ack/lang/m2/comp/chk_expr.c

/* E X P R E S S I O N   C H E C K I N G */

/*	Check expressions, and try to evaluate them as far as possible.
*/

#include	"debug.h"

#include	<em_arith.h>
#include	<em_label.h>
#include	<assert.h>
#include	<alloc.h>

#include	"Lpars.h"
#include	"idf.h"
#include	"type.h"
#include	"def.h"
#include	"LLlex.h"
#include	"node.h"
#include	"scope.h"
#include	"const.h"
#include	"standards.h"
#include	"chk_expr.h"

extern char *symbol2str();

int
ChkVariable(expp)
	register struct node *expp;
{
	/*	Check that "expp" indicates an item that can be
		assigned to.
	*/

	if (! ChkDesignator(expp)) return 0;

	if (expp->nd_class == Def &&
	    !(expp->nd_def->df_kind & (D_FIELD|D_VARIABLE))) {
		node_error(expp, "variable expected");
		return 0;
	}

	return 1;
}

STATIC int
ChkArrow(expp)
	register struct node *expp;
{
	/*	Check an application of the '^' operator.
		The operand must be a variable of a pointer type.
	*/
	register struct type *tp;

	assert(expp->nd_class == Arrow);
	assert(expp->nd_symb == '^');

	expp->nd_type = error_type;

	if (! ChkVariable(expp->nd_right)) return 0;

	tp = expp->nd_right->nd_type;

	if (tp->tp_fund != T_POINTER) {
		node_error(expp, "illegal operand for unary operator \"^\"");
		return 0;
	}

	expp->nd_type = RemoveEqual(PointedtoType(tp));
	return 1;
}

STATIC int
ChkArr(expp)
	register struct node *expp;
{
	/*	Check an array selection.
		The left hand side must be a variable of an array type,
		and the right hand side must be an expression that is
		assignment compatible with the array-index.
	*/

	register struct type *tpl, *tpr;

	assert(expp->nd_class == Arrsel);
	assert(expp->nd_symb == '[');

	expp->nd_type = error_type;

	if ( 
	     !ChkVariable(expp->nd_left)
	   ||
	     !ChkExpression(expp->nd_right)
	   ||
	     expp->nd_left->nd_type == error_type
	   )	return 0;

	tpl = expp->nd_left->nd_type;
	tpr = expp->nd_right->nd_type;

	if (tpl->tp_fund != T_ARRAY) {
		node_error(expp, "not indexing an ARRAY type");
		return 0;
	}

	/* Type of the index must be assignment compatible with
	   the index type of the array (Def 8.1).
	   However, the index type of a conformant array is not specified.
	   Either INTEGER or CARDINAL seems reasonable.
	*/
	if (IsConformantArray(tpl) ? !TstAssCompat(card_type, tpr)
				   : !TstAssCompat(IndexType(tpl), tpr)) {
		node_error(expp, "incompatible index type");
		return 0;
	}

	expp->nd_type = RemoveEqual(tpl->arr_elem);
	return 1;
}

#ifdef DEBUG
STATIC int
ChkValue(expp)
	struct node *expp;
{
	switch(expp->nd_symb) {
	case REAL:
	case STRING:
	case INTEGER:
		return 1;

	default:
		crash("(ChkValue)");
	}
	/*NOTREACHED*/
}
#endif

STATIC int
ChkLinkOrName(expp)
	register struct node *expp;
{
	/*	Check either an ID or a construction of the form
		ID.ID [ .ID ]*
	*/
	register struct def *df;

	expp->nd_type = error_type;

	if (expp->nd_class == Name) {
		expp->nd_def = lookfor(expp, CurrVis, 1);
		expp->nd_class = Def;
		expp->nd_type = RemoveEqual(expp->nd_def->df_type);
	}
	else if (expp->nd_class == Link) {
		/*	A selection from a record or a module.
			Modules also have a record type.
		*/
		register struct node *left = expp->nd_left;

