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Diffstat (limited to 'examples/lox_parser.py')
| -rw-r--r-- | examples/lox_parser.py | 220 |
1 files changed, 0 insertions, 220 deletions
diff --git a/examples/lox_parser.py b/examples/lox_parser.py deleted file mode 100644 index 3b5825a..0000000 --- a/examples/lox_parser.py +++ /dev/null @@ -1,220 +0,0 @@ -""" -The Lox language grammar - -From Robert Nystrom's "Crafting Interpreters" -http://craftinginterpreters.com/ - -The BNF for the Lox language is found at http://craftinginterpreters.com/appendix-i.html -""" -import pyparsing as pp -pp.ParserElement.enable_packrat() - -# punctuation -COMMA, LPAR, RPAR, LBRACE, RBRACE, EQ, SEMI = map(pp.Suppress, ",(){}=;") - -keywords = (CLASS, FUN, VAR, FOR, IF, ELSE, PRINT, RETURN, WHILE, TRUE, FALSE, NIL, THIS, SUPER, AND, OR,) = map( - pp.Keyword, - """class fun var for if else print return while true false nil this super and or""".split() -) -keyword = pp.MatchFirst(keywords) - -identifier = pp.Combine(~keyword + pp.Word(pp.alphas + "_", pp.alphanums + "_'")) -string = pp.QuotedString('"') -number = pp.Regex(r"\d+(\.\d+)?") - -declaration = pp.Forward() -statement = pp.Forward() -class_decl = pp.Forward() -expression = pp.Forward() -block = pp.Forward() - -arguments = pp.delimited_list(expression) -parameters = pp.delimited_list(identifier) -function = identifier + LPAR + pp.Opt(parameters) + RPAR + block -property_ = identifier + block - -fun_decl = FUN + function -var_decl = VAR + identifier + pp.Opt(EQ + expression) + SEMI -class_decl <<= ( - CLASS - - identifier - + pp.Opt("<" + identifier) - + LBRACE - + (function | property_ | class_decl)[...] - + RBRACE -) - - -primary = (TRUE | FALSE | NIL | THIS | number | string | identifier - | SUPER + "." + identifier - # | LPAR + expression + RPAR <-- not needed, infix_notation takes care of this - ) -call = primary + ( - LPAR + pp.Opt(arguments) + RPAR - | "." + identifier -)[1, ...] - -arith_expression = pp.infix_notation( - call | primary, - [ - (pp.one_of("! -"), 1, pp.opAssoc.RIGHT), - (pp.one_of("/ *"), 2, pp.opAssoc.LEFT), - (pp.one_of("- +"), 2, pp.opAssoc.LEFT), - (pp.one_of("> >= < <="), 2, pp.opAssoc.LEFT), - (pp.one_of("!= =="), 2, pp.opAssoc.LEFT), - (AND, 2, pp.opAssoc.LEFT), - (OR, 2, pp.opAssoc.LEFT), - ] -) -assignment = pp.Forward() -assignment <<= (call | identifier) + EQ + (assignment | arith_expression) - -expression <<= assignment ^ arith_expression ^ function - -block <<= pp.Group(LBRACE + declaration[...] + RBRACE) -while_statement = WHILE + LPAR + expression + RPAR + statement -return_statement = RETURN + pp.Opt(expression) + SEMI -print_statement = PRINT + expression + SEMI -if_statement = IF + LPAR + expression + RPAR + statement + pp.Opt(ELSE + statement) -expr_statement = expression + ";" -for_statement = FOR + LPAR + pp.Group( - (var_decl | expr_statement | ";") - + pp.Opt(expression) + ";" - + pp.Opt(expression) -) + RPAR + statement - - -statement <<= pp.Group( - expr_statement - | for_statement - | if_statement - | print_statement - | return_statement - | while_statement - | block -) - -declaration <<= ( - class_decl - | fun_decl - | var_decl - | statement -) - -program = declaration[...] -program.ignore(pp.dbl_slash_comment) - -pp.autoname_elements() -program.create_diagram("lox_program_parser.html", show_groups=True, vertical=3) - - -program.run_tests( - [ - """\ - var a = 1; - { - var a = a + 2; - print a; - } - """, - """\ - { - var i = 0; - while (i < 10) { - print i; - i = i + 1; - } - } - """, - """\ - var a = 0; - var temp; - - for (var b = 1; a < 10000; b = temp + b) { - print a; - temp = a; - a = b; - } - """, - """\ - fun add(a, b, c) { - print a + b + c; - } - - add(1, 2, 3); - """, - """\ - fun count(n) { - while (n < 100) { - if (n == 3) return n; // <-- - print n; - n = n + 1; - } - } - - count(1); - """, - """\ - fun fib(n) { - if (n <= 1) return n; - return fib(n - 2) + fib(n - 1); - } - - for (var i = 0; i < 20; i = i + 1) { - print fib(i); - } - """, - """\ - fun makeCounter() { - var i = 0; - fun count() { - i = i + 1; - print i; - } - - return count; - } - - var counter = makeCounter(); - counter(); // "1". - counter(); // "2". - """, - """\ - fun thrice(fn) { - for (var i = 1; i <= 3; i = i + 1) { - fn(i); - } - } - - thrice(fun (a) { - print a; - }); - // "1". - // "2". - // "3". - """, - """\ - class Math { - square(n) { - return n * n; - } - } - - print Math.square(3); // Prints "9". - """, - """\ - class Circle { - init(radius) { - this.radius = radius; - } - - area { - return 3.141592653 * this.radius * this.radius; - } - } - - var circle = Circle(4); - print circle.area; // Prints roughly "50.2655". - """, - ] -) |