X-Git-Url: https://ocean-lang.org/code/?p=ocean;a=blobdiff_plain;f=csrc%2Foceani.mdc;h=e7976cf086ef03b338527549a4d3d069af7afd45;hp=7371535bf7c555ec127028eb89f3113901be0561;hb=ef3bbba20f9e426125498f78fe3b1f4ea75de68a;hpb=57c69adf13069b9daf3ed59f4401f16de3312975

diff --git a/csrc/oceani.mdc b/csrc/oceani.mdc
index 7371535..e7976cf 100644
--- a/csrc/oceani.mdc
+++ b/csrc/oceani.mdc
@@ -242,9 +242,11 @@ structures can be used.
 
 		parse_oceani(ss->code, &context.config, dotrace ? stderr : NULL);
 
+		resolve_consts(&context);
+		prepare_types(&context);
 		if (!context.parse_error && !analyse_funcs(&context)) {
 			fprintf(stderr, "oceani: type error in program - not running.\n");
-			context.parse_error = 1;
+			context.parse_error += 1;
 		}
 
 		if (doprint) {
@@ -265,6 +267,7 @@ structures can be used.
 		while (context.scope_depth > 0)
 			scope_pop(&context);
 		## free global vars
+		## free const decls
 		## free context types
 		## free context storage
 		exit(context.parse_error ? 1 : 0);
@@ -364,6 +367,7 @@ context so indicate that parsing failed.
 	static void type_err(struct parse_context *c,
 	                     char *fmt, struct exec *loc,
 	                     struct type *t1, int rules, struct type *t2);
+	static void tok_err(struct parse_context *c, char *fmt, struct token *t);
 
 ###### core functions
 
@@ -392,14 +396,14 @@ context so indicate that parsing failed.
 			}
 		}
 		fputs("\n", stderr);
-		c->parse_error = 1;
+		c->parse_error += 1;
 	}
 
 	static void tok_err(struct parse_context *c, char *fmt, struct token *t)
 	{
 		fprintf(stderr, "%s:%d:%d: %s: %.*s\n", c->file_name, t->line, t->col, fmt,
 			t->txt.len, t->txt.txt);
-		c->parse_error = 1;
+		c->parse_error += 1;
 	}
 
 ## Entities: declared and predeclared.
@@ -580,15 +584,20 @@ program and looking for errors.
 
 So `propagate_types` is passed an expected type (being a `struct type`
 pointer together with some `val_rules` flags) that the `exec` is
-expected to return, and returns the type that it does return, either
-of which can be `NULL` signifying "unknown".  An `ok` flag is passed
-by reference. It is set to `0` when an error is found, and `2` when
-any change is made.  If it remains unchanged at `1`, then no more
-propagation is needed.
+expected to return, and returns the type that it does return, either of
+which can be `NULL` signifying "unknown".  A `prop_err` flag set is
+passed by reference.  It has `Efail` set when an error is found, and
+`Eretry` when the type for some element is set via propagation.  If
+any expression cannot be evaluated immediately, `Enoconst` is set.
+If the expression can be copied, `Emaycopy` is set.
+
+If it remains unchanged at `0`, then no more propagation is needed.
 
 ###### ast
 
 	enum val_rules {Rnolabel = 1<<0, Rboolok = 1<<1, Rnoconstant = 1<<2};
+	enum prop_err {Efail = 1<<0, Eretry = 1<<1, Enoconst = 1<<2,
+		       Emaycopy = 1<<3};
 
 ###### format cases
 	case 'r':
@@ -597,11 +606,11 @@ propagation is needed.
 		break;
 
 ###### forward decls
-	static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
+	static struct type *propagate_types(struct exec *prog, struct parse_context *c, enum prop_err *perr,
 	                                    struct type *type, int rules);
 ###### core functions
 
-	static struct type *__propagate_types(struct exec *prog, struct parse_context *c, int *ok,
+	static struct type *__propagate_types(struct exec *prog, struct parse_context *c, enum prop_err *perr,
 	                                      struct type *type, int rules)
 	{
 		struct type *t;
@@ -623,13 +632,14 @@ propagation is needed.
 		return Tnone;
 	}
 
-	static struct type *propagate_types(struct exec *prog, struct parse_context *c, int *ok,
+	static struct type *propagate_types(struct exec *prog, struct parse_context *c, enum prop_err *perr,
 	                                    struct type *type, int rules)
 	{
-		struct type *ret = __propagate_types(prog, c, ok, type, rules);
+		int pre_err = c->parse_error;
+		struct type *ret = __propagate_types(prog, c, perr, type, rules);
 
-		if (c->parse_error)
-			*ok = 0;
+		if (c->parse_error > pre_err)
+			*perr |= Efail;
 		return ret;
 	}
 
@@ -647,6 +657,9 @@ the location of a value, which can be updated, in `lval`.  Others will
 set `lval` to NULL indicating that there is a value of appropriate type
 in `rval`.
 
