Implement "size" function in stdlib

src/common.cpp

@@ -391,6 +391,18 @@ Result<Value> Pair::rest() const {
   return Value::create(val);
 }
 
+Result<uint64_t> Pair::size() const {
+  uint64_t res = 1;
+
+  Value cur = TRY(rest());
+  while (!cur.is<Nil>()) {
+    res += 1;
+    cur = TRY(cur.rest());
+  }
+
+  return res;
+}
+
 Result<Value> Pair::get(const Value& key) const {
   if (!key.is<Int64>()) return ERROR(TypeMismatch);
 

src/common.hpp

@@ -161,6 +161,7 @@ class Nil : public Object {
   virtual Result<Value> copy_value() const final;
   Result<Nil> copy() const;
 
+  virtual Result<uint64_t> size() const { return 0; }
   virtual void move(Object* obj) final { new (obj) Nil(std::move(_value)); }
 
  private:
@@ -757,6 +758,8 @@ class Pair : public Object {
   Result<Value> third() const final;
   Result<Value> rest() const final;
 
+  virtual Result<uint64_t> size() const final;
+
   virtual Result<Value> copy_value() const final;
   Result<Pair> copy() const;
 
@@ -1273,6 +1276,7 @@ class Value {
   Result<Value> second() const { return ((Object*)buf)->second(); }
   Result<Value> third() const { return ((Object*)buf)->third(); }
   Result<Value> rest() const { return ((Object*)buf)->rest(); }
+  Result<uint64_t> size() const { return ((Object*)buf)->size(); }
 
   // TODO: cmp() probably doesn't need arena parameter
   // Result<bool> operator==(Value& rhs) { return TRY(cmp(rhs)) == 0; }

src/stdlib.cpp

@@ -128,6 +128,15 @@ Result<Value> stdlib_srcloc(const Array& params) {
   return Value(TRY(SrcLoc::create(sr)));
 }
 
+Result<Value> stdlib_size(const Array& params) {
+  auto size = TRY(params.size());
+  if (size != 1) return ERROR(ArgumentCountMismatch);
+  auto param = TRY(params.get(0));
+  auto psize = TRY(param.size());
+
+  return Value(TRY(Int64::create((int64_t)psize)));
+}
+
 #define STDLIB_FUNCTION(name, id)                                  \
   [(uint64_t)StdlibFunctionId::id] = {#name, StdlibFunctionId::id, \
                                       stdlib_##name}
@@ -143,6 +152,7 @@ static StdlibFunctionEntry function_entries[] = {
     STDLIB_FUNCTION(array, Array),
     STDLIB_FUNCTION(get, Get),
     STDLIB_FUNCTION(srcloc, SrcLoc),
+    STDLIB_FUNCTION(size, Size),
     [(uint64_t)StdlibFunctionId::Max] = {0, StdlibFunctionId::Max,
                                          stdlib_unknown},
 };

src/stdlib.hpp

@@ -15,6 +15,7 @@ enum class StdlibFunctionId : uint64_t {
   Array,
   Get,
   SrcLoc,
+  Size,
   Max,
 };