From a4635fb95235ba4bf077bd59957da0626fc5ba72 Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbarenblat@gmail.com>
Date: Tue, 14 Dec 2021 12:34:06 -0500
Subject: EC, a terminal-based RPN calculator

---
 src/language.cc | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 src/language.cc

(limited to 'src/language.cc')

diff --git a/src/language.cc b/src/language.cc
new file mode 100644
index 0000000..277c545
--- /dev/null
+++ b/src/language.cc
@@ -0,0 +1,95 @@
+// Copyright 2021 Benjamin Barenblat
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+#include "src/language.h"
+
+#include <stdint.h>
+
+#include <memory>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "src/builtin.h"
+#include "third_party/abseil/absl/strings/str_cat.h"
+
+namespace ec {
+
+State::State() noexcept : environment(BuiltinEnvironment()) {}
+
+void GroundTerm::Evaluate(State& state) const noexcept {
+  state.stack.push_back(Clone());
+}
+
+std::string GroundTerm::Show() const noexcept {
+  // A double-precision value has 13 decimal digits of precision.
+  std::ostringstream s;
+  s.precision(13);
+  s << value_;
+  return s.str();
+}
+
+std::string GroundTerm::DebugString() const noexcept {
+  return absl::StrCat("GroundTerm(", value_, ")");
+}
+
+GroundTerm* GroundTerm::CloneImpl() const noexcept {
+  return new GroundTerm(*this);
+}
+
+void ForeignProgramTerm::Evaluate(State& state) const { impl_(state); }
+
+std::string ForeignProgramTerm::Show() const noexcept { return "<program>"; }
+
+std::string ForeignProgramTerm::DebugString() const noexcept {
+  return absl::StrCat("ForeignProgramTerm(", reinterpret_cast<uintptr_t>(impl_),
+                      ")");
+}
+
+ForeignProgramTerm* ForeignProgramTerm::CloneImpl() const noexcept {
+  return new ForeignProgramTerm(*this);
+}
+
+void SymbolTerm::Evaluate(State& state) const {
+  auto it = state.environment.find(name_);
+  if (it == state.environment.end()) {
+    throw UndefinedName(name_);
+  }
+  it->second->Evaluate(state);
+}
+
+std::string SymbolTerm::Show() const noexcept {
+  return absl::StrCat("'", name_);
+}
+
+std::string SymbolTerm::DebugString() const noexcept {
+  return absl::StrCat("SymbolTerm(", name_, ")");
+}
+
+SymbolTerm* SymbolTerm::CloneImpl() const noexcept {
+  return new SymbolTerm(*this);
+}
+
+void FormatStackElement(std::string* out,
+                        std::shared_ptr<const Term> term) noexcept {
+  out->append(term->Show());
+}
+
+void EvaluateAll(const Program& program, State& state) {
+  for (auto term : program) {
+    term->Evaluate(state);
+  }
+}
+
+}  // namespace ec
-- 
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