		assert(expp->nd_symb == '.');

		if (! ChkDesignator(left)) return 0;

		if (left->nd_type->tp_fund != T_RECORD ||
		    (left->nd_class == Def &&
		     !(left->nd_def->df_kind & (D_MODULE|D_VARIABLE|D_FIELD))
		    )
		   ) {
			node_error(left, "illegal selection");
			return 0;
		}

		if (!(df = lookup(expp->nd_IDF, left->nd_type->rec_scope))) {
			id_not_declared(expp);
			return 0;
		}
		else {
			expp->nd_def = df;
			expp->nd_type = RemoveEqual(df->df_type);
			expp->nd_class = LinkDef;
			if (!(df->df_flags & (D_EXPORTED|D_QEXPORTED))) {
				/* Fields of a record are always D_QEXPORTED,
				   so ...
				*/
node_error(expp, "identifier \"%s\" not exported from qualifying module",
df->df_idf->id_text);
				return 0;
			}
		}

		if (left->nd_class == Def &&
		    left->nd_def->df_kind == D_MODULE) {
			expp->nd_class = Def;
			FreeNode(left);
			expp->nd_left = 0;
		}
		else	return 1;
	}

	assert(expp->nd_class == Def);

	df = expp->nd_def;
	if (df->df_kind == D_ERROR) return 0;

	if (df->df_kind & (D_ENUM | D_CONST)) {
		/* Replace an enum-literal or a CONST identifier by its value.
		*/
		if (df->df_kind == D_ENUM) {
			expp->nd_class = Value;
			expp->nd_INT = df->enm_val;
			expp->nd_symb = INTEGER;
		}
		else  {
			unsigned int ln = expp->nd_lineno;

			assert(df->df_kind == D_CONST);
			*expp = *(df->con_const);
			expp->nd_lineno = ln;
		}
	}

	return 1;
}

STATIC int
ChkExLinkOrName(expp)
	register struct node *expp;
{
	/*	Check either an ID or an ID.ID [.ID]* occurring in an
		expression.
	*/
	register struct def *df;

	if (! ChkLinkOrName(expp)) return 0;
	if (expp->nd_class != Def) return 1;
	df = expp->nd_def;

	if (!(df->df_kind & D_VALUE)) {
		node_error(expp, "value expected");
	}

	if (df->df_kind == D_PROCEDURE) {
		/* Check that this procedure is one that we may take the
		   address from.
		*/
		if (df->df_type == std_type || df->df_scope->sc_level > 0) {
			/* Address of standard or nested procedure
			   taken.
			*/
node_error(expp, "standard or local procedures may not be assigned");
			return 0;
		}
	}

	return 1;
}

STATIC int
ChkElement(expp, tp, set)
	register struct node *expp;
	register struct type *tp;
	arith **set;
{
	/*	Check elements of a set. This routine may call itself
		recursively.
		Also try to compute the set!
	*/
	register struct node *left = expp->nd_left;
	register struct node *right = expp->nd_right;
	register int i;

	if (expp->nd_class == Link && expp->nd_symb == UPTO) {
		/* { ... , expr1 .. expr2,  ... }
		   First check expr1 and expr2, and try to compute them.
		*/
		if (!ChkElement(left, tp, set) || !ChkElement(right, tp, set)) {
			return 0;
		}

		if (left->nd_class == Value && right->nd_class == Value) {
			/* We have a constant range. Put all elements in the
			   set
			*/

		    	if (left->nd_INT > right->nd_INT) {
node_error(expp, "lower bound exceeds upper bound in range");
				return 0;
			}

			if (*set) {
				for (i=left->nd_INT+1; i<right->nd_INT; i++) {
					(*set)[i/wrd_bits] |= (1<<(i%wrd_bits));
				}
			}
		}
		else if (*set) {
			free((char *) *set);
			*set = 0;
		}

