword / operation

repeat_keyword <- "repeat"

step_keyword <- "step" # single step

steps_keyword <- "steps" # multiple steps

relative_keyword <- "from" # from x step to the end/current positionx

relative_position <- "the start"

relative_numbering_keyword <- "steps ago"

relative_numbering <- number " " relative_numbering_keyword

Repeat_call <- repeat_keyword " " (
			     step_keyword " " number
			   / steps_keyword " " number"-"number ("and" number"-"number)*
			   / relative_keyword " " (
				relative_position  
				  / relative_numbering
				  / step_keyword " " number
				  )
			   ) (" with " value (" and " value)*)?

repeat_call_keywords <- repeat_keyword 
					  / step_keyword 
					  / steps_keyword 
					  / relative_keyword 
					  / relative_position 
					  / relative_numbering_keyword 

Step <- number") "
	  (Variable
	   / If_call
	   / Repeat_call
	   / Fn_call) endline

IDENTIFIER <- !keyword [A-Za-z] [A-Za-z0-9_]*

generic_keywords <- "a "
				  / "is "
				  / "and "
				  / "nothing "
				  keyword <- function_keywords / if_keywords / repeat_call_keywords / generic_keywords

comment <- "//" (!newline .)* newline
# *** Nicities *** {{{

skip <- ([ \n] / comment)*

endline <- &. " "* comment? "\n"?
_endline <- &. " "* comment? "\n"

eof <- !.

newline <- "\n"

number <- binary
		/ hex
		/ dec

binary <- "0b" [01]+
		hex <- "0x" [0-9A-Fa-f]+
		dec <- [0-9]+

# }}}