pike.git/lib/modules/Parser.pmod/LR.pmod/module.pmod:9e1f00e1eac3ca183f070f8ce488d76abe6c6a9b

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1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 /* * A BNF-grammar in Pike. * Compiles to a LALR(1) state-machine. * * Henrik Grubbström 1996-11-24 */ #pike __REAL_VERSION__ //! LALR(1) parser generator. #pragma strict_types /* * Defines */ /* Errors during parsing */ /* Unexpected EOF */ constant ERROR_EOF= 1; /* Syntax error in input */ constant ERROR_SYNTAX= 2; /* Shift-Reduce or Reduce-Reduce */ constant ERROR_CONFLICTS= 4; /* Action is missing from action object */ constant ERROR_MISSING_ACTION= 8; /* Action is not a function */ constant ERROR_BAD_ACTION_TYPE= 16; /* Action invoked by name, but no object given */ constant ERROR_NO_OBJECT= 32; /* Scanner not set */ constant ERROR_NO_SCANNER= 64; /* Missing definition of nonterminal */ constant ERROR_MISSING_DEFINITION= 128; /* * Classes */ //! //! Specifies the priority and associativity of a rule. //! class Priority { //! Priority value int value; //! Associativity //! //! @int //! @value -1 //! Left //! @value 0 //! None //! @value 1 //! Right //! @endint int assoc; //! Create a new priority object. //! //! @param p //! Priority. //! @param a //! Associativity. void create(int p, int a) { value = p; assoc = a; } } //! //! This object is used to represent a BNF-rule in the LR parser. //! class Rule { //! Non-terminal this rule reduces to. int nonterminal; //! The actual rule array(string|int) symbols; //! Action to do when reducing this rule. //! function - call this function. //! string - call this function by name in the object given to the parser. //! The function is called with arguments corresponding to the values of //! the elements of the rule. The return value of the function will be //! the value of this non-terminal. The default rule is to return the first //! argument. function|string action; /* Variables used when compiling */ //! This rule contains tokens int has_tokens = 0; //! This rule has this many non-nullable symbols at the moment. int num_nonnullables = 0; /* multiset(int) prefix_nonterminals = (<>); multiset(string) prefix_tokens = (<>); */ //! Sequence number of this rule (used for conflict resolving) //! Also used to identify the rule. int number = 0; //! Priority and associativity of this rule. Priority pri; //! Create a BNF rule. //! //! @example //! The rule //! //! rule : nonterminal ":" symbols ";" { add_rule }; //! //! might be created as //! //! rule(4, ({ 9, ":", 5, ";" }), "add_rule"); //! //! where 4 corresponds to the nonterminal "rule", 9 to "nonterminal" //! and 5 to "symbols", and the function "add_rule" is too be called //! when this rule is reduced. //! //! @param nt //! Non-terminal to reduce to. //! @param r //! Symbol sequence that reduces to nt. //! @param a //! Action to do when reducing according to this rule. //! function - Call this function. //! string - Call this function by name in the object given to the parser. //! The function is called with arguments corresponding to the values of //! the elements of the rule. The return value of the function will become //! the value of this non-terminal. The default rule is to return the first //! argument. protected void create(int nt, array(string|int) r, function|string|void a) { mixed symbol; nonterminal = nt; symbols = r; action = a; foreach (r, symbol) { if (stringp(symbol)) { has_tokens = 1; break; } } num_nonnullables = sizeof(r); } } //! Severity level enum SeverityLevel { NOTICE = 0, WARNING, ERROR, }; //! Class handling reporting of errors and warnings. class ErrorHandler { //! Verbosity level //! //! @int //! @value -1 //! Just errors. //! @value 0 //! Errors and warnings. //! @value 1 //! Also notices. //! @endint optional int(-1..1) verbose = 1; protected constant severity_kind = ([ NOTICE:"Notice", WARNING:"Warning", ERROR:"Error" ]); void report(SeverityLevel level, string subsystem, string msg, mixed ... args) { if (level > -verbose) { werror([string(0..255)]("%s: %s: "+msg+"\n"), severity_kind[level], subsystem, @args); } } //! Create a new error handler. //! //! @param verbosity //! Level of verbosity. //! //! @seealso //! @[verbose] protected void create(int(-1..1)|void verbosity) { if (!undefinedp(verbosity)) verbose = verbosity; } } //! This object implements an LALR(1) parser and compiler. //! //! Normal use of this object would be: //! //! @pre{ //! set_error_handler //! {add_rule, set_priority, set_associativity}* //! set_symbol_to_string //! compile //! {parse}* //! @} class Parser { //! The grammar itself. mapping(int : array(Rule)) grammar = ([]); /* Priority table for terminal symbols */ protected mapping(string : Priority) operator_priority = ([]); protected multiset(int|string) nullable = (< >); #if 0 protected mapping(mixed : multiset(Rule)) derives = ([]); /* Maps from symbol to which rules may start with that symbol */ protected mapping(mixed : multiset(Rule)) begins = ([]); #endif /* 0 */ /* Maps from symbol to the rules that use the symbol * (used for finding nullable symbols) */ protected mapping(int : multiset(Rule)) used_by = ([]); //! The initial LR0 state. Kernel start_state; //! Error code int lr_error=0; /* Number of next rule (used only for conflict resolving) */ protected int next_rule_number = 1; //! LR0 states that are already known to the compiler. mapping(string:Kernel) known_states = ([]); //! Compile error and warning handler. function(SeverityLevel, string, string, mixed ...:void) error_handler = ErrorHandler()->report; void report(SeverityLevel level, string subsystem, string msg, mixed ... args) { if (!error_handler) { error_handler = ErrorHandler()->report; } error_handler(level, subsystem, msg, @args); } /* * Sub-classes */ //! //! An LR(0) item, a partially parsed rule. //! protected class Item { //! The rule Rule r; //! How long into the rule the parsing has come. int offset; //! The state we will get if we shift according to this rule Kernel next_state; //! Item representing this one (used for shifts). Item master_item; //! Look-ahead set for this item. multiset(string) direct_lookahead = (<>); //! Look-ahead set used for detecting conflicts multiset(string) error_lookahead = (<>); //! Relation to other items (used when compiling). multiset(Item) relation = (<>); //! Depth counter (used when compiling). int counter; //! Item identification number (used when compiling). int number; //! Used to identify the item. //! Equal to r->number + offset. int item_id; protected string _sprintf() { array(string) res = ({ symbol_to_string(r->nonterminal), ":\t" }); if (offset) { foreach(r->symbols[0..offset-1], int|string symbol) { res += ({ symbol_to_string(symbol), " " }); } } res += ({ "· " }); if (offset != sizeof(r->symbols)) { foreach(r->symbols[offset..], int|string symbol) { res += ({ symbol_to_string(symbol), " " }); } } if (sizeof(indices(direct_lookahead))) { res += ({ "\t{ ", map(indices(direct_lookahead), symbol_to_string) * ", ", " }" }); } return res * ""; } } //! Implements an LR(1) state protected class Kernel { //! Used to check if a rule already has been added when doing closures. multiset(Rule) rules = (<>); //! Contains the items in this state. array(Item) items = ({}); //! Used to lookup items given rule and offset mapping(int:Item) item_id_to_item = ([]); //! Contains the items whose next symbol is this non-terminal. mapping(int : multiset(Item)) symbol_items = ([]); //! The action table for this state //! //! @pre{ //! object(kernel) SHIFT to this state on this symbol. //! object(rule) REDUCE according to this rule on this symbol. //! @} mapping(int|string : Kernel|Rule) action = ([]); //! The symbols that closure has been called on. multiset closure_set = (<>); /* * Functions */ //! Add an item to the state. void add_item(Item i) { int|string symbol; items += ({ i }); item_id_to_item[i->item_id] = i; if (i->offset < sizeof(i->r->symbols)) { symbol = i->r->symbols[i->offset]; if (symbol_items[symbol]) { symbol_items[symbol][i] = 1; } else { symbol_items[symbol] = (< i >); } } } //! Make the closure of this state. //! //! @param nonterminal //! Nonterminal to make the closure on. void closure(int nonterminal) { closure_set[nonterminal] = 1; if (grammar[nonterminal]) { foreach (grammar[nonterminal], Rule r) { if (!rules[r]) { Item new_item = Item(); new_item->r = r; new_item->item_id = r->number; // Not needed, since 0 is the default. // new_item->offset = 0; // rules[r] is set by the post-increment above. rules[r] = 1; add_item(new_item); if (sizeof(r->symbols) && intp(r->symbols[0]) && !closure_set[r->symbols[0]]) { closure([int]r->symbols[0]); } } } } else { report(ERROR, "closure", "Definition missing for non-terminal %s", symbol_to_string(nonterminal)); lr_error |= ERROR_MISSING_DEFINITION; } } //! Make the goto-set of this state. multiset(int|string) goto_set() { multiset(int|string) set = (<>); foreach (items, Item i) { if (i->offset != sizeof(i->r->symbols)) { set[i->r->symbols[i->offset]] = 