From 4b606ddde48d77e17516373af8dc852df3b26651 Mon Sep 17 00:00:00 2001
From: NeilBrown <neil@brown.name>
Date: Mon, 13 May 2019 16:17:12 +1000
Subject: [PATCH] oceani: add the option for "const" sections

These are introduced with "const" and can define one or
more constants - on one line with ';' or multiple lines
with {} or :

Signed-off-by: NeilBrown <neil@brown.name>
---
 csrc/oceani-tests.mdc | 56 ++++++++++++++++++++++++++++++
 csrc/oceani.mdc       | 79 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 135 insertions(+)

diff --git a/csrc/oceani-tests.mdc b/csrc/oceani-tests.mdc
index a41b199..10a3b70 100644
--- a/csrc/oceani-tests.mdc
+++ b/csrc/oceani-tests.mdc
@@ -131,6 +131,29 @@ Next we change the value of variables
 ###### output: setvar
 	1.07374e+09 1
 
+Now some contants
+
+###### test list
+	oceani_tests += "consts"
+
+###### test: consts
+	const:
+		pi ::= 3.1415926
+		four ::= 2 + 2 ; five ::= 10/2
+	const pie ::= "I like Pie";
+		cake ::= "The cake is"
+		  ++ " a lie"
+
+	program:
+		print "Hello World, what lovely oceans you have!"
+		print "are there", five, "?"
+		print pi, pie, "but", cake
+
+###### output: consts
+	Hello World, what lovely oceans you have!
+	are there 5 ?
+	3.14159 I like Pie but The cake is a lie
+
 ## Conditions and Loops
 
 Now we need to test if/else and some different loops
@@ -646,6 +669,39 @@ various places that `type_err()` are called.
 	.tmp.code:3:14: info: this is where 'b' was set to label
 	oceani: type error in program - not running.
 
+###### test list
+	oceani_failing_tests += type_err_const type_err_const1
+
+###### test: type_err_const
+	const:
+		foo :: number = 45
+		bar ::= "string" + 56
+	const:
+		bar ::= "baz"
+	program:
+		foo := 4
+		print foo, bar
+
+###### output: type_err_const
+	.tmp.code:4:16: error: expected number found string
+	.tmp.code:6:8: error: name already declared: bar
+	.tmp.code:4:8: info: this is where 'bar' was first declared
+	.tmp.code:8:8: error: variable 'foo' redeclared
+	.tmp.code:3:8: info: this is where 'foo' was first declared
+
+###### test: type_err_const1
+	const:
+		foo : number = 45
+		bar := "string"
+	program:
+		foo := 4
+		print foo, bar
+
+###### output: type_err_const1
+	.tmp.code:3:12: error: unhandled parse error: :
+	oceani: no program found.
+
+
 ## Test erroneous command line args
 
 To improve coverage, we want to test correct handling of strange command
diff --git a/csrc/oceani.mdc b/csrc/oceani.mdc
index 48ce058..58d5d32 100644
--- a/csrc/oceani.mdc
+++ b/csrc/oceani.mdc
@@ -1081,6 +1081,8 @@ no longer be primary.
 
 			v = t->previous;
 			free_value(t->val);
+			if (t->min_depth == 0)
+				free_exec(t->where_decl);
 			free(t);
 		}
 	}
@@ -3574,6 +3576,73 @@ various declarations in the parse context.
 
 	## top level grammar
 
+### 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.
+
+Constants are defined in a sectiont that starts with the reserved word
+`const` and then has a block with a list of assignment statements.
+For syntactic consistency, these must use the double-colon syntax to
+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.
+
+###### top level grammar
+
+	DeclareConstant -> const Open ConstList Close
+		| const Open Newlines ConstList Close
+		| const Open SimpleConstList }
+		| const Open Newlines SimpleConstList }
+		| const : ConstList
+		| const SimpleConstList
+
+	ConstList -> ComplexConsts
+	ComplexConsts -> ComplexConst ComplexConsts
+		| ComplexConst
+	ComplexConst -> SimpleConstList NEWLINE
+	SimpleConstList -> Const ; SimpleConstList
+		| Const
+		| Const ; SimpleConstList ;
+
+	$*type
+	CType -> Type	${ $0 = $<1; }$
+		|	${ $0 = NULL; }$
+	$void
+	Const -> IDENTIFIER :: CType = Expression ${ {
+		int ok;
+		struct variable *v;
+
+		v = var_decl(config2context(config), $1.txt);
+		if (v) {
+			struct var *var = new_pos(var, $1);
+			v->where_decl = var;
+			v->where_set = var;
+			var->var = v;
+			v->constant = 1;
+		} else {
+			v = var_ref(config2context(config), $1.txt);
+			tok_err(config2context(config), "error: name already declared", &$1);
+			type_err(config2context(config), "info: this is where '%v' was first declared",
+			         v->where_decl, NULL, 0, NULL);
+		}
+		do {
+			ok = 1;
+			propagate_types($5, config2context(config), &ok, $3, 0);
+		} while (ok == 2);
+		if (!ok)
+			config2context(config)->parse_error = 1;
+		else if (v) {
+			v->val = interp_exec($5);
+		}
+	} }$
+
+
 ### Finally the whole program.
 
 Somewhat reminiscent of Pascal a (current) Ocean program starts with
@@ -3735,8 +3804,18 @@ Fibonacci, and performs a binary search for a number.
 
 ###### test: hello
 
+	const:
+		pi ::= 3.1415926
+		four ::= 2 + 2 ; five ::= 10/2
+	const pie ::= "I like Pie";
+		cake ::= "The cake is"
+		  ++ " a lie"
+
 	program A B:
 		print "Hello World, what lovely oceans you have!"
+		print "are there", five, "?"
+		print pi, pie, "but", cake
+
 		/* When a variable is defined in both branches of an 'if',
 		 * and used afterwards, the variables are merged.
 		 */
-- 
2.43.0