command = [ special_command | statement_sequence ] [ jxn_comment ]

special_command = #filespec | #import | #remove | #edit | #reinit | #exit
                | #function | #if | #ifdef | #ifndef | #else if | #else | #endif | #while | #break | #continue | #endwhile | #return | #endfunction   

statement_sequence = statement { ";" statement } [ ";" ]  // trailing ";" supresses result output

jxn_comment = "!" ? random text ?


statement = [ variable_name "=" ] expression | variable_name "="   // "name=" repeats the most recent assignment statement to variable name
            | variable_name ( "+=" | "-=" | "*=" | "/=" | "%=" | "^=" ) expression  // (Wikipedia: → augmented assignment)
            // jxn handles  variable_name op= expression  as a syntactical shortcut of  variable_name = variable_name op ( expression )

            // L-values not (yet) implemented:
            | symbolic_factor_extended "[" expression "]" "=" expression  // workaround: set( symbolic_factor_extended, index_expression, expression ) 
            | symbolic_factor_extended "." field_name     "=" expression  // workaround: set( symbolic_factor_extended, "field_name", expression )


expression = term { ( "+" | "-" ) term }   // left-associative: a op b op c ≡ ( a op b ) op c  ( → Wikipedia: de | en )


term = potenz { ( "*" | "/" ) potenz } | simple_term   // left-associative (like expression)

simple_term = potenz { [ " " /* blank, if necessary */ ] simple_potenz }   // without operator "*" oder "/" (but possibly with sign)
                                                                           // for symbolic_factor_terminated: single argument without () brackets

potenz = { "-" | "+" } simple_potenz

simple_potenz = factor [ ( "^" | "**" ) potenz ]   // without sign for simple_term, (recursive =>) right-associative: a^b^c ≡ a^(b^c)


factor = decimal_constant | symbolic_factor_terminated

decimal_constant = ( digit { digit | "_" } [ "." { digit | "_" } ] | "." { "_" } digit { digit | "_" } ) [ ( "E" | "e" ) [ "-" | "+" ] digit { digit } ]
                   // without sign, no blanks within a decimal_constant, ".2" and "5." are valid, decimal_constant may contain '_'

digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"


symbolic_factor_terminated = "@" [ package_path "." ] class_name [ " " /* blank, if necessary */ ] simple_term   // constructor call ( "@" in JXN ≡ new in Java)
                             | "@" simple_term   // deprecated
                             | [ [ package_path "." ] class_name "." ] static_method_name [ " " /* blank, if necessary */ ] simple_term
                             | symbolic_factor_extended [ "." method_name [ " " /* blank, if necessary */ ] simple_term ]

symbolic_factor_extended = symbolic_factor { "[" [ expression [ ":" [ expression ] ] ] "]"   // []-access, left-associative
                                             | "." field_name | "." method_name argument_list }  // left-associative

symbolic_factor = variable_name | "(" expression ")" | string_constant | character_constant
                  | "{" ( comma_separated_expressions | expression ":" expression ) "}"   // creates an array
                  | "@" [ package_path "." ] class_name argument_list   // constructor call ( "@" in JXN ≡ new in Java)
                  | "@"                                 argument_list   // deprecated
                  |     [ package_path "." ] class_name "." ( static_field_name | static_method_name argument_list )  // static field access or static method call
                  |                                                               static_method_name argument_list    // class defined by first non primitive argument or #import static
                  |                                           static_field_name  // is not supported (=> e.g. E for Math.E is not possible)


variable_name | function_name | parameter_name | class_name | field_name | static_field_name | method_name | static_method_name = identifier

package_path = identifier { "." identifier }

identifier = ? java_identifier_start ? { ? java_identifier_part ? }   // no blanks within an identifier, → isJavaIdentifierStart, → isJavaIdentifierPart


string_constant = """ { character } """  // blanks are significant within a string_constant, "" = empty string

character_constant = "'" character "'"  // without blanks

character = ? single_character ? | "\"" | "\'" | "\\" | "\0" | "\t" | "\n" | "\r" | "\b" | "\f"
            | "\u" hex hex hex hex  // without blanks, Unicode ( → Wikipedia: de | en )
            | "\#" digit { digit } [";"]  // without blanks, Unicode (decimal), ";" may be omitted, if not followed by another digit

hex = digit | "a" | "b" | "c" | "d" | "e" | "f" | "A" | "B" | "C" | "D" | "E" | "F"


argument_list = "(" comma_separated_expressions ")"

comma_separated_expressions = [ expression { "," expression } ]   // may be empty

#filespec.jxn [ argument_list | expression ]  // filespec may contain blanks
#filespec_without_blanks[.jxn] [ argument_list | expression ]
#this [ argument_list | expression ]  // deprecated

#remove variable_name

#import package_path [ "." class_name ]
#remove [ package ] package_path [ "." class_name ]
#remove [ package ] class_name

#import static [ package_path "." ] class_name
#remove static [ package_path "." ] class_name


the following special commands are available

- only for interactive use from the input line:

#edit [ command ]
#reinit
#exit


- only inside a jxn file (not for interactive use):

#function function_name [ "(" [ parameter_name { "," parameter_name } ] ")" ]
#endfunction
#return [ statement ]

#if statement
#ifdef variable_name
#ifndef variable_name
#else [ if statement ]
#endif


- only inside a #function definition (inside a jxn file):

#while statement
#break
#continue
#endwhile