		return 1;
	}

	/* Here, a single element is checked
	*/
	if (!ChkExpression(expp)) return 0;

	if (!TstCompat(tp, expp->nd_type)) {
		node_error(expp, "set element has incompatible type");
		return 0;
	}

	if (expp->nd_class == Value) {
		/* a constant element
		*/
		arith low, high;

		i = expp->nd_INT;
		getbounds(tp, &low, &high);

	    	if (i < low || i > high) {
			node_error(expp, "set element out of range");
			return 0;
		}

		if (*set) (*set)[i/wrd_bits] |= (1 << (i%wrd_bits));
	}

	return 1;
}

STATIC int
ChkSet(expp)
	register struct node *expp;
{
	/*	Check the legality of a SET aggregate, and try to evaluate it
		compile time. Unfortunately this is all rather complicated.
	*/
	register struct type *tp;
	register struct node *nd;
	register struct def *df;
	arith *set;
	unsigned size;

	assert(expp->nd_symb == SET);

	/* First determine the type of the set
	*/
	if (nd = expp->nd_left) {
		/* A type was given. Check it out
		*/
		if (! ChkDesignator(nd)) return 0;

		assert(nd->nd_class == Def);
		df = nd->nd_def;

		if (!is_type(df) ||
		    (df->df_type->tp_fund != T_SET)) {
			if (df->df_kind != D_ERROR) {
node_error(expp, "type specifier does not represent a set type");
			}
			return 0;
		}
		tp = df->df_type;
		FreeNode(expp->nd_left);
		expp->nd_left = 0;
	}
	else	tp = bitset_type;
	expp->nd_type = tp;

	nd = expp->nd_right;

	/* Now check the elements given, and try to compute a constant set.
	   First allocate room for the set, but only if it is'nt empty.
	*/
	if (! nd) {
		/* The resulting set IS empty, so we just return
		*/
		expp->nd_class = Set;
		expp->nd_set = 0;
		return 1;
	}
	size = tp->tp_size * (sizeof(arith) / word_size);
	set = (arith *) Malloc(size);
	clear((char *) set, size);

	/* Now check the elements, one by one
	*/
	while (nd) {
		assert(nd->nd_class == Link && nd->nd_symb == ',');

		if (!ChkElement(nd->nd_left, ElementType(tp), &set)) return 0;
		nd = nd->nd_right;
	}

	if (set) {
		/* Yes, it was a constant set, and we managed to compute it!
		   Notice that at the moment there is no such thing as
		   partial evaluation. Either we evaluate the set, or we
		   don't (at all). Improvement not neccesary (???)
		   ??? sets have a contant part and a variable part ???
		*/
		expp->nd_class = Set;
		expp->nd_set = set;
		FreeNode(expp->nd_right);
		expp->nd_right = 0;
	}

	return 1;
}

STATIC struct node *
getarg(argp, bases, designator)
	struct node **argp;
{
	/*	This routine is used to fetch the next argument from an
		argument list. The argument list is indicated by "argp".
		The parameter "bases" is a bitset indicating which types
		are allowed at this point, and "designator" is a flag
		indicating that the address from this argument is taken, so
		that it must be a designator and may not be a register
		variable.
	*/
	register struct node *arg = (*argp)->nd_right;
	register struct node *left;

	if (! arg) {
		node_error(*argp, "too few arguments supplied");
		return 0;
	}

	left = arg->nd_left;

	if (designator ? !ChkVariable(left) : !ChkExpression(left)) {
		return 0;
	}

	if (designator && left->nd_class == Def) {
		left->nd_def->df_flags |= D_NOREG;
	}

	if (bases) {
		if (!(BaseType(left->nd_type)->tp_fund & bases)) {
			node_error(arg, "unexpected type");
			return 0;
		}
	}