+###### forward decls
+	static struct value interp_exec(struct parse_context *c, struct exec *e,
+					struct type **typeret);
 ###### core functions
 
 	struct lrval {
@@ -779,10 +792,11 @@ which might be reported in error messages.
 	struct type {
 		struct text name;
 		struct type *next;
+		struct token first_use;
 		int size, align;
 		int anon;
 		void (*init)(struct type *type, struct value *val);
-		void (*prepare_type)(struct parse_context *c, struct type *type, int parse_time);
+		int (*prepare_type)(struct parse_context *c, struct type *type, int parse_time);
 		void (*print)(struct type *type, struct value *val, FILE *f);
 		void (*print_type)(struct type *type, FILE *f);
 		int (*cmp_order)(struct type *t1, struct type *t2,
@@ -826,7 +840,10 @@ which might be reported in error messages.
 		struct type *n;
 
 		n = calloc(1, sizeof(*n));
-		*n = *proto;
+		if (proto)
+			*n = *proto;
+		else
+			n->size = -1;
 		n->name = s;
 		n->anon = anon;
 		n->next = c->typelist;
@@ -911,6 +928,40 @@ which might be reported in error messages.
 			fprintf(f, "*Unknown*");		// NOTEST
 	}
 
+	static void prepare_types(struct parse_context *c)
+	{
+		struct type *t;
+		int retry = 1;
+		enum { none, some, cannot } progress = none;
+
+		while (retry) {
+			retry = 0;
+
+			for (t = c->typelist; t; t = t->next) {
+				if (t->size < 0)
+					tok_err(c, "error: type used but not declared",
+						 &t->first_use);
+				if (t->size == 0 && t->prepare_type) {
+					if (t->prepare_type(c, t, 1))
+						progress = some;
+					else if (progress == cannot)
+						tok_err(c, "error: type has recursive definition",
+							&t->first_use);
+					else
+						retry = 1;
+				}
+			}
+			switch (progress) {
+			case cannot:
+				retry = 0; break;
+			case none:
+				progress = cannot; break;
+			case some:
+				progress = none; break;
+			}
+		}
+	}
+
 ###### forward decls
 
 	static void free_value(struct type *type, struct value *v);
@@ -947,12 +998,10 @@ symbol for those.
 
 	$*type
 	Type -> IDENTIFIER ${
-		$0 = find_type(c, $1.txt);
+		$0 = find_type(c, $ID.txt);
 		if (!$0) {
-			tok_err(c,
-				"error: undefined type", &$1);
-
-			$0 = Tnone;
+			$0 = add_type(c, $ID.txt, NULL);
+			$0->first_use = $ID;
 		}
 	}$
 	## type grammar
@@ -1110,7 +1159,7 @@ A separate function encoding these cases will simplify some code later.
 			mpf_t fl;
 			mpf_init2(fl, 20);
 			mpf_set_q(fl, v->num);
-			gmp_fprintf(f, "%Fg", fl);
+			gmp_fprintf(f, "%.10Fg", fl);
 			mpf_clear(fl);
 			break;
 			}
@@ -1224,6 +1273,7 @@ executable.
 		struct val *v = cast(val, e);
 		if (v->vtype == Tstr)
 			printf("\"");
+		// FIXME how to ensure numbers have same precision.
 		print_value(v->vtype, &v->val, stdout);
 		if (v->vtype == Tstr)
 			printf("\"");
@@ -1575,10 +1625,10 @@ need to be freed.  For this we need to be able to find it, so assume that
 		while (v) {
 			struct variable *next = v->previous;
 
-			if (v->global) {
+			if (v->global && v->frame_pos >= 0) {
 				free_value(v->type, var_value(&context, v));
-				if (v->depth == 0)
-					// This is a global constant
+				if (v->depth == 0 && v->type->free == function_free)
+					// This is a function constant
 					free_exec(v->where_decl);
 			}
 			free(v);
@@ -1845,13 +1895,17 @@ tell if it was set or not later.
 	short local_size;
 	void *global, *local;
 
+###### forward decls
+	static struct value *global_alloc(struct parse_context *c, struct type *t,
+					  struct variable *v, struct value *init);
+
 ###### ast functions
 
 	static struct value *var_value(struct parse_context *c, struct variable *v)
 	{
 		if (!v->global) {
 			if (!c->local || !v->type)
-				return NULL;			// NOTEST
+				return NULL;	// UNTESTED
 			if (v->frame_pos + v->type->size > c->local_size) {
 				printf("INVALID frame_pos\n");	// NOTEST
 				exit(2);			// NOTEST
@@ -1877,7 +1931,7 @@ tell if it was set or not later.
 			t->prepare_type(c, t, 1);	// NOTEST
 
 		if (c->global_size & (t->align - 1))
-			c->global_size = (c->global_size + t->align) & ~(t->align-1);
+			c->global_size = (c->global_size + t->align) & ~(t->align-1);	// NOTEST
 		if (!v) {
 			v = &scratch;
 			v->type = t;
@@ -2052,7 +2106,11 @@ correctly.
 		struct variable *v = var_ref(c, $1.txt);
 		$0 = new_pos(var, $1);
 		if (v == NULL) {
-			/* This might be a label - allocate a var just in case */
+			/* This might be a global const or a label
+			 * Allocate a var with impossible type Tnone,
+			 * which will be adjusted when we find out what it is,
+			 * or will trigger an error.
+			 */
 			v = var_decl(c, $1.txt);
 			if (v) {
 				v->type = Tnone;
@@ -2109,19 +2167,19 @@ correctly.
 			type_err(c, "error: variable used but not declared: %v",
 			         prog, NULL, 0, NULL);
 		if (v->type == NULL) {
-			if (type && *ok != 0) {
+			if (type && !(*perr & Efail)) {
 				v->type = type;
 				v->where_set = prog;
-				*ok = 2;
+				*perr |= Eretry;
 			}
-			return type;
-		}
-		if (!type_compat(type, v->type, rules)) {
+		} else if (!type_compat(type, v->type, rules)) {
 			type_err(c, "error: expected %1%r but variable '%v' is %2", prog,
 			         type, rules, v->type);
 			type_err(c, "info: this is where '%v' was set to %1", v->where_set,
 			         v->type, rules, NULL);
 		}
+		if (!v->global || v->frame_pos < 0)
+			*perr |= Enoconst;
 		if (!type)
 			return v->type;
 		return type;
@@ -2223,25 +2281,37 @@ with a const size by whether they are prepared at parse time or not.
 
