# Parsodus - A language agnostic parser generator
# Copyright © 2016-2017 Thomas Avé, Robin Jadoul, Kobe Wullaert
# 
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# a copy of this software and associated documentation files (the "Software"),
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# 
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parser: LALR(1)
lexesis: calcLexer.lxs
precedence:
    right "EXPONENT"
    left "TIMES" "DIVIDE"
    left "PLUS" "MINUS"
    nonassoc "LT"

start: <start>
grammar:
    <start> ::= <toplevel> <start> [toplevel]
              |                    [toplevel]
              ;

    <toplevel> ::= <toplevel_expr> "SEMICOLON"        [toplevel]
                 | <toplevel_functiondef> "SEMICOLON" [toplevel]
                 | <toplevel_assign> "SEMICOLON"      [toplevel]
                 | <toplevel_error> "SEMICOLON"       [toplevel]
              ;

    <toplevel_expr> ::= <expr>     [toplevel];
    <toplevel_functiondef> ::= <functiondef> [toplevel];
    <toplevel_assign> ::= <assign> [toplevel];
    <toplevel_error> ::= <error>   [toplevel];

    <expr> ::= <expr> "PLUS" <expr>                      [binop]
             | <expr> "MINUS" <expr>                     [binop]
             | <expr> "TIMES" <expr>                     [binop]
             | <expr> "DIVIDE" <expr>                    [binop]
             | <expr> "EXPONENT" <expr>                  [binop]
             | <expr> "LT" <expr>                        [binop]
             | "IDENT"                                   [expr_simple]
             | "NUM"                                     [expr_simple]
             | "MINUS" <expr>                            [umin, right 1]
             | "LPAREN" <expr> "RPAREN"                  [parenthesized]
             | "IDENT" "LPAREN" <opt_arguments> "RPAREN" [functioncall]
             ;

    <opt_arguments> ::= <arguments>     [opt_arguments]
                      |                 [opt_arguments]
                      ;

    <arguments> ::= <expr>                      [arguments]
                  | <arguments> "COMMA" <expr>  [arguments]
                  ;

    <functiondef> ::= "FN" "IDENT" "LPAREN" <opt_idents> "RPAREN" "ARROW" <expr> [functiondef];

    <opt_idents> ::= <idents> [opt_idents]
                   |          [opt_idents]
                   ;

    <idents> ::= "IDENT"                    [idents]
               | <idents> "COMMA" "IDENT"   [idents]
               ;
    
    <assign> ::= "IDENT" "ASSIGN" <expr> [assign];