	*argp = arg;
	return left;
}

STATIC struct node *
getname(argp, kinds)
	struct node **argp;
{
	/*	Get the next argument from argument list "argp".
		The argument must indicate a definition, and the
		definition kind must be one of "kinds".
	*/
	register struct node *arg = *argp;
	register struct node *left;

	if (!arg->nd_right) {
		node_error(arg, "too few arguments supplied");
		return 0;
	}

	arg = arg->nd_right;
	left = arg->nd_left;
	if (! ChkDesignator(left)) return 0;

	if (left->nd_class != Def && left->nd_class != LinkDef) {
		node_error(arg, "identifier expected");
		return 0;
	}

	if (!(left->nd_def->df_kind & kinds)) {
		node_error(arg, "unexpected type");
		return 0;
	}

	*argp = arg;
	return left;
}

STATIC int
ChkProcCall(expp)
	struct node *expp;
{
	/*	Check a procedure call
	*/
	register struct node *left;
	struct node *arg;
	register struct paramlist *param;

	left = expp->nd_left;
	expp->nd_type = RemoveEqual(ResultType(left->nd_type));

	/* Check parameter list
	*/
	for (param = ParamList(left->nd_type); param; param = param->next) {
		if (!(left = getarg(&expp, 0, IsVarParam(param)))) return 0;
		if (left->nd_symb == STRING) {
			TryToString(left, TypeOfParam(param));
		}
		if (! TstParCompat(RemoveEqual(TypeOfParam(param)),
				   left->nd_type,
				   IsVarParam(param),
				   left)) {
node_error(left, "type incompatibility in parameter");
			return 0;
		}
	}

	if (expp->nd_right) {
		node_error(expp->nd_right, "too many parameters supplied");
		return 0;
	}

	return 1;
}

int
ChkCall(expp)
	register struct node *expp;
{
	/*	Check something that looks like a procedure or function call.
		Of course this does not have to be a call at all,
		it may also be a cast or a standard procedure call.
	*/
	register struct node *left;
	STATIC int ChkStandard();
	STATIC int ChkCast();

	/* First, get the name of the function or procedure
	*/
	expp->nd_type = error_type;
	left = expp->nd_left;
	if (! ChkDesignator(left)) return 0;

	if (IsCast(left)) {
		/* It was a type cast.
		*/
		return ChkCast(expp, left);
	}

	if (IsProcCall(left)) {
		/* A procedure call.
		   It may also be a call to a standard procedure
		*/
		if (left->nd_type == std_type) {
			/* A standard procedure
			*/
			return ChkStandard(expp, left);
		}
		/* Here, we have found a real procedure call. The left hand
		   side may also represent a procedure variable.
		*/
		return ChkProcCall(expp);
	}

	node_error(left, "procedure, type, or function expected");
	return 0;
}

STATIC struct type *
ResultOfOperation(operator, tp)
	struct type *tp;
{
	/*	Return the result type of the binary operation "operator",
		with operand type "tp".
	*/

	switch(operator) {
	case '=':
	case '#':
	case GREATEREQUAL:
	case LESSEQUAL:
	case '<':
	case '>':
	case IN:
		return bool_type;
	}

	return tp;
}

STATIC int
Boolean(operator)
{
	return operator == OR || operator == AND || operator == '&';
}

STATIC int
AllowedTypes(operator)
{
	/*	Return a bit mask indicating the allowed operand types
		for binary operator "operator".
	*/

	switch(operator) {
	case '+':
	case '-':
	case '*':
		return T_NUMERIC|T_SET;
	case '/':
		return T_REAL|T_SET;
	case DIV:
	case MOD:
		return T_INTORCARD;
	case OR:
	case AND:
	case '&':
		return T_ENUMERATION;
	case '=':
	case '#':
		return T_POINTER|T_HIDDEN|T_SET|T_NUMERIC|T_ENUMERATION|T_CHAR;
	case GREATEREQUAL:
	case LESSEQUAL:
		return T_SET|T_NUMERIC|T_CHAR|T_ENUMERATION;
	case '<':
	case '>':
		return T_NUMERIC|T_CHAR|T_ENUMERATION;
	default:
		crash("(AllowedTypes)");
	}
	/*NOTREACHED*/
}

