From: NeilBrown <neil@brown.name>
Date: Sun, 28 Apr 2019 00:40:12 +0000 (+1000)
Subject: oceani: allow a variable to be declared with no value
X-Git-Tag: JamisonCreek-3~38
X-Git-Url: https://ocean-lang.org/code/?p=ocean;a=commitdiff_plain;h=2770ad454dcc49b478e5452dfda69803c8f94c69

oceani: allow a variable to be declared with no value

 var:type

is now allowed.  "var:" is not - there must be either a
type or an initial value.

If only the type is given, the type's 'init' function
is called to provide an initial value.

Signed-off-by: NeilBrown <neil@brown.name>
---

diff --git a/csrc/oceani.mdc b/csrc/oceani.mdc
index df9a5c5..2be4d5d 100644
--- a/csrc/oceani.mdc
+++ b/csrc/oceani.mdc
@@ -1589,7 +1589,7 @@ link to find the primary instance.
 ###### Grammar
 
 	$*var
-	VariableDecl -> IDENTIFIER : = ${ {
+	VariableDecl -> IDENTIFIER : ${ {
 		struct variable *v = var_decl(config2context(config), $1.txt);
 		$0 = new_pos(var, $1);
 		$0->var = v;
@@ -1604,7 +1604,7 @@ link to find the primary instance.
 			         v->where_decl, Tnone, 0, Tnone);
 		}
 	} }$
-	    | IDENTIFIER :: = ${ {
+	    | IDENTIFIER :: ${ {
 		struct variable *v = var_decl(config2context(config), $1.txt);
 		$0 = new_pos(var, $1);
 		$0->var = v;
@@ -1620,7 +1620,7 @@ link to find the primary instance.
 			         v->where_decl, Tnone, 0, Tnone);
 		}
 	} }$
-	    | IDENTIFIER : Type = ${ {
+	    | IDENTIFIER : Type ${ {
 		struct variable *v = var_decl(config2context(config), $1.txt);
 		$0 = new_pos(var, $1);
 		$0->var = v;
@@ -1637,7 +1637,7 @@ link to find the primary instance.
 			         v->where_decl, Tnone, 0, Tnone);
 		}
 	} }$
-	    | IDENTIFIER :: Type = ${ {
+	    | IDENTIFIER :: Type ${ {
 		struct variable *v = var_decl(config2context(config), $1.txt);
 		$0 = new_pos(var, $1);
 		$0->var = v;
@@ -2456,11 +2456,23 @@ it is declared, and error will be raised as the name is created as
 				         v->var->where_decl, NULL, 0, NULL);
 			}
 		} }$
-	| VariableDecl Expression ${
+	| VariableDecl = Expression ${
 			$0 = new(binode);
 			$0->op = Declare;
 			$0->left = $<1;
-			$0->right =$<2;
+			$0->right =$<3;
+		}$
+
+	| VariableDecl ${
+			if ($1->var->where_set == NULL) {
+				type_err(config2context(config), "Variable declared with no type or value: %v",
+				         $1, NULL, 0, NULL);
+			} else {
+				$0 = new(binode);
+				$0->op = Declare;
+				$0->left = $<1;
+				$0->right = NULL;
+			}
 		}$
 
 ###### print binode cases
@@ -2481,18 +2493,21 @@ it is declared, and error will be raised as the name is created as
 		print_exec(b->left, indent, 0);
 		if (cast(var, b->left)->var->constant) {
 			if (v->where_decl == v->where_set)
-				printf("::%.*s = ", v->val.type->name.len,
+				printf("::%.*s ", v->val.type->name.len,
 				       v->val.type->name.txt);
 			else
-				printf(" ::= ");
+				printf(" ::");
 		} else {
 			if (v->where_decl == v->where_set)
-				printf(":%.*s = ", v->val.type->name.len,
+				printf(":%.*s ", v->val.type->name.len,
 				       v->val.type->name.txt);
 			else
-				printf(" := ");
+				printf(" :");
+		}
+		if (b->right) {
+			printf("= ");
+			print_exec(b->right, indent, 0);
 		}
-		print_exec(b->right, indent, 0);
 		if (indent >= 0)
 			printf("\n");
 		}
@@ -2504,6 +2519,9 @@ it is declared, and error will be raised as the name is created as
 	case Declare:
 		/* Both must match and not be labels, result is Tnone */
 		t = propagate_types(b->left, c, ok, NULL, Rnolabel);
+		if (!b->right)
+			return Tnone;
+
 		if (t) {
 			if (propagate_types(b->right, c, ok, t, 0) != t)
 				if (b->left->type == Xvar)
@@ -2521,7 +2539,6 @@ it is declared, and error will be raised as the name is created as
 ###### interp binode cases
 
 	case Assign:
-	case Declare:
 	{
 		struct variable *v = cast(var, b->left)->var;
 		if (v->merged)
@@ -2533,6 +2550,21 @@ it is declared, and error will be raised as the name is created as
 		break;
 	}
 
+	case Declare:
+	{
+		struct variable *v = cast(var, b->left)->var;
+		if (v->merged)
+			v = v->merged;
+		if (b->right)
+			right = interp_exec(b->right);
+		else
+			right = val_init(v->val.type);
+		free_value(v->val);
+		v->val = right;
+		right.type = NULL;
+		break;
+	}
+
 ### The `use` statement
 
 The `use` statement is the last "simple" statement.  It is needed when
@@ -3216,7 +3248,8 @@ Fibonacci, and performs a binary search for a number.
 			double := A*2
 			print "double", A, "is only", double
 
-		a := A;
+		a : number
+		a = A;
 		b:number = B
 		if a > 0 and b > 0:
 			while a != b: