From 9a2f89b1a0846809c6855814a8f72e8fa74f0e43 Mon Sep 17 00:00:00 2001
From: NeilBrown <neil@brown.name>
Date: Sun, 3 Oct 2021 09:36:50 +1100
Subject: [PATCH] ocean: introduce prefix op for string->number conversion.

Rather than having magic conversion of command line args to numbers as
needed, introduce '$' as a prefix op to to the conversion.
This is a step towards changing 'program' to be a 'main' function.

Signed-off-by: NeilBrown <neil@brown.name>
---
 csrc/oceani-tests.mdc |  3 ++-
 csrc/oceani.mdc       | 49 +++++++++++++++++++++++++++++++++----------
 2 files changed, 40 insertions(+), 12 deletions(-)

diff --git a/csrc/oceani-tests.mdc b/csrc/oceani-tests.mdc
index e3739ed..5e91192 100644
--- a/csrc/oceani-tests.mdc
+++ b/csrc/oceani-tests.mdc
@@ -282,7 +282,8 @@ Here I break it into two parts, keeping the array code separate.
 
 ###### test: sayhello
 
-	program A B astr bbool:
+	program As Bs astr bbool:
+		A := $As; B := $Bs
 		print "Hello World, what lovely oceans you have!"
 		/* When a variable is defined in both branches of an 'if',
 		 * and used afterwards, the variables are merged.
diff --git a/csrc/oceani.mdc b/csrc/oceani.mdc
index 520212b..d690b70 100644
--- a/csrc/oceani.mdc
+++ b/csrc/oceani.mdc
@@ -2772,9 +2772,14 @@ expression operator, and the `CMPop` non-terminal will match one of them.
 
 ### Expressions: The rest
 
-The remaining expressions with the highest precedence are arithmetic and
-string concatenation.  String concatenation (`++`) has the same
-precedence as multiplication and division, but lower than the uniary.
+The remaining expressions with the highest precedence are arithmetic,
+string concatenation, and string conversion.  String concatenation
+(`++`) has the same precedence as multiplication and division, but lower
+than the uniary.
+
+String conversion is a temporary feature until I get a better type
+system.  `$` is a prefix operator which expects a string and returns
+a number.
 
 `+` and `-` are both infix and prefix operations (where they are
 absolute value and negation).  These have different operator names.
@@ -2788,12 +2793,13 @@ should only insert brackets were needed for precedence.
 	Times, Divide, Rem,
 	Concat,
 	Absolute, Negate,
+	StringConv,
 	Bracket,
 
 ###### expr precedence
 	$LEFT + - Eop
 	$LEFT * / % ++ Top
-	$LEFT Uop
+	$LEFT Uop $
 	$TERM ( )
 
 ###### expression grammar
@@ -2834,6 +2840,7 @@ should only insert brackets were needed for precedence.
 
 	Uop ->    + ${ $0.op = Absolute; }$
 		| - ${ $0.op = Negate; }$
+		| $ ${ $0.op = StringConv; }$
 
 	Top ->    * ${ $0.op = Times; }$
 		| / ${ $0.op = Divide; }$
@@ -2862,14 +2869,15 @@ should only insert brackets were needed for precedence.
 		if (bracket) printf(")");
 		break;
 	case Absolute:
-		if (bracket) printf("(");
-		printf("+");
-		print_exec(b->right, indent, bracket);
-		if (bracket) printf(")");
-		break;
 	case Negate:
+	case StringConv:
 		if (bracket) printf("(");
-		printf("-");
+		switch (b->op) {
+		case Absolute:   fputs("+", stdout); break;
+		case Negate:     fputs("-", stdout); break;
+		case StringConv: fputs("$", stdout); break;
+		default: abort();	// NOTEST
+		}			// NOTEST
 		print_exec(b->right, indent, bracket);
 		if (bracket) printf(")");
 		break;
@@ -2906,6 +2914,15 @@ should only insert brackets were needed for precedence.
 			           Tstr, rules, type);
 		return Tstr;
 
+	case StringConv:
+		/* op must be string, result is number */
+		propagate_types(b->left, c, ok, Tstr, 0);
+		if (!type_compat(type, Tnum, 0))
+			type_err(c,
+			  "error: Can only convert string to number, not %1",
+				prog, type, 0, NULL);
+		return Tnum;
+
 	case Bracket:
 		return propagate_types(b->right, c, ok, type, 0);
 
@@ -2963,6 +2980,14 @@ should only insert brackets were needed for precedence.
 		rvtype = Tstr;
 		rv.str = text_join(left.str, right.str);
 		break;
+	case StringConv:
+		right = interp_exec(b->right, &rvtype);
+		rtype = Tstr;
+		rvtype = Tnum;
+		char *str = strndup(right.str.txt, right.str.len);
+		parse_value(rvtype, str, &rv);
+		free(str);
+		break;
 
 ###### value functions
 
@@ -4248,11 +4273,13 @@ things which will likely grow as the languages grows.
 		name:string
 		alive:Boolean
 
-	program A B:
+	program Astr Bstr:
 		print "Hello World, what lovely oceans you have!"
 		print "Are there", five, "?"
 		print pi, pie, "but", cake
 
+		A := $Astr; B := $Bstr
+
 		/* When a variable is defined in both branches of an 'if',
 		 * and used afterwards, the variables are merged.
 		 */
-- 
2.43.0