Part 0: Introduction. ********************* Felix has a rather complex expression grammar. It has a limited ability to add new infix operators of a fixed precedence (although the preprocessor directive appears to permit a choice of precedence level).
Now we have the extensible GLR parser available, it is time to consider redesiging the expression grammar. There are several aspects. First, we need to partition the grammar between the compiler and the library. Second, we need to devise a way to specify semantic actions which is better than the large number of hard coded ad hoc terms currently supported in the compiler. I want to begin discussion how we should make the new grammar and extension system look, so please comment! Vent your pet hates and complaints, make constructive and useless suggestions, be prepared for controversy, be willing to make radical suggestions! Part 1. The existing grammar (roughly) expr: | LET pattern EQUAL expr IN expr | rvalue rvalue: | lambda lambda: | dollar_apply | adjectives FUNCTION tvarlist lambda_fun_args opt_type_expr EQUAL compound | adjectives FUNCTION tvarlist lambda_fun_args opt_type_expr EQRIGHTARROW expr | adjectives PROCEDURE tvarlist lambda_fun_args compound | adjectives PROCEDURE tvarlist compound dollar_apply: | tuple UNLESS expr THEN dollar_apply | tuple DOLLAR dollar_apply | tuple tuple: | or_condition tuple_suffix | or_condition tuple_suffix: | COMMA or_condition tuple_suffix | COMMA or_condition typeexpr: or_condition or_condition: | and_condition OR or_list | and_condition and_condition: | not_condition AND and_list | not_condition not_condition: | notop not_condition | comparison comparison: | sum cmp_op sum cmp_item_list | sum cmp_op sum | as_expr as_expr: | as_expr AS NAME | setunion setunion: | user10 VBARVBAR setunion_list | user10 setunion_list: | user10 VBARVBAR setunion_list | user10 user10: | user10 USER10 setintersection | setintersection setintersection: | arrow AMPERAMPER setintersection_list | arrow setintersection_list: | arrow AMPERAMPER setintersection_list | arrow arrow: | case_literal RIGHTARROW arrow | case_literal LONGRIGHTARROW arrow | case_literal case_literal: | CASE INTEGER | CASE INTEGER OF sum | CASE NAME OF sum | bor bor: | bor SLOSHVBAR bxor | bxor bxor: | bxor SLOSHCIRCUMFLEX band | band band: | band SLOSHAMPER shift | shift shift: | shift LEFTSHIFT sum | shift RIGHTSHIFT sum | sum /* sum formation is 'psuedo-associative' */ sum: | subtraction PLUS sum_list | subtraction sum_list: | subtraction PLUS sum_list | subtraction subtraction: | subtraction MINUS product | product /* product formation is 'psuedo-associative' */ product: | term STAR product_list | term /* division is left associative: note higher precedence the product, so that a * b/c * d -> a * (b/c) * d */ term: | term SLASH power | term PERCENT power | prefixed /* note weird recursion here: we need to support -x ** -x = -(x**(-x)) */ prefixed: | LVAL power | EXCLAMATION power | PLUS power | MINUS power | TILDE power | power /* exponentiation is right associative */ power: | superscript STARSTAR prefixed | superscript superscript: | superscript CIRCUMFLEX refr | refr refr: | UNION LBRACE type_sum_items2 RBRACE | STRUCT compound | AMPER refr | STAR refr | DEREF refr | NEW refr | application /* applications is left associative */ application: | application coercion | CASENO coercion | MACRO CTOR NAME coercion | coercion coercion: | coercion COLON factor | suffixed_name | factor factor: | hash_name | factor DOT LSQB expr RSQB | factor DOT LSQB expr TO expr RSQB | factor DOT LSQB expr TO RSQB | factor DOT LSQB TO expr RSQB | factor DOT simple_name_parts | factor DOTRIGHTARROW simple_name_parts | factor DOT LPAR INTEGER RPAR hash_name: | HASH hash_name | the_name the_name: | NOEXPAND qualified_name | THE qualified_name | qualified_name | QUEST NAME | atom qualified_name: | qualified_name COLONCOLON simple_name_parts | simple_name_parts cond: | IF expr THEN expr else_part ENDIF atom: | UNDERSCORE | CALLBACK LSQB qualified_name RSQB | DOTDOTDOT | type_match_expr | expr_code_prefix NAME | expr_code_prefix STRING | LSQBAR expr RSQBAR | LBRACE expr RBRACE | glr_parse | match_expr | regmatch_expr | typecase | compound | LPAR expr RPAR | LPAR RPAR | literal | cond | FSTRING | QSTRING | USERLB expr USERRB literal: | integer_literal | string_literal | float_literal integer_literal: | INTEGER float_literal: | FLOAT string_literal: | STRING | WSTRING | USTRING | CSTRING simple_name_parts: | NAME LSQB expr RSQB | identifier identifier: | NAME suffixed_name: | qualified_name OF factor -- John Skaller <skaller at users dot sf dot net> Felix, successor to C++: http://felix.sf.net ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Felix-language mailing list Felix-language@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/felix-language