STATIC int
ChkAddress(tpl, tpr)
	register struct type *tpl, *tpr;
{
	/*	Check that either "tpl" or "tpr" are both of type
		address_type, or that one of them is, but the other is
		of type cardinal.
	*/
	
	if (tpl == address_type) {
		return tpr == address_type || (tpr->tp_fund & T_CARDINAL);
	}

	if (tpr == address_type) {
		return (tpl->tp_fund & T_CARDINAL);
	}

	return 0;
}

STATIC int
ChkBinOper(expp)
	register struct node *expp;
{
	/*	Check a binary operation.
	*/
	register struct node *left, *right;
	struct type *tpl, *tpr;
	int allowed;

	left = expp->nd_left;
	right = expp->nd_right;

	if (!ChkExpression(left) || !ChkExpression(right)) return 0;

	tpl = BaseType(left->nd_type);
	tpr = BaseType(right->nd_type);

	if (tpl == intorcard_type) {
		if (tpr == int_type || tpr == card_type) {
			 left->nd_type = tpl = tpr;
		}
	}
	if (tpr == intorcard_type) {
		if (tpl == int_type || tpl == card_type) {
			right->nd_type = tpr = tpl;
		}
	}

	expp->nd_type = ResultOfOperation(expp->nd_symb, tpr);

	/* Check that the application of the operator is allowed on the type
	   of the operands.
	   There are three tricky parts:
	   - Boolean operators are only allowed on boolean operands, but
	     the "allowed-mask" of "AllowedTypes" can only indicate
	     an enumeration type.
	   - All operations that are allowed on CARDINALS are also allowed
	     on ADDRESS.
	   - The IN-operator has as right-hand-size operand a set.
	*/
	if (expp->nd_symb == IN) {
		if (!TstAssCompat(tpl, ElementType(tpr))) {
			/* Assignment compatible ???
			   I don't know! Should we be allowed to check
			   if a CARDINAL is a member of a BITSET???
			*/

node_error(expp, "incompatible types for operator \"IN\"");
			return 0;
		}
		if (left->nd_class == Value && right->nd_class == Set) {
			cstset(expp);
		}
		return 1;
	}

	allowed = AllowedTypes(expp->nd_symb);

	if (!(tpr->tp_fund & allowed) || !(tpl->tp_fund & allowed)) {
	    	if (!((T_CARDINAL & allowed) &&
	             ChkAddress(tpl, tpr))) {
node_error(expp,"operator \"%s\": illegal operand type(s)", symbol2str(expp->nd_symb));
			return 0;
		}
		if (expp->nd_type->tp_fund & T_CARDINAL) {
			expp->nd_type = address_type;
		}
	}

	if (Boolean(expp->nd_symb) && tpl != bool_type) {
node_error(expp,"operator \"%s\": illegal operand type(s)", symbol2str(expp->nd_symb));
	    
		return 0;
	}

	/* Operands must be compatible (distilled from Def 8.2)
	*/
	if (!TstCompat(tpl, tpr)) {
		node_error(expp, "incompatible types for operator \"%s\"",
					symbol2str(expp->nd_symb));
		return 0;
	}

	if (tpl->tp_fund == T_SET) {
	    	if (left->nd_class == Set && right->nd_class == Set) {
			cstset(expp);
		}
	}
	else if ( tpl->tp_fund != T_REAL &&
		  left->nd_class == Value && right->nd_class == Value) {
		cstbin(expp);
	}

	return 1;
}

STATIC int
ChkUnOper(expp)
	register struct node *expp;
{
	/*	Check an unary operation.
	*/
	register struct node *right = expp->nd_right;
	register struct type *tpr;