 ###### value functions
 
-	static void array_prepare_type(struct parse_context *c, struct type *type,
+	static int array_prepare_type(struct parse_context *c, struct type *type,
 				       int parse_time)
 	{
 		struct value *vsize;
 		mpz_t q;
-		if (!type->array.vsize || type->array.static_size)
-			return;
-
-		vsize = var_value(c, type->array.vsize);
-		mpz_init(q);
-		mpz_tdiv_q(q, mpq_numref(vsize->num), mpq_denref(vsize->num));
-		type->array.size = mpz_get_si(q);
-		mpz_clear(q);
+		if (type->array.static_size)
+			return 1;	// UNTESTED
+		if (type->array.unspec && parse_time)
+			return 1;	// UNTESTED
+		if (parse_time && type->array.vsize && !type->array.vsize->global)
+			return 1;	// UNTESTED
 
-		if (parse_time) {
-			type->array.static_size = 1;
-			type->size = type->array.size * type->array.member->size;
-			type->align = type->array.member->align;
+		if (type->array.vsize) {
+			vsize = var_value(c, type->array.vsize);
+			if (!vsize)
+				return 1;	// UNTESTED
+			mpz_init(q);
+			mpz_tdiv_q(q, mpq_numref(vsize->num), mpq_denref(vsize->num));
+			type->array.size = mpz_get_si(q);
+			mpz_clear(q);
 		}
+		if (!parse_time)
+			return 1;
+		if (type->array.member->size <= 0)
+			return 0;
+
+		type->array.static_size = 1;
+		type->size = type->array.size * type->array.member->size;
+		type->align = type->array.member->align;
+
+		return 1;
 	}
 
 	static void array_init(struct type *type, struct value *val)
@@ -2356,9 +2426,6 @@ with a const size by whether they are prepared at parse time or not.
 		t->array.size = elements;
 		t->array.member = $<4;
 		t->array.vsize = NULL;
-		t->array.static_size = 1;
-		t->size = t->array.size * t->array.member->size;
-		t->align = t->array.member->align;
 	} }$
 
 	| [ IDENTIFIER ] Type ${ {
@@ -2422,8 +2489,8 @@ with a const size by whether they are prepared at parse time or not.
 		/* left must be an array, right must be a number,
 		 * result is the member type of the array
 		 */
-		propagate_types(b->right, c, ok, Tnum, 0);
-		t = propagate_types(b->left, c, ok, NULL, rules & Rnoconstant);
+		propagate_types(b->right, c, perr, Tnum, 0);
+		t = propagate_types(b->left, c, perr, NULL, rules & Rnoconstant);
 		if (!t || t->compat != array_compat) {
 			type_err(c, "error: %1 cannot be indexed", prog, t, 0, NULL);
 			return NULL;
@@ -2512,7 +2579,12 @@ function will be needed.
 			struct type *type;
 			struct value *init;
 			int offset;
-		} *fields;
+		} *fields; // This is created when field_list is analysed.
+		struct fieldlist {
+			struct fieldlist *prev;
+			struct field f;
+			struct exec *init;
+		} *field_list; // This is created during parsing
 	} structure;
 
 ###### type functions
@@ -2547,6 +2619,15 @@ function will be needed.
 		}
 	}
 
+	static void free_fieldlist(struct fieldlist *f)
+	{
+		if (!f)
+			return;
+		free_fieldlist(f->prev);
+		free_exec(f->init);
+		free(f);
+	}
+
 	static void structure_free_type(struct type *t)
 	{
 		int i;
@@ -2556,6 +2637,60 @@ function will be needed.
 				           t->structure.fields[i].init);
 			}
 		free(t->structure.fields);
+		free_fieldlist(t->structure.field_list);
+	}
+
+	static int structure_prepare_type(struct parse_context *c,
+					  struct type *t, int parse_time)
+	{
+		int cnt = 0;
+		struct fieldlist *f;
+
+		if (!parse_time || t->structure.fields)
+			return 1;
+
+		for (f = t->structure.field_list; f; f=f->prev) {
+			enum prop_err perr;
+			cnt += 1;
+
+			if (f->f.type->size <= 0)
+				return 0;
+			if (f->f.type->prepare_type)
+				f->f.type->prepare_type(c, f->f.type, parse_time);
+
+			if (f->init == NULL)
+				continue;
+			do {
+				perr = 0;
+				propagate_types(f->init, c, &perr, f->f.type, 0);
+			} while (perr & Eretry);
+			if (perr & Efail)
+				c->parse_error += 1;	// NOTEST
+		}
+
+		t->structure.nfields = cnt;
+		t->structure.fields = calloc(cnt, sizeof(struct field));
+		f = t->structure.field_list;
+		while (cnt > 0) {
+			int a = f->f.type->align;
+			cnt -= 1;
+			t->structure.fields[cnt] = f->f;
+			if (t->size & (a-1))
+				t->size = (t->size | (a-1)) + 1;
+			t->structure.fields[cnt].offset = t->size;
+			t->size += ((f->f.type->size - 1) | (a-1)) + 1;
+			if (a > t->align)
+				t->align = a;
+
+			if (f->init && !c->parse_error) {
+				struct value vl = interp_exec(c, f->init, NULL);
+				t->structure.fields[cnt].init =
+					global_alloc(c, f->f.type, NULL, &vl);
+			}
+
+			f = f->prev;
+		}
+		return 1;
 	}
 