1; } } report(NOTICE, "goto_set", "=> (< %s >)", map(indices(set), symbol_to_string) * ", "); return set; } //! Generates the state reached when doing goto on the specified symbol. //! i.e. it compiles the LR(0) state. //! //! @param symbol //! Symbol to make goto on. Kernel do_goto(int|string symbol) { multiset(Item) items; report(NOTICE, "do_goto", "Performing GOTO on <%s>", symbol_to_string(symbol)); items = symbol_items[symbol]; if (items) { array(int) item_ids = [array(int)]map(sort(indices(items)->item_id), [function(int,int...:int)]`+, 1); string kernel_hash = sprintf("%@4c", item_ids); Kernel new_state = known_states[kernel_hash]; if (!new_state) { known_states[kernel_hash] = new_state = Kernel(); foreach (indices(items), Item i) { int|string lookahead; Item new_item = Item(); Rule r; int offset = i->offset; new_item->offset = ++offset; new_item->r = r = i->r; new_item->item_id = r->number + offset; new_state->add_item(new_item); if ((offset != sizeof(r->symbols)) && intp(lookahead = r->symbols[offset]) && !new_state->closure_set[lookahead]) { new_state->closure([int]lookahead); } } s_q->push(new_state); } else { // report(NOTICE, "do_goto", "Known state"); } /* DEBUG */ report(NOTICE, "do_goto", "GOTO on %s generated state:\n%s", symbol_to_string(symbol), state_to_string(new_state)); /* !DEBUG */ if (items) { foreach (indices(items), Item i) { i->next_state = new_state; } } } else { report(WARNING, "do_goto", "do_goto() on unknown symbol <%s>", symbol_to_string(symbol)); } } protected string _sprintf() { return sprintf("%{%s\n%}", items); } } //! This is a queue, which keeps the elements even after they are retrieved. protected class StateQueue { //! Index of the head of the queue. int head; //! Index of the tail of the queue. int tail; //! The queue itself. array(Kernel) arr = allocate(64); //! Pushes the state on the queue. //! //! @param state //! State to push. Kernel push(Kernel state) { if (tail == sizeof(arr)) { arr += allocate(tail); } arr[tail++] = state; return state; } //! Return the next state from the queue. Kernel next() { if (head == tail) { return 0; } else { return arr[head++]; } } } /* * Functions */ /* Here are some help functions */ /* Several cast to string functions */ protected string builtin_symbol_to_string(int|string symbol) { if (intp(symbol)) { return "nonterminal"+symbol; } else { return "\"" + symbol + "\""; } } protected function(int|string : string) symbol_to_string = builtin_symbol_to_string; //! Pretty-prints a rule to a string. //! //! @param r //! Rule to print. string rule_to_string(Rule r) { string res = symbol_to_string(r->nonterminal) + ":\t"; if (sizeof(r->symbols)) { foreach (r->symbols, int|string symbol) { res += symbol_to_string(symbol) + " "; } } else { res += "/* empty */"; } return res; } //! Pretty-prints an item to a string. //! //! @param i //! Item to pretty-print. string item_to_string(Item i) { return sprintf("%s", i); } //! Pretty-prints a state to a string. //! //! @param state //! State to pretty-print. string state_to_string(Kernel state) { return sprintf("%s", state); } //! Pretty-prints the current grammar to a string. protected string _sprintf() { array(string) res = ({}); foreach (indices(grammar), int nonterminal) { res += ({ symbol_to_string(nonterminal) }); foreach (grammar[nonterminal], Rule r) { res += ({ "\t: " }); if (sizeof(r->symbols)) { foreach (r->symbols, int|string symbol) { res += ({ symbol_to_string(symbol), " " }); } } else { res += ({ "/* empty */" }); } res += ({ "\n" }); } res += ({ "\n" }); } return res * ""; } string cast_to_string() { return _sprintf(); } //! Implements casting. //! //! @param type //! Type to cast to. protected mixed cast(string type) { if (type == "string") return _sprintf(); return UNDEFINED; } /* Here come the functions that actually do some work */ //! Sets the priority of a terminal. //! //! @param terminal //! Terminal to set the priority for. //! @param pri_val //! Priority; higher = prefer this terminal. void set_priority(string terminal, int pri_val) { Priority pri; if (pri = operator_priority[terminal]) { pri->value = pri_val; } else { operator_priority[terminal] = Priority(pri_val, 0); } } //! Sets the associativity of a terminal. //! //! @param terminal //! Terminal to set the associativity for. //! @param assoc //! Associativity; negative - left, positive - right, //! zero - no associativity. void set_associativity(string terminal, int assoc) { Priority pri; if (pri = operator_priority[terminal]) { pri->assoc = assoc; } else { operator_priority[terminal] = Priority(0, assoc); } } //! Sets the symbol to string conversion function. //! The conversion function is used by the various *_to_string functions //! to make comprehensible output. //! //! @param s_to_s //! Symbol to string conversion function. //! If zero or not specified, use the built-in function. void set_symbol_to_string(void|function(int|string:string) s_to_s) { symbol_to_string = s_to_s || builtin_symbol_to_string; } //! Sets the error report function. //! //! @param handler //! Function to call to report errors and warnings. //! If zero or not specifier, use the built-in function. void set_error_handler(void|function(SeverityLevel, string, string, mixed ...: void) handler) { error_handler = handler || ErrorHandler()->report; } //! Add a rule to the grammar. //! //! @param r //! Rule to add. void add_rule(Rule r) { int|string symbol; /* DEBUG */ report(NOTICE, "add_rule", "Adding rule: %s", rule_to_string(r)); /* !DEBUG */ r->number = next_rule_number; /* Reserve space for the items generatable from this rule. */ next_rule_number += sizeof(r->symbols) + 1; /* First add the rule to the grammar */ if (grammar[r->nonterminal]) { grammar[r->nonterminal] += ({ r }); } else { grammar[r->nonterminal] = ({ r }); } /* Then see if it is nullable */ if (!r->has_tokens) { ADT.Stack new_nullables = ADT.Stack(1024); foreach (r->symbols, symbol) { if (nullable[symbol]) { r->num_nonnullables--; } else { if (used_by[symbol]) { if (used_by[symbol][r]) { /* Only count a symbol once */ r->num_nonnullables--; } else { used_by[symbol][r] = 1; } } else { used_by[symbol] = (< r >); } } } if (!(r->num_nonnullables)) { /* This rule was nullable */ new_nullables->push(r->nonterminal); while (sizeof(new_nullables)) { symbol = [int]new_nullables->pop(); report(NOTICE, "add_rule", "Nulling symbol %s", symbol_to_string(symbol)); nullable[symbol] = 1; if (used_by[symbol]) { foreach (indices(used_by[symbol]), Rule r2) { if (!(--r2->num_nonnullables)) { new_nullables->push(r2->nonterminal); } } used_by[symbol] = 0; /* No more need for this info */ } } } } else { /* Check if it's an operator */ foreach(r->symbols, symbol) { if (operator_priority[symbol]) { r->pri = operator_priority[symbol]; } } } /* The info calculated from this point is not at the moment used * by the compiler */ #if 0 /* Now check for symbols that may begin this rule */ foreach (r->symbols, symbol) { if (!stringp(symbol)) { multiset set = begins[symbol]; r->prefix_nonterminals |= (< symbol >); if (set) { set[r] = 1; } else { begins[symbol] = (< r >); } if (grammar[symbol]) { foreach (grammar[symbol], Rule r2) { r->prefix_nonterminals |= r2->prefix_nonterminals; r->prefix_tokens |= r2->prefix_tokens; foreach (indices(r2->prefix_nonterminals), mixed s2) { set = begins[s2]; if (set) { set[r] = 1; } else { begins[s2] = (< r >); } } } } if (!nullable[symbol]) { break; } } else { r->prefix_tokens[symbol] = 1; break; } } /* Scan through the rules beginning with this rule's non-terminal */ if (begins[r->nonterminal]) { foreach (indices(begins[r->nonterminal]), Rule r2) { r2->prefix_nonterminals |= r->prefix_nonterminals; r2->prefix_tokens |= r->prefix_tokens; /* NOTE: Might want to move values(r->prefixes) out of the loop */ foreach (values(r->prefix_nonterminals), symbol) { multiset set = begins[symbol]; if (set) { set[r2] = 1; } else { begins[symbol] = (< r2 >); } } } } #endif /* 0 */ } /* Here come the functions used by the compiler */ protected Kernel first_state() { Kernel state = Kernel(); array(int) first_state_item_ids = sort(grammar[0]->number); string kernel_hash = sprintf("%@4c", first_state_item_ids); known_states[kernel_hash] = state; foreach (grammar[0], Rule r) { if (!state->rules[r]) { Item i = Item(); i->r = r; // Not needed since 0 is the default. // i->offset = 0; i->item_id = r->number; state->add_item(i); state->rules[r] = 1; /* Since this is an item with offset 0 */ if ((sizeof(r->symbols)) && (intp(r->symbols[0]))) { state->closure([int]r->symbols[0]); } } } return state; } //! Contains all states used. //! In the queue section are the states that remain to be compiled. StateQueue s_q; protected ADT.Stack item_stack; protected void traverse_items(Item i, function(int:void) conflict_func) { int depth; item_stack->push(i); i->counter = depth = sizeof(item_stack); foreach (indices(i->relation), Item i2) { if (!i2->counter) { traverse_items(i2, conflict_func); } if (i->counter > i2->counter) { i->counter = i2->counter; } i->direct_lookahead |= i2->direct_lookahead; } if (i->number == depth) { int cyclic = 0; int empty_cycle = 1; Item i2; while ((i2 = [object(Item)]item_stack->pop()) != i) { i2->number = 0x7fffffff; i2->direct_lookahead = i->direct_lookahead; cyclic = 1; empty_cycle &= !