IFS Grammar:

"ifs"

["domain" {"(" | "["} expr "," expr {")" | "]"}  
          {"(" | "["} expr "," expr {")" | "]"} ]

[ "polygon" "(" expr "," expr ")" { "(" expr "," expr ")" } ]

[ "transform" op { op } ]

[ "dots" num ]

"order"  num

[ "image"  op { op } ]

===

expr::= [ "+" | "-" ] term { "+" term | "-" term }
term::= factor | { "*" factor | "/" factor }
factor:= prim | { "**" prim }
prim:= num | function "(" expr ")" | "(" expr ")"
function::= "sin"  | "cos"  | "atan" | "log" | "expr"
          | "sinh" | "cosh" | "atanh"

op::= {   "rot" "(" expr ")" | "rfx" | "rfy" | "rfc" 
		| "trl" "(" expr "," expr ")" 
		| "scl" "(" expr[ "," expr] ")"
		| "lin" "(" expr "," expr "," expr "," expr ")" } 

===

[ <x> ] = optional presence of <x>
{ <x> } = zero or more times presence of <x>
"x" = mandatory presence of <x>