Add lookup expressions

blueprintcompiler/language/expression.py

@@ -0,0 +1,63 @@
+# expressions.py
+#
+# Copyright 2022 James Westman <james@jwestman.net>
+#
+# This file is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as
+# published by the Free Software Foundation; either version 3 of the
+# License, or (at your option) any later version.
+#
+# This file is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# SPDX-License-Identifier: LGPL-3.0-or-later
+
+
+from .common import *
+
+
+expr = Pratt()
+
+
+class Expr(AstNode):
+    grammar = expr
+
+    def emit_xml(self, xml: XmlEmitter):
+        self.children[-1].emit_xml(xml)
+
+
+class InfixExpr(AstNode):
+    @property
+    def lhs(self):
+        children = list(self.parent_by_type(Expr).children)
+        return children[children.index(self) - 1]
+
+
+class IdentExpr(AstNode):
+    grammar = UseIdent("ident")
+
+    def emit_xml(self, xml: XmlEmitter):
+        xml.start_tag("constant")
+        xml.put_text(self.tokens["ident"])
+        xml.end_tag()
+
+
+class LookupOp(InfixExpr):
+    grammar = [".", UseIdent("property")]
+
+    def emit_xml(self, xml: XmlEmitter):
+        xml.start_tag("lookup", name=self.tokens["property"])
+        self.lhs.emit_xml(xml)
+        xml.end_tag()
+
+
+expr.children = [
+    Prefix(IdentExpr),
+    Prefix(["(", Expr, ")"]),
+    Infix(10, LookupOp),
+]