(sizeof(i2->error_lookahead)); } i->count = 0x7fffffff; if (cyclic) { report(NOTICE, "traverse_items", "Cyclic item\n%s", item_to_string(i)); conflict_func(empty_cycle && !(sizeof(i->error_lookahead))); } } } protected void shift_conflict(int empty) { empty; /* Ignored */ } protected void handle_shift_conflicts() { item_stack = ADT.Stack(131072); /* Initialize the counter */ for (int index = 0; index < s_q->tail; index++) { foreach (s_q->arr[index]->items, Item i) { if ((i->offset != sizeof(i->r->symbols)) && (intp(i->r->symbols[i->offset])) && (!i->master_item)) { /* Nonterminal master item */ i->counter = 0; } else { i->counter = 0x7fffffff; } } } for (int index = 0; index < s_q->tail; index++) { foreach (s_q->arr[index]->items, Item i) { if (!i->number) { traverse_items(i, shift_conflict); } } } } protected void follow_conflict(int empty) { empty; /* Ignored */ } protected void handle_follow_conflicts() { item_stack = ADT.Stack(131072); /* Initialize the counter */ for (int index = 0; index < s_q->tail; index++) { foreach (s_q->arr[index]->items, Item i) { if ((i->offset != sizeof(i->r->symbols)) && (intp(i->r->symbols[i->offset])) && (!i->master_item)) { /* Nonterminal master item */ i->counter = 0; } else { i->counter = 0x7fffffff; } } } for (int index = 0; index < s_q->tail; index++) { foreach (s_q->arr[index]->items, Item i) { if (!i->number) { traverse_items(i, follow_conflict); } } } } protected int go_through(Kernel state, int item_id, Item current_item) { Item i, master; i = state->item_id_to_item[item_id]; /* What to do if not found? */ if (!i) { report(ERROR, "go_through", "Item %d not found in state\n" "%s\n" "Backtrace:\n%s", item_id, state_to_string(state), describe_backtrace(backtrace())); return 0; } if (i->master_item) { master = i->master_item; } else { master = i; } if (i->offset < sizeof(i->r->symbols)) { if (go_through(i->next_state, item_id + 1, current_item)) { /* Nullable */ if ((master->offset < sizeof(master->r->symbols)) && (intp(master->r->symbols[master->offset]))) { /* Don't include ourselves */ if (master != current_item) { master->relation[current_item] = 1; } } return nullable[i->r->symbols[i->offset]]; } else return 0; /* Not nullable */ } else { /* At end of rule */ master->relation[current_item] = 1; return 1; /* Always nullable */ } } protected int repair(Kernel state, multiset(int|string) conflicts) { multiset(int|string) conflict_set = (<>); report(NOTICE, "repair", "Repairing conflict in state:\n%s\n" "Conflicts on (< %s >)", state_to_string(state), map(indices(conflicts), symbol_to_string) * ", "); foreach (indices(conflicts), int|string symbol) { int reduce_count = 0; int shift_count = 0; int only_operators = 1; Priority shift_pri, reduce_pri, pri; Rule min_rule = 0; /* Analyse the items */ /* This loses if there are reduce-reduce conflicts, * or shift-shift conflicts */ foreach (state->items, Item i) { if (i->offset == sizeof(i->r->symbols)) { if (i->direct_lookahead[symbol]) { /* Reduction */ reduce_count++; if (pri = i->r->pri) { if (!reduce_pri || (pri->value > reduce_pri->value)) { reduce_pri = pri; } } else { only_operators = 0; } if ((!min_rule) || (i->r->number < min_rule->number)) { min_rule = i->r; } } } else if (!intp(i->r->symbols[i->offset])) { if (i->r->symbols[i->offset] == symbol) { /* Shift */ shift_count++; if (operator_priority[symbol]) { shift_pri = operator_priority[symbol]; } else { only_operators = 0; } } } } int reduce_rest = 0; int shift_rest = 0; if (only_operators) { if (reduce_pri->value > shift_pri->value) { pri = reduce_pri; } else { pri = shift_pri; } foreach (state->items, Item i) { if (i->offset == sizeof(i->r->symbols)) { /* Reduce */ if (i->direct_lookahead[symbol]) { Priority new_pri; if ((new_pri = i->r->pri)->value < pri->value) { report(NOTICE, "repair", "Ignoring reduction of item\n%s\n" "on lookahead %s (Priority %d < %d)", item_to_string(i), symbol_to_string(symbol), new_pri->value, pri->value); i->direct_lookahead[symbol] = 0; if (!sizeof(indices(i->direct_lookahead))) { i->direct_lookahead = (<>); } } else if ((pri->assoc >= 0) && (shift_pri->value == pri->value)) { report(NOTICE, "repair", "Ignoring reduction of