/////////////////////////////////////////////////////////////////////////////
///  Copyright 2013 William R Cooke
///  @file grammar.txt
///  @brief  grammar description for embasic
/////////////////////////////////////////////////////////////////////////////

program   = stlist "END" sublist

stlist    = statement { separator statement} 

sublist   = {sub}

sub       = procedure |
            function  |
            interrupt
            
procedure = "PROCEDURE" ident [ paramaterlist ] [ import ] stlist "END"

function  = "FUNCTION" ident parameterlist [import] stlist "END"

interrupt = "INTERRUPT" ident [import] stlist "END"

statement = assignment |
            declaration |
            if_st |
            proc_st |
            while_st |
	    repeat_st |
	    for_st |
	    case_st |
	    return_st |
	    null_st

assignment = variable "=" exp

declaration = ( "DIM" | "CONSTANT" | "STATIC" | "ROM" | "NONVOLATILE" )  ident [ "(" exp ")" ] 
              [ "AS" ( "BYTE" | "INTEGER" | "WORD" | "LONG" | "SINGLE" | "DOUBLE" | "STRING"]
              [ "AT" exp ]
              
if_st       = "IF" exp "THEN" stlist [ "ELSE" stlist ] "END"

proc_st     = ident [ paramlist]

while_st    = "WHILE" exp "DO" stlist "END"
   
repeat_st   = "REPEAT" stlist "UNTIL" exp

for_st      = "FOR" variable '=' exp "TO" exp ["STEP" exp] stlist "END"
   
case_st     =

return_st   = "RETURN" [ exp ]

null_st     =
   
   
   
exp         = lterm { ("OR" | "XOR") lterm }

lterm       = lfactor { "AND" lfactor }

lfactor     = simpexp { ( "=" | "<>" | "<" | ">" | "<=" | ">=") }

simpexp     = term { ('+' | '-') term }

term        = factor { ("*" | "/" | "MOD") factor }

factor      = literal | constant | variable | funcall |  "(" exp ")" | "-" factor | "NOT" factor

literal     = int | float | char | string

constant    = ident "(" dimlist ")"

variable    = ident "(" dimlist ")"

funcall     = ident "(" parmlist ")"