Syntax of X

    :       meaning "is define as"
    |       meaning "or"
    [ ]     square brackets surround optional item
    { }     curly brackets surround repetetive items (zero or more times)
    ( )     round brackets surround alternatives
    ' '     quotes surround one character non-alpha-numeric terminals




    program : {statement}

    statement : command | control_structure | definition

    command : procedure_call | directive

    control_structure : while exp {command | exit} ';'
        | loop exp {command | exit} ';'
        | for user_name exp exp {command | exit} ';'
        | step user_name exp exp exp {command | exit} ';'
        | if exp {command} {elsif exp {command}} [else {command}] ';'
        | using user_name {command} ';'

    definition : procedure_definition | function_definition

    procedure_call : name {exp}

    directive : name {exp}

    exp : variable_call | function_call | literal

    name : built_in_name | user_name

    user_name : first_letter {letter | digit |_|.|!|? }

    variable_call : name | (user_name'['exp']')

    function_call : name {exp}

    literal : number | list | string

    built_in_name : name{name}

    directive : name {exp}

    procedure_definition : command user_name {par} ':' block ';'

    function_definition : function user_name {par}':' block return exp
        {block return exp} ';'

    block : {statement}

    exp : number | literal | list_construct | table_construct | var | function_call

    var : [namespace'.']user_name[':'key]{'[' exp ']'}

    number : ['+'|'-']digit{digit}['.'digit{digit}[['+'|'-']'e'|'E'digit{digit}]]
        | '$'hex_digit{hex_digit}

    digit : '0'...'9'

    hex_digit : digit | 'a'...'f'

    name : alpha | sym {alpha | sym | digit}

    sym : '_'|'+'|'-'|'*'|'/'|'='|'<'|'>'|'?'|'!'|'~'|'%'|'$'|'@'|';'|':'|'`'

Created on September 3, 2001