{
Semantic routines for the Yacc parser.
Copyright (c) 1990-92 Albert Graef <ag@muwiinfa.geschichte.uni-mainz.de>
Copyright (C) 1996 Berend de Boer <berend@pobox.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
$Revision: 1.2 $
$Modtime: 96-08-01 6:03 $
$History: YACCSEM.PAS $
*
* ***************** Version 2 *****************
* User: Berend Date: 96-10-10 Time: 21:16
* Updated in $/Lex and Yacc/tply
* Updated for protected mode, windows and Delphi 1.X and 2.X.
}
unit YaccSem;
interface
var
act_prec : Integer;
(* active precedence level in token and precedence declarations (0 in
%token declaration) *)
act_type : Integer;
(* active type tag in token, precedence and type declarations *)
procedure yyerror ( msg : String );
(* YaccLib.yyerror redefined to ignore 'syntax error' message; the parser
does its own error handling *)
function sym ( k : Integer ) : Integer;
(* returns internal symbol number for the symbol k; if k is yet undefined,
a new nonterminal or literal symbol is created, according to the
appearance of symbol k (nonterminal if an ordinary identifier, literal
otherwise) *)
function ntsym ( k : Integer ) : Integer;
(* like sym, but requires symbol k to be a nonterminal symbol; if it
is already defined a literal, an error message is issued, and a dummy
nonterminal symbol returned *)
function litsym ( k : Integer; n : Integer ) : Integer;
(* same for literal symbols; if n>0 it denotes the literal number to be
assigned to the symbol; when a new literal identifier is defined, a
corresponding constant definition is also written to the definition
file *)
procedure next_section;
(* find next section mark (%%) in code template *)
procedure definitions;
(* if necessary, write out definition of the semantic value type YYSType *)
procedure copy_code;
(* copy Turbo Pascal code section ( %{ ... %} ) to output file *)
procedure copy_action;
(* copy an action to the output file *)
procedure copy_single_action;
(* like copy_action, but action must be single statement terminated
with `;' *)
procedure copy_rest_of_file;
(* copies the rest of the source file to the output file *)
procedure start_rule ( sym : Integer );
(* start a new rule with lhs nonterminal symbol sym *)
procedure start_body;
(* start a new rule body (rhs) *)
procedure end_body;
(* end a rule body *)
procedure add_symbol ( sym : Integer );
(* add the denoted symbol to the current rule body *)
procedure add_action;
(* add an action to the current rule body *)
procedure add_rule_prec ( sym : Integer );
(* add the precedence of terminal symbol sym to the current rule *)
procedure generate_parser;
(* generate the parse table *)
implementation
uses YaccBase, YaccTabl, YaccClos, YaccLR0, YaccLook,
YaccPars, YaccMsgs;
procedure yyerror ( msg : String );
begin
if msg='syntax error' then
(* ignore *)
else
fatal(msg)
end(*yyerror*);
function act_char : char;
begin
if cno>length(line) then
if eof(yyin) then
act_char := #0
else
act_char := nl
else
act_char := line[cno]
end(*act_char*);
function lookahead_char : char;
begin
if succ(cno)>length(line) then
if eof(yyin) then
lookahead_char := #0
else
lookahead_char := nl
else
lookahead_char := line[succ(cno)]
end(*lookahead_char*);
procedure next_char;
begin
if cno>length(line) then
if eof(yyin) then
{ nop }
else
begin
readln(yyin, line);
inc(lno); cno := 1
end
else
inc(cno)
end(*next_char*);
var
(* Current rule: *)
act_rule : RuleRec;
(* Actions: *)
n_act : Integer;
p_act : Boolean;
function sym ( k : Integer ) : Integer;
var s : Integer;
begin
if is_def_key(k, s) then
sym := s
else if sym_table^[k].pname^[1]='''' then
begin
