From a50a3bceb3c7f8825cc4d6b12599918e465388ff Mon Sep 17 00:00:00 2001
From: VaclavT <vaclavt@gmail.com>
Date: Wed, 14 Apr 2021 07:55:55 +0200
Subject: [PATCH] set! added

---
 ml.cpp | 28 ++++++++++++++++++++++++++++
 ml.h   |  4 ++++
 2 files changed, 32 insertions(+)

diff --git a/ml.cpp b/ml.cpp
index 3c2294d..c183af1 100644
--- a/ml.cpp
+++ b/ml.cpp
@@ -652,6 +652,22 @@ void MlEnvironment::set(const std::string &name, MlValue value) {
 }
 
 
+void MlEnvironment::setX(const std::string &name, MlValue value) {
+	MlEnvironment* e = this;	
+	do {
+		std::map<std::string, MlValue>::const_iterator itr = e->defs.find(name);
+		if (itr != e->defs.end()) {
+			e->set(name, value);
+			return;
+		}
+		e = e->parent_scope;
+	} while (e != nullptr);
+
+	// not found so define
+	this->set(name, value);
+}
+
+
 MlValue MlValue::apply(std::vector<MlValue> args, MlEnvironment &env) {
 	MlEnvironment e;
 	std::vector<MlValue> params;
@@ -936,6 +952,16 @@ namespace builtin {
 	    return f;
     }
 
+    // Sets (if exists) or define a variable with a value (SPECIAL FORM)
+    MlValue setx(std::vector<MlValue> args, MlEnvironment &env) {
+	    if (args.size() != 2)
+		    throw MlError(MlValue("set!", define), env, args.size() > 2 ? TOO_MANY_ARGS : TOO_FEW_ARGS);
+
+	    MlValue result = args[1].eval(env);
+	    env.setX(args[0].display(), result);
+	    return result;
+    }
+
     // Loop over a list of expressions with a condition (SPECIAL FORM)
     MlValue while_loop(std::vector<MlValue> args, MlEnvironment &env) {
 	    MlValue acc;
@@ -1796,6 +1822,7 @@ MlValue MlEnvironment::get(const std::string &name) const {
 	if (name == "benchmark") return MlValue("benchmark", builtin::benchmark);
 	if (name == "and") return MlValue("and", builtin::do_and);
 	if (name == "or") return MlValue("or", builtin::do_or);
+	if (name == "set!") return MlValue("set!", builtin::setx);
 
 	// Comparison operations
 	if (name == "=") return MlValue("=", builtin::eq);
@@ -1976,3 +2003,4 @@ int main(int argc, char *argv[]) {
 
 	return 1;
 }
+
diff --git a/ml.h b/ml.h
index f5e5cd0..45faf33 100644
--- a/ml.h
+++ b/ml.h
@@ -42,6 +42,10 @@ public:
     // Set the value associated with this name in this scope
     void set(const std::string &name, MlValue value);
 
+    // Set the value associated with this name in this scope and parent scopes
+    // and if not exists sets in this scope
+    void setX(const std::string &name, MlValue value);
+
     // Get vector of executables in this scope
     std::vector<std::string> get_lambdas_list() const;