	if (! ChkExpression(right)) return 0;

	expp->nd_type = tpr = BaseType(right->nd_type);
	if (tpr == address_type) tpr = card_type;

	switch(expp->nd_symb) {
	case '+':
		if (tpr->tp_fund & T_NUMERIC) {
			expp->nd_token = right->nd_token;
			expp->nd_class = right->nd_class;
			FreeNode(right);
			expp->nd_right = 0;
			return 1;
		}
		break;

	case '-':
		if (tpr->tp_fund & T_INTORCARD) {
			if (tpr == intorcard_type) {
				expp->nd_type = int_type;
			}
			if (right->nd_class == Value) {
				cstunary(expp);
			}
			return 1;
		}
		else if (tpr->tp_fund == T_REAL) {
			expp->nd_type = tpr;
			if (right->nd_class == Value) {
				if (*(right->nd_REL) == '-') (right->nd_REL)++;
				else (right->nd_REL)--;
				expp->nd_class = Value;
				expp->nd_symb = REAL;
				expp->nd_REL = right->nd_REL;
				FreeNode(right);
				expp->nd_right = 0;
			}
			return 1;
		}
		break;

	case NOT:
	case '~':
		if (tpr == bool_type) {
			if (right->nd_class == Value) {
				cstunary(expp);
			}
			return 1;
		}
		break;

	default:
		crash("ChkUnOper");
	}
	node_error(expp, "illegal operand for unary operator \"%s\"",
			symbol2str(expp->nd_symb));
	return 0;
}

STATIC struct node *
getvariable(argp)
	struct node **argp;
{
	/*	Get the next argument from argument list "argp".
		It must obey the rules of "ChkVariable".
	*/
	register struct node *arg = *argp;

	arg = arg->nd_right;
	if (!arg) {
		node_error(arg, "too few parameters supplied");
		return 0;
	}

	*argp = arg;
	arg = arg->nd_left;
	if (! ChkVariable(arg)) return 0;

	return arg;
}

STATIC int
ChkStandard(expp, left)
	register struct node *expp, *left;
{
	/*	Check a call of a standard procedure or function
	*/
	struct node *arg = expp;
	int std;

	assert(left->nd_class == Def);
	std = left->nd_def->df_value.df_stdname;

	switch(std) {
	case S_ABS:
		if (!(left = getarg(&arg, T_NUMERIC, 0))) return 0;
		expp->nd_type = left->nd_type;
		if (left->nd_class == Value &&
		    expp->nd_type->tp_fund != T_REAL) {
			cstcall(expp, S_ABS);
		}
		break;

	case S_CAP:
		expp->nd_type = char_type;
		if (!(left = getarg(&arg, T_CHAR, 0))) return 0;
		if (left->nd_class == Value) cstcall(expp, S_CAP);
		break;

	case S_CHR:
		expp->nd_type = char_type;
		if (!(left = getarg(&arg, T_INTORCARD, 0))) return 0;
		if (left->nd_class == Value) cstcall(expp, S_CHR);
		break;

	case S_FLOAT:
		expp->nd_type = real_type;
		if (!(left = getarg(&arg, T_INTORCARD, 0))) return 0;
		break;

	case S_HIGH:
		if (!(left = getarg(&arg, T_ARRAY, 0))) return 0;
		if (IsConformantArray(left->nd_type)) {
			/* A conformant array has no explicit index type
			   ??? So, what can we use as index-type ???
			*/
			expp->nd_type = intorcard_type;
		}
		else {
			expp->nd_type = IndexType(left->nd_type);
			cstcall(expp, S_MAX);
		}
		break;