 	static struct type structure_prototype = {
@@ -2563,6 +2698,7 @@ function will be needed.
 		.free = structure_free,
 		.free_type = structure_free_type,
 		.print_type_decl = structure_print_type,
+		.prepare_type = structure_prepare_type,
 	};
 
 ###### exec type
@@ -2620,7 +2756,7 @@ function will be needed.
 	case Xfieldref:
 	{
 		struct fieldref *f = cast(fieldref, prog);
-		struct type *st = propagate_types(f->left, c, ok, NULL, 0);
+		struct type *st = propagate_types(f->left, c, perr, NULL, 0);
 
 		if (!st)
 			type_err(c, "error: unknown type for field access", f->left,	// UNTESTED
@@ -2655,51 +2791,25 @@ function will be needed.
 		break;
 	}
 
-###### ast
-	struct fieldlist {
-		struct fieldlist *prev;
-		struct field f;
-	};
-
-###### ast functions
-	static void free_fieldlist(struct fieldlist *f)
-	{
-		if (!f)
-			return;
-		free_fieldlist(f->prev);
-		if (f->f.init) {
-			free_value(f->f.type, f->f.init);	// UNTESTED
-			free(f->f.init);	// UNTESTED
-		}
-		free(f);
-	}
-
 ###### top level grammar
 	DeclareStruct -> struct IDENTIFIER FieldBlock Newlines ${ {
-		struct type *t =
-			add_type(c, $2.txt, &structure_prototype);
-		int cnt = 0;
-		struct fieldlist *f;
-
-		for (f = $3; f; f=f->prev)
-			cnt += 1;
-
-		t->structure.nfields = cnt;
-		t->structure.fields = calloc(cnt, sizeof(struct field));
-		f = $3;
-		while (cnt > 0) {
-			int a = f->f.type->align;
-			cnt -= 1;
-			t->structure.fields[cnt] = f->f;
-			if (t->size & (a-1))
-				t->size = (t->size | (a-1)) + 1;
-			t->structure.fields[cnt].offset = t->size;
-			t->size += ((f->f.type->size - 1) | (a-1)) + 1;
-			if (a > t->align)
-				t->align = a;
-			f->f.init = NULL;
-			f = f->prev;
+		struct type *t;
+		t = find_type(c, $ID.txt);
+		if (!t)
+			t = add_type(c, $ID.txt, &structure_prototype);
+		else if (t->size >= 0) {
+			tok_err(c, "error: type already declared", &$ID);
+			tok_err(c, "info: this is location of declartion", &t->first_use);
+			/* Create a new one - duplicate */
+			t = add_type(c, $ID.txt, &structure_prototype);
+		} else {
+			struct type tmp = *t;
+			*t = structure_prototype;
+			t->name = tmp.name;
+			t->next = tmp.next;
 		}
+		t->structure.field_list = $<FB;
+		t->first_use = $ID;
 	} }$
 
 	$*fieldlist
@@ -2725,29 +2835,16 @@ function will be needed.
 	| ERROR ${ tok_err(c, "Syntax error in struct field", &$1); }$
 
 	Field -> IDENTIFIER : Type = Expression ${ {
-		int ok;
-
 		$0 = calloc(1, sizeof(struct fieldlist));
-		$0->f.name = $1.txt;
-		$0->f.type = $<3;
+		$0->f.name = $ID.txt;
+		$0->f.type = $<Type;
 		$0->f.init = NULL;
-		do {
-			ok = 1;
-			propagate_types($<5, c, &ok, $3, 0);
-		} while (ok == 2);
-		if (!ok)
-			c->parse_error = 1;	// UNTESTED
-		else {
-			struct value vl = interp_exec(c, $5, NULL);
-			$0->f.init = global_alloc(c, $0->f.type, NULL, &vl);
-		}
+		$0->init = $<Expr;
 	} }$
 	| IDENTIFIER : Type ${
 		$0 = calloc(1, sizeof(struct fieldlist));
-		$0->f.name = $1.txt;
-		$0->f.type = $<3;
-		if ($0->f.type->prepare_type)
-			$0->f.type->prepare_type(c, $0->f.type, 1);
+		$0->f.name = $ID.txt;
+		$0->f.type = $<Type;
 	}$
 
 ###### forward decls
@@ -2879,7 +2976,7 @@ further detailed when Expression Lists are introduced.
 	struct exec *function;
 
 ###### type functions
-	void (*check_args)(struct parse_context *c, int *ok,
+	void (*check_args)(struct parse_context *c, enum prop_err *perr,
 	                   struct type *require, struct exec *args);
 
