program ::= expressions
ident ::= [a-zA-Z_][a-zA-Z0-9_]*
digit ::= [0-9]
type_defs ::= ident type_def | ident type_def ',' type_defs
type_def ::= ':' ident
expressions ::= expression | expressions expression
expression ::= function_def | extern_def | funcptr_def | struct_def | var_def | if_stmt | for_stmt | while_stmt | expression
function_def ::= ident ':=' 'block' '(' type_defs ')' type_def
extern_def ::= ident ':=' 'extern' '(' type_defs ')' type_def |
               ident ':=' 'extern' '(' ')' type_def
var_def ::= ident ':=' expression
if_stmt ::= 'if' '(' expression ',' expression ',' expression ')' |
            'if' '(' expression ',' expression ')' |
            'if' '(' expression ')' 'then' '(' expression ')' elseif_list 'else' '(' expression ')' |
            'if' '(' expression ')' 'then' '(' expression ')' elseif_list |
            'if' '(' expression ')' 'then' '(' expression ')' 'else' '(' expression ')'
elseif_list ::= elseif_list 'elseif' '(' expression ')' |
                'elseif' '(' expression ')'
for_stmt ::= 'for' '(' ident ',' expression ',' expression ',' expression ')'
while_stmt ::= 'while' '(' expression ',' expression ')'
expression ::= func_call | number_def | string_def | struct_member_access
func_call ::= ident '(' call_argument_list ')' |
              ident '(' ')'
call_argument_list ::= expression | call_argument_list ',' expression
number_def ::= digit+ | digit+ '.' digit+
string_def ::= '"' [^"] any* '"'