item\n%s\n" "on lookahead %s (Right associative)", item_to_string(i), symbol_to_string(symbol)); i->direct_lookahead[symbol] = 0; if (!sizeof(indices(i->direct_lookahead))) { i->direct_lookahead = (<>); } } else { report(NOTICE, "repair", "Kept item\n%s\n" "on lookahead %s", item_to_string(i), symbol_to_string(symbol)); reduce_rest++; } } } else if (i->r->symbols[i->offset] == symbol) { /* Shift */ if (shift_pri->value < pri->value) { report(NOTICE, "repair", "Ignoring shift on item\n%s\n" "on lookahead %s (Priority %d < %d)", item_to_string(i), symbol_to_string(symbol), i->r->pri->value, pri->value); i->direct_lookahead = (<>); i->next_state = 0; } else if ((pri->assoc <= 0) && (reduce_pri->value == pri->value)) { report(NOTICE, "repair", "Ignoring shift on item\n%s\n" "on lookahead %s (Left associative)", item_to_string(i), symbol_to_string(symbol)); i->direct_lookahead = (<>); i->next_state = 0; } else { report(NOTICE, "repair", "Kept item\n%s\n" "on lookahead %s", item_to_string(i), symbol_to_string(symbol)); shift_rest++; } } } } else { /* Not only operators */ if (shift_count) { /* Prefer shifts */ foreach (state->items, Item i) { if (i->offset == sizeof(i->r->symbols)) { /* Reduction */ if (i->direct_lookahead[symbol]) { report(NOTICE, "repair", "Ignoring reduction on item\n%s\n" "on lookahead %s (can shift)", item_to_string(i), symbol_to_string(symbol)); i->direct_lookahead[symbol] = 0; if (!sizeof(indices(i->direct_lookahead))) { i->direct_lookahead = (<>); } } } else { /* Shift */ if (i->r->symbols[i->offset] == symbol) { report(NOTICE, "repair", "Kept item\n%s\n" "on lookahead (shift)%s", item_to_string(i), symbol_to_string(symbol)); shift_rest++; } } } } else { /* Select the first reduction */ foreach (state->items, Item i) { if (i->r == min_rule) { report(NOTICE, "repair", "Kept item\n%s\n" "on lookahead %s (first rule)", item_to_string(i), symbol_to_string(symbol)); reduce_rest++; } else { report(NOTICE, "repair", "Ignoring reduction on item\n%s\n" "on lookahead %s (not first rule)", item_to_string(i), symbol_to_string(symbol)); i->direct_lookahead[symbol] = 0; if (!sizeof(indices(i->direct_lookahead))) { i->direct_lookahead = (<>); } } } } } int conflict_free = 0; if (reduce_rest > 1) { if (shift_rest) { report(ERROR, "repair", "Shift-Reduce-Reduce conflict on lookahead %s", symbol_to_string(symbol)); } else { report(ERROR, "repair", "Reduce-Reduce conflict on lookahead %s", symbol_to_string(symbol)); } } else if (reduce_rest) { if (shift_rest) { report(ERROR, "repair", "Shift-Reduce conflict on lookahead %s", symbol_to_string(symbol)); } else { /* REDUCE * * No other rule left -- conflict resolved! */ conflict_free = 1; } } else { /* SHIFT * * All reductions removed -- conflict resolved! */ conflict_free = 1; } if (conflict_free) { if (reduce_count > 1) { if (shift_count) { report(only_operators?NOTICE:WARNING, "repair", "Repaired Shift-Reduce-Reduce conflict on %s", symbol_to_string(symbol)); } else { report(only_operators?NOTICE:WARNING, "repair", "Repaired Reduce-Reduce conflict on %s", symbol_to_string(symbol)); } } else if (reduce_count) { if (shift_count) { report(only_operators?NOTICE:WARNING, "repair", "Repaired Shift-Reduce conflict on %s", symbol_to_string(symbol)); } else { /* No conflict */ report(NOTICE, "repair", "No conflict on symbol %s (Plain REDUCE)", symbol_to_string(symbol)); } } else { /* No conflict */ report(NOTICE, "repair", "No conflict on symbol %s (SHIFT)", symbol_to_string(symbol)); } } else { /* Still conflicts left on this symbol */ conflict_set[symbol] = 1; } } if (sizeof(indices(conflict_set))) { report(ERROR, "repair", "Still conflicts remaining in state\n%s\n" "on symbols (< %s >)", state_to_string(state), map(indices(conflict_set), symbol_to_string) * ", "); return ERROR_CONFLICTS; } else { report(WARNING, "repair", "All conflicts removed!"); return 0; } } #ifdef LR_PROFILE #define LR_GAUGE(X, BLOCK) \ report(NOTICE, "compile", X ": %f\n", gauge BLOCK) #else /* !LR_PROFILE */ #define LR_GAUGE(X, BLOCK) do BLOCK while(0) #endif /* LR_PROFILE */ //! Compiles the grammar into a parser, so that parse() can be called. int compile() { int lr_error = 0; /* No error yet */ int state_no = 0; /* DEBUG INFO */ Kernel state; multiset(int|string) symbols, conflicts; s_q = StateQueue(); s_q->push(first_state()); /* First make LR(0) states */ LR_GAUGE("LR0", { while (state = s_q->next()) { report(NOTICE, "compile", "Compiling state %d:\n%s", state_no++, state_to_string(state) + "\n"); /* Probably better implemented as a stack */ foreach (indices(state->goto_set()), int|string symbol) { state->do_goto(symbol); } } }); /* Compute nullables */ /* Done during add_rule */ report(NOTICE, "compile", "Nullable nonterminals: (< %s >)\n", map(indices(nullable), symbol_to_string) * ", "); LR_GAUGE("Master items", { /* Mark Transition and Reduction master items */ for (int index = 0; index < s_q->tail; index++) { mapping(int|string : Item) master_item =([]); foreach (s_q->arr[index]->items, Item i) { if (i->offset < sizeof(i->r->symbols)) { /* This is not a reduction item, which represent themselves */ int|string symbol = i->r->symbols[i->offset]; if (!