 ###### value functions
@@ -2896,7 +2993,7 @@ further detailed when Expression Lists are introduced.
 		return 0;
 	}
 
-	static void function_check_args(struct parse_context *c, int *ok,
+	static void function_check_args(struct parse_context *c, enum prop_err *perr,
 	                                struct type *require, struct exec *args)
 	{
 		/* This should be 'compat', but we don't have a 'tuple' type to
@@ -2912,8 +3009,8 @@ further detailed when Expression Lists are introduced.
 					 args, NULL, 0, NULL);
 				break;
 			}
-			*ok = 1;
-			propagate_types(arg->left, c, ok, pv->var->type, 0);
+			*perr = 0;
+			propagate_types(arg->left, c, perr, pv->var->type, 0);
 			param = cast(binode, param->right);
 			arg = cast(binode, arg->right);
 		}
@@ -3112,7 +3209,10 @@ it in the "SimpleStatement Grammar" which will be described later.
 				 prog, NULL, 0, NULL);
 			return NULL;
 		}
-		v->var->type->check_args(c, ok, v->var->type, args);
+		*perr |= Enoconst;
+		v->var->type->check_args(c, perr, v->var->type, args);
+		if (v->var->type->function.inline_result)
+			*perr |= Emaycopy;
 		return v->var->type->function.return_type;
 	}
 
@@ -3225,9 +3325,9 @@ there.
 		struct binode *b2 = cast(binode, b->right);
 		struct type *t2;
 
-		propagate_types(b->left, c, ok, Tbool, 0);
-		t = propagate_types(b2->left, c, ok, type, Rnolabel);
-		t2 = propagate_types(b2->right, c, ok, type ?: t, Rnolabel);
+		propagate_types(b->left, c, perr, Tbool, 0);
+		t = propagate_types(b2->left, c, perr, type, Rnolabel);
+		t2 = propagate_types(b2->right, c, perr, type ?: t, Rnolabel);
 		return t ?: t2;
 	}
 
@@ -3394,8 +3494,8 @@ evaluate the second expression if not necessary.
 	case OrElse:
 	case Not:
 		/* both must be Tbool, result is Tbool */
-		propagate_types(b->left, c, ok, Tbool, 0);
-		propagate_types(b->right, c, ok, Tbool, 0);
+		propagate_types(b->left, c, perr, Tbool, 0);
+		propagate_types(b->right, c, perr, Tbool, 0);
 		if (type && type != Tbool)
 			type_err(c, "error: %1 operation found where %2 expected", prog,
 				   Tbool, 0, type);
@@ -3509,13 +3609,13 @@ expression operator, and the `CMPop` non-terminal will match one of them.
 	case Eql:
 	case NEql:
 		/* Both must match but not be labels, result is Tbool */
-		t = propagate_types(b->left, c, ok, NULL, Rnolabel);
+		t = propagate_types(b->left, c, perr, NULL, Rnolabel);
 		if (t)
-			propagate_types(b->right, c, ok, t, 0);
+			propagate_types(b->right, c, perr, t, 0);
 		else {
-			t = propagate_types(b->right, c, ok, NULL, Rnolabel);	// UNTESTED
+			t = propagate_types(b->right, c, perr, NULL, Rnolabel);	// UNTESTED
 			if (t)	// UNTESTED
-				t = propagate_types(b->left, c, ok, t, 0);	// UNTESTED
+				t = propagate_types(b->left, c, perr, t, 0);	// UNTESTED
 		}
 		if (!type_compat(type, Tbool, 0))
 			type_err(c, "error: Comparison returns %1 but %2 expected", prog,
@@ -3679,8 +3779,8 @@ parentheses around an expression converts it into a Term,
 	case Negate:
 		/* as propagate_types ignores a NULL,
 		 * unary ops fit here too */
-		propagate_types(b->left, c, ok, Tnum, 0);
-		propagate_types(b->right, c, ok, Tnum, 0);
+		propagate_types(b->left, c, perr, Tnum, 0);
+		propagate_types(b->right, c, perr, Tnum, 0);
 		if (!type_compat(type, Tnum, 0))
 			type_err(c, "error: Arithmetic returns %1 but %2 expected", prog,
 			           Tnum, rules, type);
@@ -3688,8 +3788,8 @@ parentheses around an expression converts it into a Term,
 
 	case Concat:
 		/* both must be Tstr, result is Tstr */
-		propagate_types(b->left, c, ok, Tstr, 0);
-		propagate_types(b->right, c, ok, Tstr, 0);
+		propagate_types(b->left, c, perr, Tstr, 0);
+		propagate_types(b->right, c, perr, Tstr, 0);
 		if (!type_compat(type, Tstr, 0))
 			type_err(c, "error: Concat returns %1 but %2 expected", prog,
 			           Tstr, rules, type);
@@ -3697,7 +3797,7 @@ parentheses around an expression converts it into a Term,
 
 	case StringConv:
 		/* op must be string, result is number */
-		propagate_types(b->left, c, ok, Tstr, 0);
+		propagate_types(b->left, c, perr, Tstr, 0);
 		if (!type_compat(type, Tnum, 0))
 			type_err(c,	// UNTESTED
 			  "error: Can only convert string to number, not %1",
@@ -3705,7 +3805,7 @@ parentheses around an expression converts it into a Term,
 		return Tnum;
 
 	case Bracket:
-		return propagate_types(b->right, c, ok, type, 0);
+		return propagate_types(b->right, c, perr, type, 0);
 
