hare

commit 8fd2614695b0d216e0e773b9e6bbd61b3026c4d8
parent 4b064c0a701a7139b6e883327d959ce2d5b38fd1
Author: Drew DeVault <sir@cmpwn.com>
Date:   Sun, 18 Apr 2021 08:10:27 -0400

hare::parse: implement for loops

Diffstat:
M
hare/parse/+test/expr.ha
 | 
21
+++++++++++++++++++++
M
hare/parse/expr.ha
 | 
50
+++++++++++++++++++++++++++++++++++++++++++++++---
M
hare/unparse/expr.ha
 | 
27
++++++++++++++++++++++++++-

3 files changed, 94 insertions(+), 4 deletions(-)
diff --git a/hare/parse/+test/expr.ha b/hare/parse/+test/expr.ha
@@ -54,6 +54,27 @@
 ");
 };
 
+@test fn for_expr() void = {
+	roundtrip("export fn main() void = {
+	for (true) {
+		x;
+	};
+	:label for (true) {
+		x;
+	};
+	for (let x = 0; x < 10) {
+		x;
+	};
+	for (x < 10; x) {
+		x;
+	};
+	for (let x = 10; x < 10; x) {
+		x;
+	};
+};
+");
+};
+
 @test fn if_expr() void = {
 	roundtrip("export fn main() void = {
 	if (x == y) {
diff --git a/hare/parse/expr.ha b/hare/parse/expr.ha
@@ -6,8 +6,8 @@ use fmt;
 // Parses an expression.
 export fn expression(lexer: *lex::lexer) (ast::expr | error) = {
 	const tok = match (peek(lexer, ltok::LBRACE, ltok::MATCH, ltok::SWITCH,
-			ltok::IF, ltok::FOR, ltok::BREAK, ltok::CONTINUE,
-			ltok::RETURN, ltok::LET, ltok::CONST)?) {
+			ltok::IF, ltok::LABEL, ltok::FOR, ltok::BREAK,
+			ltok::CONTINUE, ltok::RETURN, ltok::LET, ltok::CONST)?) {
 		void => return binarithm(lexer, void, 0),
 		tok: lex::token => tok,
 	};
@@ -16,7 +16,7 @@ export fn expression(lexer: *lex::lexer) (ast::expr | error) = {
 		ltok::MATCH => abort(), // TODO
 		ltok::SWITCH => abort(), // TODO
 		ltok::IF => if_expr(lexer),
-		ltok::FOR => abort(), // TODO
+		ltok::LABEL, ltok::FOR => for_expr(lexer),
 		ltok::BREAK, ltok::CONTINUE, ltok::RETURN => control(lexer),
 		ltok::LET, ltok::CONST => binding(lexer, false),
 		* => abort(), // Invariant
@@ -237,6 +237,50 @@ fn expression_list(lexer: *lex::lexer) (ast::expr | error) = {
 	return items;
 };
 
+fn for_expr(lexer: *lex::lexer) (ast::expr | error) = {
+	let tok = want(lexer, ltok::FOR, ltok::LABEL)?;
+	let label: ast::label = switch (tok.0) {
+		ltok::LABEL => {
+			want(lexer, ltok::FOR)?;
+			tok.1 as str;
+		},
+		* => "",
+	};
+
+	want(lexer, ltok::LPAREN)?;
+
+	let bindings: nullable *ast::expr = match (peek(
+			lexer, ltok::LET, ltok::CONST)?) {
+		void => null,
+		lex::token => {
+			let bindings = alloc(binding(lexer, false)?);
+			want(lexer, ltok::SEMICOLON)?;
+			bindings;
+		},
+	};
+
+	let cond = alloc(expression(lexer)?);
+
+	let afterthought: nullable *ast::expr = match (peek(
+			lexer, ltok::SEMICOLON)) {
+		void => null,
+		lex::token => {
+			want(lexer, ltok::SEMICOLON)?;
+			alloc(expression(lexer)?);
+		},
+	};
+
+	want(lexer, ltok::RPAREN)?;
+
+	return ast::for_expr {
+		label = label,
+		bindings = bindings,
+		cond = cond,
+		afterthought = afterthought,
+		body = alloc(expression(lexer)?),
+	};
+};
+
 fn if_expr(lexer: *lex::lexer) (ast::expr | error) = {
 	want(lexer, ltok::IF)?;
 	want(lexer, ltok::LPAREN)?;
diff --git a/hare/unparse/expr.ha b/hare/unparse/expr.ha
@@ -123,7 +123,7 @@ export fn expr(
 		},
 		e: ast::defer_expr => abort(),
 		e: ast::delete_expr => abort(),
-		e: ast::for_expr => abort(),
+		e: ast::for_expr => for_expr(out, indent, e)?,
 		e: ast::free_expr => abort(),
 		e: ast::if_expr => {
 			let z = fmt::fprint(out, "if (")?;
@@ -240,3 +240,28 @@ fn constant(
 		},
 	};
 };
+
+fn for_expr(
+	out: *io::stream,
+	indent: size,
+	e: ast::for_expr,
+) (size | io::error) = {
+	let z = 0z;
+	if (e.label != "") {
+		z += fmt::fprintf(out, ":{} ", e.label)?;
+	};
+	z += fmt::fprintf(out, "for (")?;
+	z += match (e.bindings) {
+		null => 0z,
+		e: *ast::expr => expr(out, indent, *e)?
+			+ fmt::fprint(out, "; ")?,
+	};
+	z += expr(out, indent, *e.cond)?;
+	z += match (e.afterthought) {
+		null => 0z,
+		e: *ast::expr => fmt::fprint(out, "; ")?
+			+ expr(out, indent, *e)?,
+	};
+	z += fmt::fprintf(out, ") ")?;
+	return z + expr(out, indent, *e.body)?;
+};