(i->master_item = master_item[symbol])) { master_item[symbol] = i; } } } } }); /* Probably OK so far */ LR_GAUGE("LA sets", { /* Calculate look-ahead sets (DR and relation) */ for (int index = 0; index < s_q->tail; index++) { foreach (s_q->arr[index]->items, Item i) { if ((!i->master_item) && (i->offset != sizeof(i->r->symbols)) && (intp(i->r->symbols[i->offset]))) { /* This is a non-terminal master item */ foreach (i->next_state->items, Item i2) { int|string symbol; if (!i2->master_item) { /* Master item */ if (i2->offset != sizeof(i2->r->symbols)) { if (intp(symbol = i2->r->symbols[i2->offset])) { if (nullable[symbol]) { /* Add the item to the look-ahead relation set */ i->relation[i2] = 1; } } else { /* Add the string to the direct look-ahead set (DR) */ i->direct_lookahead[symbol] = 1; } } } } } } } }); LR_GAUGE("Handle shift", { /* Handle SHIFT-conflicts */ handle_shift_conflicts(); }); LR_GAUGE("Check shift", { /* Check the shift sets */ /* (Is this needed?) * Yes - initializes error_lookahead */ for (int index = 0; index < s_q->tail; index++) { foreach (s_q->arr[index]->items, Item i) { if ((!i->master_item) && (i->offset != sizeof(i->r->symbols)) && (intp(i->r->symbols[i->offset]))) { i->error_lookahead = copy_value(i->direct_lookahead); } } } }); LR_GAUGE("Lookback sets", { /* Compute lookback-sets */ for (int index = 0; index < s_q->tail; index++) { array(Item) items = s_q->arr[index]->items; // Set up a lookup table to speedup lookups later. mapping(int:array(Item)) lookup = ([]); foreach (items, Item i) { if (!i->offset) { if (!lookup[i->r->nonterminal]) { lookup[i->r->nonterminal] = ({ i }); } else { lookup[i->r->nonterminal] += ({ i }); } } } foreach (items, Item transition) { int|string symbol; if ((!transition->master_item) && (transition->offset != sizeof(transition->r->symbols)) && (intp(symbol = transition->r->symbols[transition->offset]))) { /* Master item and * Not a reduction item and * next symbol is a NonTerminal */ if (!lookup[symbol]) { // Foo? Shouldn't these always exist since we've made // a closure earlier? report(WARNING, "compile", "No item for symbol <%s>\n" "in state:\n" "%s", symbol_to_string(symbol), state_to_string(s_q->arr[index])); continue; } /* Find items which can reduce to the nonterminal from above */ foreach (lookup[symbol], Item i) { if (sizeof(i->r->symbols)) { if (go_through(i->next_state, i->item_id + 1, transition)) { /* Nullable */ Item master = i; if (i->master_item) { master = i->master_item; } /* Is this a nonterminal transition? */ if ((master->offset != sizeof(master->r->symbols)) && (intp(master->r->symbols[master->offset]))) { /* Don't include ourselves */ if (master != transition) { master->relation[transition] = 1; } } } } else { i->relation[transition] = 1; } } } } } }); LR_GAUGE("Handle follow", { /* Handle follow-conflicts */ handle_follow_conflicts(); }); LR_GAUGE("Compute LA", { /* Compute the lookahead (LA) */ for (int index = 0; index < s_q->tail; index++) { foreach (s_q->arr[index]->items, Item i) { if (i->offset == sizeof(i->r->symbols)) { /* Reduction item (always a master item) */ /* Calculate Look-ahead for all items in look-back set */ i->direct_lookahead=`|(i->direct_lookahead, @indices(i->relation)->direct_lookahead); } } } }); /* Probably OK from this point onward */ LR_GAUGE("Check conflicts", { /* Check for conflicts */ for (int index = 0; index < s_q->tail; index++) { Kernel state = s_q->arr[index]; conflicts = (<>); symbols = (<>); foreach (state->items, Item i) { if (i->offset == sizeof(i->r->symbols)) { /* Reduction */ conflicts |= i->direct_lookahead & symbols; symbols |= i->direct_lookahead; } else if (!i->master_item) { string|int symbol; /* Only master items, since we get * Shift-Shift conflicts otherwise */ if (!intp(symbol = i->r->symbols[i->offset])) { /* Shift on terminal */ if (symbols[symbol]) { conflicts[symbol] = 1; } else { symbols[symbol] = 1; } } } } if (sizeof(conflicts)) { /* Repair conflicts */ // int ov = verbose; // verbose = 1; lr_error = repair(state, conflicts); // verbose = ov; } else { report(NOTICE, "compile", "No conflicts in state:\n%s", state_to_string(s_q->arr[index])); } } }); LR_GAUGE("Compile actions", { /* Compile action tables */ for (int index = 0; index < s_q->tail; index++) { Kernel state = s_q->arr[index]; state->action = ([]); foreach (state->items, Item i) { if (i->next_state) { /* SHIFT */ state->action[i->r->symbols[i->offset]] = i->next_state; } else { foreach (indices(i->direct_lookahead), int|string symbol) { state->action[symbol] = i->r; } } } } start_state = s_q->arr[0]; }); #ifdef LR_PROFILE report(NOTICE, "compile", "DONE\n"); #endif /* LR_PROFILE */ return lr_error; } //! Parse the input according to the compiled grammar. //! The last value reduced is returned. //! //! @note //! The parser must have been compiled (with compile()) //! prior to calling this function. //! //! @bugs //! Errors should be throw()n. //! //! @param scanner //! The scanner function. It returns the next symbol from the input. //! It should either return a string (terminal) or an array with //! a string (terminal) and a mixed (value). //! EOF is indicated with the empty string. //! //! @param action_object //! Object used to resolve those actions that have been specified as //! strings. mixed parse(object|function(void:string|array(string|mixed)) scanner, void|object action_object) { ADT.Stack value_stack = ADT.Stack(4096); ADT.Stack state_stack = ADT.Stack(4096); Kernel state = start_state; string input; mixed value; lr_error = 0; /* No parse error yet */ if (!functionp(scanner) && !(objectp(scanner) && functionp(scanner->`()))) { report(ERROR, "parse", "parser->parse(): scanner not set!\n"); lr_error = ERROR_NO_SCANNER; return 0; } while (1) { mixed a; /* Read some input */ value = scanner(); if (arrayp(value)) { input = ([array(string)]value)[0]; value = ([array(mixed)]value)[1]; } else { input = [string]value; } while(1) { while (object_program(a = state->action[input]) == Rule) { Rule r = [object(Rule)]a; report(NOTICE, "parse", "Reducing according to rule\n%s\n", rule_to_string(r)); do { if (r->action) { /* REDUCE */ string|function func = 0; if (stringp(func = r->action)) { if (action_object) { func = [string|function]action_object[r->action]; if (!functionp(func)) { if (!func) { report(ERROR, "parse", "Missing action \"%s\" in object", r->action); lr_error |= ERROR_MISSING_ACTION; } else { report(ERROR, "parse", "Bad type (%s) for action \"%s\" in object", typeof(func), r->action); lr_error |= ERROR_BAD_ACTION_TYPE; func = 0; } } } else { report(ERROR, "parse", "Missing object for action \"%s\"", r->action); lr_error |= ERROR_NO_OBJECT; func = 0; } } if (func) { if (sizeof(r->symbols)) { value_stack->push(([function(mixed ...:mixed)]func) (@[array(mixed)]value_stack-> pop(sizeof(r->symbols)))); state = ([array(Kernel)]state_stack->pop(sizeof(r->symbols)))[0]; } else { value_stack->push(r->action()); } break; // Break out of the do-while. } } // Default action. if (sizeof(r->symbols)) { if (sizeof(r->symbols) > 1) { value_stack->quick_pop(sizeof(r->symbols) - 1); } state = ([array(Kernel)]state_stack->pop(sizeof(r->symbols)))[0]; } else { value_stack->push(0); } } while(0); state_stack->push(state); state = [object(Kernel)]state->action[r->nonterminal]; /* Goto */ } if (a) { /* SHIFT or ACCEPT */ if (input == "") { /* Only the final state is allowed to shift on ""(EOF) */ /* ACCEPT */ return value_stack->pop(); } /* SHIFT */ report(NOTICE, "parse", "Shifting \"%s\", value \"%O\"", input, value); value_stack->push(value); state_stack->push(state); state = [object(Kernel)]a; } else { /* ERROR */ if (input = "") { /* At end of file */ lr_error |= ERROR_EOF; if (sizeof(value_stack) != 1) { if (sizeof(value_stack)) { report(ERROR, "parse", "Bad state at EOF -- Throwing \"%O\"", value_stack->pop()); state = [object(Kernel)]state_stack->pop(); continue; } else { report(ERROR, "parse", "Empty stack at EOF!"); return 0; } } else { report(ERROR, "parse", "Bad state at EOF"); return value_stack->pop(); } } else { lr_error |= ERROR_SYNTAX; report(ERROR, "parse", "Bad input: %O(%O)", input, value); } } break; /* Break out of the inner while(1) to read more input. */ } } } }

pike.git/ lib/ modules/ Parser.pmod/ LR.pmod/ module.pmod > 9e1f00e1eac3ca183f070f8ce488d76abe6c6a9b [Annotate]