 ###### interp binode cases
 
@@ -3972,7 +4072,7 @@ the common header for all reductions to use.
 		struct binode *e;
 
 		for (e = b; e; e = cast(binode, e->right)) {
-			t = propagate_types(e->left, c, ok, NULL, rules);
+			t = propagate_types(e->left, c, perr, NULL, rules);
 			if ((rules & Rboolok) && (t == Tbool || t == Tnone))
 				t = NULL;
 			if (t == Tnone && e->right)
@@ -4061,7 +4161,7 @@ printed.
 		else
 			b = cast(binode, b->right);
 		while (b) {
-			propagate_types(b->left, c, ok, NULL, Rnolabel);
+			propagate_types(b->left, c, perr, NULL, Rnolabel);
 			b = cast(binode, b->right);
 		}
 		break;
@@ -4178,23 +4278,23 @@ it is declared, and error will be raised as the name is created as
 		 * For Assign, left must not be constant.
 		 * result is Tnone
 		 */
-		t = propagate_types(b->left, c, ok, NULL,
+		t = propagate_types(b->left, c, perr, NULL,
 		                    Rnolabel | (b->op == Assign ? Rnoconstant : 0));
 		if (!b->right)
 			return Tnone;
 
 		if (t) {
-			if (propagate_types(b->right, c, ok, t, 0) != t)
+			if (propagate_types(b->right, c, perr, t, 0) != t)
 				if (b->left->type == Xvar)
 					type_err(c, "info: variable '%v' was set as %1 here.",
 					         cast(var, b->left)->var->where_set, t, rules, NULL);
 		} else {
-			t = propagate_types(b->right, c, ok, NULL, Rnolabel);
+			t = propagate_types(b->right, c, perr, NULL, Rnolabel);
 			if (t)
-				propagate_types(b->left, c, ok, t,
+				propagate_types(b->left, c, perr, t,
 				                (b->op == Assign ? Rnoconstant : 0));
 		}
-		if (t && t->dup == NULL && t->name.txt[0] != ' ') // HACK
+		if (t && t->dup == NULL && !(*perr & Emaycopy))
 			type_err(c, "error: cannot assign value of type %1", b, t, 0, NULL);
 		return Tnone;
 
@@ -4268,7 +4368,7 @@ function which has a return type, and the "condition" code blocks in
 
 	case Use:
 		/* result matches value */
-		return propagate_types(b->right, c, ok, type, 0);
+		return propagate_types(b->right, c, perr, type, 0);
 
 ###### interp binode cases
 
@@ -4655,10 +4755,10 @@ casepart` to track a list of case parts.
 
 ###### propagate binode cases
 	case Loop:
-		t = propagate_types(b->right, c, ok, Tnone, 0);
+		t = propagate_types(b->right, c, perr, Tnone, 0);
 		if (!type_compat(Tnone, t, 0))
-			*ok = 0;	// UNTESTED
-		return propagate_types(b->left, c, ok, type, rules);
+			*perr |= Efail;	// UNTESTED
+		return propagate_types(b->left, c, perr, type, rules);
 
 ###### propagate exec cases
 	case Xcond_statement:
@@ -4676,51 +4776,51 @@ casepart` to track a list of case parts.
 		struct cond_statement *cs = cast(cond_statement, prog);
 		struct casepart *cp;
 
-		t = propagate_types(cs->forpart, c, ok, Tnone, 0);
+		t = propagate_types(cs->forpart, c, perr, Tnone, 0);
 		if (!type_compat(Tnone, t, 0))
-			*ok = 0;	// UNTESTED
+			*perr |= Efail;	// UNTESTED
 
 		if (cs->looppart) {
-			t = propagate_types(cs->thenpart, c, ok, Tnone, 0);
+			t = propagate_types(cs->thenpart, c, perr, Tnone, 0);
 			if (!type_compat(Tnone, t, 0))
-				*ok = 0;	// UNTESTED
+				*perr |= Efail;	// UNTESTED
 		}
 		if (cs->casepart == NULL) {
-			propagate_types(cs->condpart, c, ok, Tbool, 0);
-			propagate_types(cs->looppart, c, ok, Tbool, 0);
+			propagate_types(cs->condpart, c, perr, Tbool, 0);
+			propagate_types(cs->looppart, c, perr, Tbool, 0);
 		} else {
 			/* Condpart must match case values, with bool permitted */
 			t = NULL;
 			for (cp = cs->casepart;
 			     cp && !t; cp = cp->next)
-				t = propagate_types(cp->value, c, ok, NULL, 0);
+				t = propagate_types(cp->value, c, perr, NULL, 0);
 			if (!t && cs->condpart)
-				t = propagate_types(cs->condpart, c, ok, NULL, Rboolok);	// UNTESTED
+				t = propagate_types(cs->condpart, c, perr, NULL, Rboolok);	// UNTESTED
 			if (!t && cs->looppart)
-				t = propagate_types(cs->looppart, c, ok, NULL, Rboolok);	// UNTESTED
+				t = propagate_types(cs->looppart, c, perr, NULL, Rboolok);	// UNTESTED
 			// Now we have a type (I hope) push it down
 			if (t) {
 				for (cp = cs->casepart; cp; cp = cp->next)
-					propagate_types(cp->value, c, ok, t, 0);
-				propagate_types(cs->condpart, c, ok, t, Rboolok);
-				propagate_types(cs->looppart, c, ok, t, Rboolok);
+					propagate_types(cp->value, c, perr, t, 0);
+				propagate_types(cs->condpart, c, perr, t, Rboolok);
+				propagate_types(cs->looppart, c, perr, t, Rboolok);
 			}
 		}
 		// (if)then, else, and case parts must return expected type.
 		if (!cs->looppart && !type)
-			type = propagate_types(cs->thenpart, c, ok, NULL, rules);
+			type = propagate_types(cs->thenpart, c, perr, NULL, rules);
 		if (!type)
-			type = propagate_types(cs->elsepart, c, ok, NULL, rules);
+			type = propagate_types(cs->elsepart, c, perr, NULL, rules);
 		for (cp = cs->casepart;
 		     cp && !type;
 		     cp = cp->next)	// UNTESTED
-			type = propagate_types(cp->action, c, ok, NULL, rules);	// UNTESTED
+			type = propagate_types(cp->action, c, perr, NULL, rules);	// UNTESTED
 		if (type) {
 			if (!cs->looppart)
-				propagate_types(cs->thenpart, c, ok, type, rules);
-			propagate_types(cs->elsepart, c, ok, type, rules);
+				propagate_types(cs->thenpart, c, perr, type, rules);
+			propagate_types(cs->elsepart, c, perr, type, rules);
 			for (cp = cs->casepart; cp ; cp = cp->next)
-				propagate_types(cp->action, c, ok, type, rules);
+				propagate_types(cp->action, c, perr, type, rules);
 			return type;
 		} else
 			return NULL;
@@ -4825,13 +4925,15 @@ various declarations in the parse context.
 