	case S_MAX:
	case S_MIN:
		if (!(left = getname(&arg, D_ISTYPE))) return 0;
		if (!(left->nd_type->tp_fund & (T_DISCRETE))) {
node_error(left, "illegal type in %s", std == S_MAX ? "MAX" : "MIN");
			return 0;
		}
		expp->nd_type = left->nd_type;
		cstcall(expp,std);
		break;

	case S_ODD:
		if (!(left = getarg(&arg, T_INTORCARD, 0))) return 0;
		expp->nd_type = bool_type;
		if (left->nd_class == Value) cstcall(expp, S_ODD);
		break;

	case S_ORD:
		if (!(left = getarg(&arg, T_DISCRETE, 0))) return 0;
		if (left->nd_type->tp_size > word_size) {
			node_error(left, "illegal type in argument of ORD");
			return 0;
		}
		expp->nd_type = card_type;
		if (left->nd_class == Value) cstcall(expp, S_ORD);
		break;

	case S_NEW:
	case S_DISPOSE:
		{
			static int warning_given = 0;

			if (!warning_given) {
				warning_given = 1;
				node_warning(expp, "NEW and DISPOSE are old-fashioned");
			}
		}
		if (! (left = getvariable(&arg))) return 0;
		if (! (left->nd_type->tp_fund == T_POINTER)) {
			node_error(left, "pointer variable expected");
			return 0;
		}
		if (left->nd_class == Def) {
			left->nd_def->df_flags |= D_NOREG;
		}
		/* Now, make it look like a call to ALLOCATE or DEALLOCATE */
		{
			struct token dt;
			struct node *nd;

			dt.TOK_INT = PointedtoType(left->nd_type)->tp_size;
			dt.tk_symb = INTEGER;
			dt.tk_lineno = left->nd_lineno;
			nd = MkLeaf(Value, &dt);
			nd->nd_type = card_type;
			dt.tk_symb = ',';
			arg->nd_right = MkNode(Link, nd, NULLNODE, &dt);
			/* Ignore other arguments to NEW and/or DISPOSE ??? */

			FreeNode(expp->nd_left);
			dt.tk_symb = IDENT;
			dt.tk_lineno = expp->nd_left->nd_lineno;
			dt.TOK_IDF = str2idf(std == S_NEW ?
						"ALLOCATE" : "DEALLOCATE", 0);
			expp->nd_left = MkLeaf(Name, &dt);
		}
		return ChkCall(expp);

	case S_TSIZE:	/* ??? */
	case S_SIZE:
		expp->nd_type = intorcard_type;
		if (! getname(&arg, D_FIELD|D_VARIABLE|D_ISTYPE)) return 0;
		cstcall(expp, S_SIZE);
		break;

	case S_TRUNC:
		expp->nd_type = card_type;
		if (!(left = getarg(&arg, T_REAL, 0))) return 0;
		break;

	case S_VAL:
		{
		struct type *tp;

		if (!(left = getname(&arg, D_ISTYPE))) return 0;
		tp = left->nd_def->df_type;
		if (!(tp->tp_fund & T_DISCRETE)) {
			node_error(arg, "unexpected type");
			return 0;
		}
		expp->nd_type = left->nd_def->df_type;
		expp->nd_right = arg->nd_right;
		arg->nd_right = 0;
		FreeNode(arg);
		arg = expp;
		if (!(left = getarg(&arg, T_INTORCARD, 0))) return 0;
		if (left->nd_class == Value) cstcall(expp, S_VAL);
		break;
		}

	case S_ADR:
		expp->nd_type = address_type;
		if (!(left = getarg(&arg, 0, 1))) return 0;
		break;

	case S_DEC:
	case S_INC:
		expp->nd_type = 0;
		if (! (left = getvariable(&arg))) return 0;
		if (! (left->nd_type->tp_fund & T_DISCRETE)) {
node_error(left,"illegal type in argument of %s",std == S_INC ? "INC" : "DEC");
			return 0;
		}
		if (arg->nd_right) {
			if (! getarg(&arg, T_INTORCARD, 0)) return 0;
		}
		break;