s := new_lit;
def_key(k, s);
sym := s;
end
else
begin
s := new_nt;
def_key(k, s);
sym := s;
end
end(*sym*);
function ntsym ( k : Integer ) : Integer;
var s : Integer;
begin
if is_def_key(k, s) then
if s<0 then
ntsym := s
else
begin
error(nonterm_expected);
ntsym := -1;
end
else if sym_table^[k].pname^[1]='''' then
begin
error(nonterm_expected);
ntsym := -1;
end
else
begin
s := new_nt;
def_key(k, s);
ntsym := s;
end
end(*ntsym*);
function litsym ( k : Integer; n : Integer ) : Integer;
var s : Integer;
begin
if is_def_key(k, s) then
if s>=0 then
begin
if n>0 then error(double_tokennum_def);
litsym := s;
end
else
begin
error(literal_expected);
litsym := 1;
end
else if sym_table^[k].pname^[1]='''' then
begin
if n>0 then
begin
add_lit(n);
s := n;
end
else
s := new_lit;
def_key(k, s);
litsym := s;
end
else
begin
if n>0 then
begin
add_lit(n);
s := n;
end
else
s := new_lit;
def_key(k, s);
writeln(yyout, 'const ', pname(s), ' = ', s, ';');
litsym := s;
end;
end(*litsym*);
procedure next_section;
var line : String;
begin
while not eof(yycod) do
begin
readln(yycod, line);
if line='%%' then exit;
writeln(yyout, line);
end;
end(*next_section*);
procedure definitions;
var i : Integer;
begin
if n_types>0 then
begin
writeln(yyout);
writeln(yyout, 'type YYSType = record case Integer of');
for i := 1 to n_types do
writeln(yyout, ' ':15, i:3, ' : ( ',
'yy', sym_table^[type_table^[i]].pname^, ' : ',
sym_table^[type_table^[i]].pname^, ' );');
writeln(yyout, ' ':15, 'end(*YYSType*);');
end;
end(*definitions*);
procedure copy_code;
var str_state : Boolean;
begin
str_state := false;
while act_char<>#0 do
if act_char=nl then
begin
writeln(yyout);
next_char;
end
else if act_char='''' then
begin
write(yyout, '''');
str_state := not str_state;
next_char;
end
else if not str_state and (act_char='%') and (lookahead_char='}') then
exit
else
begin
write(yyout, act_char);
next_char;
end;
end(*copy_code*);
procedure scan_val;
(* process a $ value in an action
(not very pretty, but it does its job) *)
var tag, numstr : String; i, code : Integer;
begin
tokleng := 0;
next_char;
if act_char='<' then
begin
(* process type tag: *)
next_char;
tag := '';
while (act_char<>nl) and (act_char<>#0) and (act_char<>'>') do
begin
tag := tag+act_char;
next_char;
end;
if act_char='>' then
begin
if not search_type(tag) then
begin
tokleng := length(tag);
error(unknown_identifier);
end;
next_char;
end
else
error(syntax_error);
end
else
tag := '';
tokleng := 0;
if act_char='$' then
begin
(* left-hand side value: *)
write(yyout, 'yyval');
(* check for value type: *)
if (tag='') and (n_types>0) then with act_rule do
if sym_type^[lhs_sym]>0 then
tag := sym_table^[sym_type^[lhs_sym]].pname^
else
begin
tokleng := 1;
error(type_error);
end;
if tag<>'' then write(yyout, '.yy', tag);
next_char;
end
else
begin
(* right-hand side value: *)
if act_char='-' then
begin
numstr := '-';
next_char;
end
else
numstr := '';
while ('0'<=act_char) and (act_char<='9') do
begin
numstr := numstr+act_char;
next_char;
end;
if numstr<>'' then
begin
val(numstr, i, code);
if code=0 then
if i<=act_rule.rhs_len then
begin
write(yyout, 'yyv[yysp-', act_rule.rhs_len-i, ']');
(* check for value type: *)
if (tag='') and (n_types>0) then with act_rule do
if i<=0 then
begin
tokleng := length(numstr)+1;
error(type_error);
end
else if sym_type^[rhs_sym[i]]>0 then
tag := sym_table^[sym_type^[rhs_sym[i]]].pname^
else
begin
tokleng := length(numstr)+1;
error(type_error);
end;
if tag<>'' then write(yyout, '.yy', tag);
end
else
begin
tokleng := length(numstr);
error(range_error);
end
else
error(syntax_error)
end
else
error(syntax_error)