 ### The `const` section
 
-As well as being defined in with the code that uses them, constants
-can be declared at the top level.  These have full-file scope, so they
-are always `InScope`.  The value of a top level constant can be given
-as an expression, and this is evaluated immediately rather than in the
-later interpretation stage.  Once we add functions to the language, we
-will need rules concern which, if any, can be used to define a top
-level constant.
+As well as being defined in with the code that uses them, constants can
+be declared at the top level.  These have full-file scope, so they are
+always `InScope`, even before(!) they have been declared.  The value of
+a top level constant can be given as an expression, and this is
+evaluated after parsing and before execution.
+
+A function call can be used to evaluate a constant, but it will not have
+access to any program state, once such statement becomes meaningful.
+e.g.  arguments and filesystem will not be visible.
 
 Constants are defined in a section that starts with the reserved word
 `const` and then has a block with a list of assignment statements.
@@ -4840,11 +4942,8 @@ make it clear that they are constants.  Type can also be given: if
 not, the type will be determined during analysis, as with other
 constants.
 
-As the types constants are inserted at the head of a list, printing
-them in the same order that they were read is not straight forward.
-We take a quadratic approach here and count the number of constants
-(variables of depth 0), then count down from there, each time
-searching through for the Nth constant for decreasing N.
+###### parse context
+	struct binode *constlist;
 
 ###### top level grammar
 
@@ -4871,69 +4970,119 @@ searching through for the Nth constant for decreasing N.
 
 	$void
 	Const -> IDENTIFIER :: CType = Expression ${ {
-		int ok;
 		struct variable *v;
+		struct binode *bl, *bv;
+		struct var *var = new_pos(var, $ID);
 
-		v = var_decl(c, $1.txt);
+		v = var_decl(c, $ID.txt);
 		if (v) {
-			struct var *var = new_pos(var, $1);
 			v->where_decl = var;
 			v->where_set = var;
-			var->var = v;
+			v->type = $<CT;
 			v->constant = 1;
 			v->global = 1;
 		} else {
-			struct variable *vorig = var_ref(c, $1.txt);
-			tok_err(c, "error: name already declared", &$1);
-			type_err(c, "info: this is where '%v' was first declared",
-			         vorig->where_decl, NULL, 0, NULL);
-		}
-		do {
-			ok = 1;
-			propagate_types($5, c, &ok, $3, 0);
-		} while (ok == 2);
-		if (!ok)
-			c->parse_error = 1;
-		else if (v) {
-			struct value res = interp_exec(c, $5, &v->type);
-			global_alloc(c, v->type, v, &res);
+			v = var_ref(c, $1.txt);
+			if (v->type == Tnone) {
+				v->where_decl = var;
+				v->where_set = var;
+				v->type = $<CT;
+				v->constant = 1;
+				v->global = 1;
+			} else {
+				tok_err(c, "error: name already declared", &$1);
+				type_err(c, "info: this is where '%v' was first declared",
+				         v->where_decl, NULL, 0, NULL);
+			}
 		}
+		var->var = v;
+
+		bv = new(binode);
+		bv->op = Declare;
+		bv->left = var;
+		bv->right= $<Exp;
+
+		bl = new(binode);
+		bl->op = List;
+		bl->left = c->constlist;
+		bl->right = bv;
+		c->constlist = bl;
 	} }$
 