	case S_HALT:
		expp->nd_type = 0;
		break;

	case S_EXCL:
	case S_INCL:
		{
		struct type *tp;

		expp->nd_type = 0;
		if (!(left = getvariable(&arg))) return 0;
		tp = left->nd_type;
		if (tp->tp_fund != T_SET) {
node_error(arg, "%s expects a SET parameter", std == S_EXCL ? "EXCL" : "INCL");
			return 0;
		}
		if (!(left = getarg(&arg, T_DISCRETE, 0))) return 0;
		if (!TstAssCompat(ElementType(tp), left->nd_type)) {
			/* What type of compatibility do we want here?
			   apparently assignment compatibility! ??? ???
			*/
			node_error(arg, "unexpected type");
			return 0;
		}
		break;
		}

	default:
		crash("(ChkStandard)");
	}

	if (arg->nd_right) {
		node_error(arg->nd_right, "too many parameters supplied");
		return 0;
	}

	return 1;
}

STATIC int
ChkCast(expp, left)
	register struct node *expp, *left;
{
	/*	Check a cast and perform it if the argument is constant.
		If the sizes don't match, only complain if at least one of them
		has a size larger than the word size.
		If both sizes are equal to or smaller than the word size, there
		is no problem as such values take a word on the EM stack
		anyway.
	*/
	register struct node *arg = expp->nd_right;

	if ((! arg) || arg->nd_right) {
node_error(expp, "only one parameter expected in type cast");
		return 0;
	}

	arg = arg->nd_left;
	if (! ChkExpression(arg)) return 0;

	if (arg->nd_type->tp_size != left->nd_type->tp_size &&
	    (arg->nd_type->tp_size > word_size ||
	     left->nd_type->tp_size > word_size)) {
		node_error(expp, "unequal sizes in type cast");
	}

	if (arg->nd_class == Value) {
		struct type *tp = left->nd_type;

		FreeNode(left);
		expp->nd_right->nd_left = 0;
		FreeNode(expp->nd_right);
		expp->nd_left = expp->nd_right = 0;
		*expp = *arg;
		expp->nd_type = tp;
	}
	else expp->nd_type = left->nd_type;

	return 1;
}

TryToString(nd, tp)
	struct node *nd;
	struct type *tp;
{
	/*	Try a coercion from character constant to string.
	*/

	assert(nd->nd_symb == STRING);

	if (tp->tp_fund == T_ARRAY && nd->nd_type == char_type) {
		int ch = nd->nd_INT;

		nd->nd_type = standard_type(T_STRING, 1, (arith) 2);
		nd->nd_token.tk_data.tk_str = 
			(struct string *) Malloc(sizeof(struct string));
		nd->nd_STR = Salloc("X", 2);
		*(nd->nd_STR) = ch;
		nd->nd_SLE = 1;
	}
}

STATIC int
no_desig(expp)
	struct node *expp;
{
	node_error(expp, "designator expected");
	return 0;
}

STATIC int
done_before(expp)
	struct node *expp;
{
	return 1;
}

extern int	NodeCrash();

int (*ExprChkTable[])() = {
#ifdef DEBUG
	ChkValue,
#else
	done_before,
#endif
	ChkArr,
	ChkBinOper,
	ChkUnOper,
	ChkArrow,
	ChkCall,
	ChkExLinkOrName,
	NodeCrash,
	ChkSet,
	NodeCrash,
	NodeCrash,
	ChkExLinkOrName,
	NodeCrash
};

int (*DesigChkTable[])() = {
#ifdef DEBUG
	ChkValue,
#else
	done_before,
#endif
	ChkArr,
	no_desig,
	no_desig,
	ChkArrow,
	no_desig,
	ChkLinkOrName,
	NodeCrash,
	no_desig,
	done_before,
	NodeCrash,
	ChkLinkOrName,
	done_before
};