end
end(*scan_val*);
procedure copy_action;
var str_state : Boolean;
begin
str_state := false;
while act_char=' ' do next_char;
write(yyout, ' ':9);
while act_char<>#0 do
if act_char=nl then
begin
writeln(yyout);
next_char;
while act_char=' ' do next_char;
write(yyout, ' ':9);
end
else if act_char='''' then
begin
write(yyout, '''');
str_state := not str_state;
next_char;
end
else if not str_state and (act_char='}') then
begin
writeln(yyout);
exit;
end
else if not str_state and (act_char='$') then
scan_val
else
begin
write(yyout, act_char);
next_char;
end;
end(*copy_action*);
procedure copy_single_action;
var str_state : Boolean;
begin
str_state := false;
while act_char=' ' do next_char;
write(yyout, ' ':9);
while act_char<>#0 do
if act_char=nl then
begin
writeln(yyout);
next_char;
while act_char=' ' do next_char;
write(yyout, ' ':9);
end
else if act_char='''' then
begin
write(yyout, '''');
str_state := not str_state;
next_char;
end
else if not str_state and (act_char=';') then
begin
writeln(yyout, ';');
exit;
end
else if not str_state and (act_char='$') then
scan_val
else
begin
write(yyout, act_char);
next_char;
end;
end(*copy_single_action*);
procedure copy_rest_of_file;
begin
while act_char<>#0 do
if act_char=nl then
begin
writeln(yyout);
next_char;
end
else
begin
write(yyout, act_char);
next_char;
end;
end(*copy_rest_of_file*);
procedure start_rule ( sym : Integer );
begin
if n_rules=0 then
begin
(* fix start nonterminal of the grammar: *)
if startnt=0 then startnt := sym;
(* add augmented start production: *)
with act_rule do
begin
lhs_sym := -1;
rhs_len := 2;
rhs_sym[1] := startnt;
rhs_sym[2] := 0; (* end marker *)
end;
add_rule(newRuleRec(act_rule));
end;
act_rule.lhs_sym := sym;
end(*start_rule*);
procedure start_body;
begin
act_rule.rhs_len := 0;
p_act := false;
writeln(yyout, n_rules:4, ' : begin');
end(*start_body*);
procedure end_body;
begin
if not p_act and (act_rule.rhs_len>0) then
(* add default action: *)
writeln(yyout, ' ':9, 'yyval := yyv[yysp-',
act_rule.rhs_len-1, '];');
add_rule(newRuleRec(act_rule));
writeln(yyout, ' ':7, 'end;');
end(*end_body*);
procedure add_rule_action;
(* process an action inside a rule *)
var k : Integer; r : RuleRec;
begin
writeln(yyout, ' ':7, 'end;');
inc(n_act);
k := get_key('$$'+intStr(n_act));
with r do
begin
lhs_sym := new_nt;
def_key(k, lhs_sym);
rhs_len := 0;
end;
with act_rule do
begin
inc(rhs_len);
if rhs_len>max_rule_len then fatal(rule_table_overflow);
rhs_sym[rhs_len] := r.lhs_sym;
end;
add_rule(newRuleRec(r));
rule_prec^[n_rules+1] := rule_prec^[n_rules];
rule_prec^[n_rules] := 0;
writeln(yyout, n_rules:4, ' : begin');
end(*add_rule_action*);
procedure add_symbol ( sym : Integer );
begin
if p_act then add_rule_action;
p_act := false;
with act_rule do
begin
inc(rhs_len);
if rhs_len>max_rule_len then fatal(rule_table_overflow);
rhs_sym[rhs_len] := sym;
if sym>=0 then rule_prec^[n_rules+1] := sym_prec^[sym]
end
end(*add_symbol*);
procedure add_action;
begin
if p_act then add_rule_action;
p_act := true;
end(*add_action*);
procedure add_rule_prec ( sym : Integer );
begin
rule_prec^[n_rules+1] := sym_prec^[sym];
end(*add_rule_prec*);
procedure generate_parser;
begin
if startnt=0 then error(empty_grammar);
if errors=0 then
begin
write('sort ... ');
sort_rules; rule_offsets;
write('closures ... ');
closures;
write('first sets ... ');
first_sets;
write('LR0 set ... ');
LR0Set;
write('lookaheads ... ');
lookaheads;
writeln;
write('code generation ... ');
parse_table;
end;
end(*generate_parser*);
begin
n_act := 0;
end(*YaccSem*).
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