level8.lark

// trying to simply copy level 6 allowing for spaces
// the idea here is:
// allows for almost the same grammar as 6, easy for us
// gives better error messages out of the box
// we check indents in code, we can give better indent errors

start: program
program: _EOL* command (" ")* (_EOL+ command (" ")*)* _EOL* //lines may end on spaces and might be separated by many newlines
?command: print
         | ifs elses?
         | ask
         | for_loop
         | assign_list
         | list_access_var
         | assign  //placing it here means print is will print 'is' and print is Felienne will print 'is Felienne'

//we had to drop invalid, I think because of the if-ifelse, but for now it is pretty ok!!

_EOL: "\r"?"\n"


print : "print " (quoted_text | list_access | var | sum) (" " (quoted_text | list_access | var | sum))*
ask : var " is ask " textwithspaces*
assign_list: var " is " textwithspaces ((", "|",") textwithspaces)+

//TODO: sum needs to be expression here too (like in 7 and up)

assign : var " is " sum | var " is " textwithoutspaces
invalid: textwithoutspaces " " textwithspaces


// new commands for level 4
elses : _EOL (" ")* "else" _EOL (" "+ command) (_EOL " "+ command)* _EOL "end-block"
ifs: "if " condition _EOL (" "+ command) (_EOL " "+ command)* _EOL "end-block" //'if' cannot be used in Python, hence the name of the rule is 'ifs'


condition: (equality_check|in_list_check) (" and " condition)*
list_access_var : var " is " var " at " (index | random)
equality_check: textwithoutspaces " is " textwithoutspaces
in_list_check: textwithoutspaces " in " var

//new for level 6
?sum: product
   | sum " "* "+" " "* product -> addition
   | sum " "* "-" " "* product -> substraction

?product: atom
    | product " "* "*" " "* atom -> multiplication
    | product " "* "/" " "* atom -> division

?atom: NUMBER | var | NAME //TODO: means we cannot assign strings with spaces? would we want that?

//new for level 8
for_loop: "for " (NAME | var) " in " "range " (NUMBER | var) " to " (NUMBER | var) _EOL (" "+ command) (_EOL " "+ command)* _EOL "end-block"

var: NAME -> var
list_access : var " at " (index | random) -> list_access //todo: could be merged with list_access_var?
index : NUMBER
random : "random"

textwithspaces: /([^\n,]+)/ -> text //anything can be parsed except for a newline and a comma for list separators
textwithoutspaces: /([^\n, *+-\/]+)/ -> text //anything can be parsed except for spaces (plus: a newline and a comma for list separators)
//plus in level 6, calculation elements

quoted_text_no_escape: /'([^']*)'/ -> text //simply all between quotes should this be used at earlier levels?
quoted_text: /'((?:[^\\']|\\.)*)'/ -> text //text can be between single quotes, but quotes may be escaped with \



%import common.LETTER   // imports from terminal library
%import common.DIGIT   // imports from terminal library
%import common.WS_INLINE   // imports from terminal library
%import common.NEWLINE   // imports from terminal library
%import common.SIGNED_INT -> NUMBER
%import common.CNAME -> NAME