-###### print const decls
+###### core functions
+	static void resolve_consts(struct parse_context *c)
 	{
-		struct variable *v;
-		int target = -1;
-
-		while (target != 0) {
-			int i = 0;
-			for (v = context.in_scope; v; v=v->in_scope)
-				if (v->depth == 0 && v->constant) {
-					i += 1;
-					if (i == target)
-						break;
+		struct binode *b;
+		int retry = 1;
+		enum { none, some, cannot } progress = none;
+
+		c->constlist = reorder_bilist(c->constlist);
+		while (retry) {
+			retry = 0;
+			for (b = cast(binode, c->constlist); b;
+			     b = cast(binode, b->right)) {
+				enum prop_err perr;
+				struct binode *vb = cast(binode, b->left);
+				struct var *v = cast(var, vb->left);
+				if (v->var->frame_pos >= 0)
+					continue;
+				do {
+					perr = 0;
+					propagate_types(vb->right, c, &perr,
+						        v->var->type, 0);
+				} while (perr & Eretry);
+				if (perr & Efail)
+					c->parse_error += 1;
+				else if (!(perr & Enoconst)) {
+					progress = some;
+					struct value res = interp_exec(
+						c, vb->right, &v->var->type);
+					global_alloc(c, v->var->type, v->var, &res);
+				} else {
+					if (progress == cannot)
+						type_err(c, "error: const %v cannot be resolved.",
+							 v, NULL, 0, NULL);
+					else
+						retry = 1;
 				}
-
-			if (target == -1) {
-				if (i)
-					printf("const\n");
-				target = i;
-			} else {
-				struct value *val = var_value(&context, v);
-				printf("    %.*s :: ", v->name->name.len, v->name->name.txt);
-				type_print(v->type, stdout);
-				printf(" = ");
-				if (v->type == Tstr)
-					printf("\"");
-				print_value(v->type, val, stdout);
-				if (v->type == Tstr)
-					printf("\"");
-				printf("\n");
-				target -= 1;
+			}
+			switch (progress) {
+			case cannot:
+				retry = 0; break;
+			case none:
+				progress = cannot; break;
+			case some:
+				progress = none; break;
 			}
 		}
 	}
 
+###### print const decls
+	{
+		struct binode *b;
+		int first = 1;
+
+		for (b = cast(binode, context.constlist); b;
+		     b = cast(binode, b->right)) {
+			struct binode *vb = cast(binode, b->left);
+			struct var *vr = cast(var, vb->left);
+			struct variable *v = vr->var;
+
+			if (first)
+				printf("const\n");
+			first = 0;
+
+			printf("    %.*s :: ", v->name->name.len, v->name->name.txt);
+			type_print(v->type, stdout);
+			printf(" = ");
+			print_exec(vb->right, -1, 0);
+			printf("\n");
+		}
+	}
+
+###### free const decls
+	free_binode(context.constlist);
+
 ### Function declarations
 
 The code in an Ocean program is all stored in function declarations.
@@ -4954,7 +5103,7 @@ is a bit more interesting at this level.
 		 * is a list for 'struct var'
 		 */
 		struct type *t = add_anon_type(c, &structure_prototype,
-					       " function result");
+					       "function result");
 		int cnt = 0;
 		struct binode *b;
 
@@ -5088,20 +5237,20 @@ is a bit more interesting at this level.
 		for (v = c->in_scope; v; v = v->in_scope) {
 			struct value *val;
 			struct type *ret;
-			int ok = 1;
+			enum prop_err perr;
 			if (v->depth != 0 || !v->type || !v->type->check_args)
 				continue;
 			ret = v->type->function.inline_result ?
 				Tnone : v->type->function.return_type;
 			val = var_value(c, v);
 			do {
-				ok = 1;
-				propagate_types(val->function, c, &ok, ret, 0);
-			} while (ok == 2);
-			if (ok)
+				perr = 0;
+				propagate_types(val->function, c, &perr, ret, 0);
+			} while (!(perr & Efail) && (perr & Eretry));
+			if (!(perr & Efail))
 				/* Make sure everything is still consistent */
-				propagate_types(val->function, c, &ok, ret, 0);
-			if (!ok)
+				propagate_types(val->function, c, &perr, ret, 0);
+			if (perr & Efail)
 				all_ok = 0;
 			if (!v->type->function.inline_result &&
 			    !v->type->function.return_type->dup) {
@@ -5118,7 +5267,7 @@ is a bit more interesting at this level.
 	{
 		struct binode *bp = type->function.params;
 		struct binode *b;
-		int ok = 1;
+		enum prop_err perr;
 		int arg = 0;
 		struct type *argv_type;
 
@@ -5127,16 +5276,16 @@ is a bit more interesting at this level.
 		argv_type->array.unspec = 1;
 
 		for (b = bp; b; b = cast(binode, b->right)) {
-			ok = 1;
+			perr = 0;
 			switch (arg++) {
 			case 0: /* argv */
-				propagate_types(b->left, c, &ok, argv_type, 0);
+				propagate_types(b->left, c, &perr, argv_type, 0);
 				break;
 			default: /* invalid */	// NOTEST
-				propagate_types(b->left, c, &ok, Tnone, 0);	// NOTEST
+				propagate_types(b->left, c, &perr, Tnone, 0);	// NOTEST
 			}
-			if (!ok)
-				c->parse_error = 1;
+			if (perr & Efail)
+				c->parse_error += 1;
 		}
 
 		return !c->parse_error;
@@ -5157,12 +5306,12 @@ is a bit more interesting at this level.
 			progp = var_value(c, mainv);
 		if (!progp || !progp->function) {
 			fprintf(stderr, "oceani: no main function found.\n");
-			c->parse_error = 1;
+			c->parse_error += 1;
 			return;
 		}
 		if (!analyse_main(mainv->type, c)) {
 			fprintf(stderr, "oceani: main has wrong type.\n");
-			c->parse_error = 1;
+			c->parse_error += 1;
 			return;
 		}
 		al = mainv->type->function.params;