compilation

src/parser.h

@@ -1,7 +1,6 @@
 #pragma once
 
-#include <sstream>
-#include <string>
+#include <istream>
 #include <vector>
 
 struct Expr {
@@ -20,19 +19,19 @@ public:
       if (child.type == Type::List && child.children.size() >= 2 &&
           child.children[0].type == Type::Atom &&
           child.children[0].value == key) {
-        return child.children[1];
+        Expr result = {.type = Type::List};
+        result.children.assign(child.children.begin() + 1,
+                               child.children.end());
+        return result;
       }
     }
     throw std::runtime_error("key not found: " + key);
   }
 
-  static Expr parse(const std::string &input) {
-    std::istringstream in(input);
-    return parse_expr(in);
-  }
+  static Expr parse(std::istream &in) { return parse_expr(in); }
 
 private:
-  static std::string read_atom(std::istringstream &in) {
+  static std::string read_atom(std::istream &in) {
     std::string atom;
     while (true) {
       int next = in.peek();
@@ -48,7 +47,7 @@ private:
     return atom;
   }
 
-  static Expr parse_list(std::istringstream &in) {
+  static Expr parse_list(std::istream &in) {
     Expr result = {.type = Expr::Type::List};
 
     in.get(); // consume bracket
@@ -72,7 +71,7 @@ private:
     return result;
   }
 
-  static std::string read_string(std::istringstream &in) {
+  static std::string read_string(std::istream &in) {
     std::string result;
 
     in.get(); // consume the quote
@@ -91,7 +90,7 @@ private:
     return result;
   }
 
-  static Expr parse_expr(std::istringstream &in) {
+  static Expr parse_expr(std::istream &in) {
     while (is_space(static_cast<char>(in.peek()))) {
       in.get();
     }
@@ -138,4 +137,4 @@ inline std::ostream &operator<<(std::ostream &out, const Expr &e) {
     break;
   }
   return out;
-}
+}