Added support for value expression definitions.

Example:

  ] expr f(x) := x + 100
  ] expr f(100)
  200

src/op.cc

@@ -36,7 +36,7 @@ namespace ledger {
 
 expr_t::ptr_op_t expr_t::op_t::compile(scope_t& scope)
 {
-  if (kind == IDENT) {
+  if (is_ident()) {
     DEBUG("expr.compile", "Looking up identifier '" << as_ident() << "'");
 
     if (ptr_op_t def = scope.lookup(as_ident())) {
@@ -58,6 +58,23 @@ expr_t::ptr_op_t expr_t::op_t::compile(scope_t& scope)
   if (kind < TERMINALS)
     return this;
 
+  if (kind == O_DEFINE) {
+    switch (left()->kind) {
+    case IDENT:
+      scope.define(left()->as_ident(), right());
+      break;
+    case O_CALL:
+      if (left()->left()->is_ident())
+	scope.define(left()->left()->as_ident(), this);
+      else
+	throw_(compile_error, "Invalid function definition");
+      break;
+    default:
+      throw_(compile_error, "Invalid function definition");
+    }
+    return wrap_value(value_t());
+  }
+
   ptr_op_t lhs(left()->compile(scope));
   ptr_op_t rhs(kind > UNARY_OPERATORS && has_right() ?
 	       (kind == O_LOOKUP ? right() : right()->compile(scope)) : NULL);
@@ -68,7 +85,7 @@ expr_t::ptr_op_t expr_t::op_t::compile(scope_t& scope)
   ptr_op_t intermediate(copy(lhs, rhs));
 
   // Reduce constants immediately if possible
-  if (lhs->is_value() && (! rhs || rhs->is_value()))
+  if ((! lhs || lhs->is_value()) && (! rhs || rhs->is_value()))
     return wrap_value(intermediate->calc(scope));
 
   return intermediate;
@@ -87,11 +104,17 @@ value_t expr_t::op_t::calc(scope_t& scope, ptr_op_t * context)
     result = as_value();
     break;
 
-  case IDENT:
+  case IDENT: {
     if (! left())
       throw_(calc_error, "Unknown identifier '" << as_ident() << "'");
-    result = left()->calc(scope, context);
+
+    // Evaluating an identifier is the same as calling its definition
+    // directly, so we create an empty call_scope_t to reflect the scope for
+    // this implicit call.
+    call_scope_t call_args(scope);
+    result = left()->calc(call_args, context);
     break;
+  }
 
   case FUNCTION: {
     // Evaluating a FUNCTION is the same as calling it directly; this happens
@@ -102,9 +125,41 @@ value_t expr_t::op_t::calc(scope_t& scope, ptr_op_t * context)
     break;
   }
 
+  case O_DEFINE: {
+    symbol_scope_t local_scope;
+    call_scope_t&  call_args(downcast<call_scope_t>(scope));
+    std::size_t	   args_count = call_args.size();
+    std::size_t	   args_index = 0;
+
+    assert(left()->kind == O_CALL);
+
+    for (ptr_op_t sym = left()->right();
+	 sym;
+	 sym = sym->has_right() ? sym->right() : NULL) {
+      ptr_op_t varname = sym;
+      if (sym->kind == O_COMMA)
+	varname = sym->left();
+
+      if (! varname->is_ident())
+	throw_(calc_error, "Invalid function definition");
+      else if (args_index == args_count)
+	local_scope.define(varname->as_ident(), wrap_value(false));
+      else
+	local_scope.define(varname->as_ident(),
+			   wrap_value(call_args[args_index++]));
+    }
+
+    if (args_index < args_count)
+      throw_(calc_error,
+	     "Too many arguments in function call (saw " << args_count << ")");
+
+    result = right()->compile(local_scope)->calc(local_scope, context);
+    break;
+  }
+
   case O_LOOKUP:
-    if (left()->kind == IDENT &&
-	left()->left() && left()->left()->kind == FUNCTION) {
+    if (left()->is_ident() &&
+	left()->left() && left()->left()->is_function()) {
       call_scope_t call_args(scope);
       if (value_t obj = left()->left()->as_function()(call_args)) {
 	if (obj.is_pointer()) {
@@ -134,18 +189,20 @@ value_t expr_t::op_t::calc(scope_t& scope, ptr_op_t * context)
     const string& name(func->as_ident());
 
     func = func->left();
-    if (! func || func->kind != FUNCTION)
-      throw_(calc_error, "Calling non-function '" << name << "'");
+    if (! func)
+      throw_(calc_error, "Calling unknown function '" << name << "'");
 
-    result = func->as_function()(call_args);
+    if (func->is_function())
+      result = func->as_function()(call_args);
+    else
+      result = func->calc(call_args, context);
     break;
   }
 
   case O_MATCH:
-#if 0
     if (! right()->is_value() || ! right()->as_value().is_mask())
       throw_(calc_error, "Right-hand argument to match operator must be a regex");
-#endif
+
     result = (right()->calc(scope, context).as_mask()
 	      .match(left()->calc(scope, context).to_string()));
     break;
@@ -417,6 +474,14 @@ bool expr_t::op_t::print(std::ostream& out, const context_t& context) const
       found = true;
     break;
 
+  case O_DEFINE:
+    if (left() && left()->print(out, context))
+      found = true;
+    out << " := ";
+    if (has_right() && right()->print(out, context))
+      found = true;
+    break;
+
   case O_LOOKUP:
     if (left() && left()->print(out, context))
       found = true;
@@ -485,6 +550,7 @@ void expr_t::op_t::dump(std::ostream& out, const int depth) const
     out << "FUNCTION";
     break;
 
+  case O_DEFINE: out << "O_DEFINE"; break;
   case O_LOOKUP: out << "O_LOOKUP"; break;
   case O_CALL:	 out << "O_CALL"; break;
   case O_MATCH:	 out << "O_MATCH"; break;
@@ -521,7 +587,7 @@ void expr_t::op_t::dump(std::ostream& out, const int depth) const
 
   // An identifier is a special non-terminal, in that its left() can
   // hold the compiled definition of the identifier.
-  if (kind > TERMINALS || kind == IDENT) {
+  if (kind > TERMINALS || is_ident()) {
     if (left()) {
       left()->dump(out, depth + 1);
       if (kind > UNARY_OPERATORS && has_right())

src/op.h

@@ -110,6 +110,7 @@ public:
 
     O_COMMA,
 
+    O_DEFINE,
     O_LOOKUP,
     O_CALL,
     O_MATCH,

src/parser.cc

@@ -226,6 +226,9 @@ expr_t::parser_t::parse_logic_expr(std::istream& in,
     bool	  negate = false;
 
     switch (tok.kind) {
+    case token_t::DEFINE:
+      kind = op_t::O_DEFINE;
+      break;
     case token_t::EQUAL:
       if (tflags.has_flags(PARSE_NO_ASSIGN))
 	tok.rewind(in);

src/report.cc

@@ -504,6 +504,9 @@ option_t<report_t> * report_t::lookup_option(const char * p)
 
 expr_t::ptr_op_t report_t::lookup(const string& name)
 {
+  if (expr_t::ptr_op_t def = session.lookup(name))
+    return def;
+
   const char * p = name.c_str();
   switch (*p) {
   case 'a':
@@ -639,7 +642,7 @@ expr_t::ptr_op_t report_t::lookup(const string& name)
   if (option_t<report_t> * handler = lookup_option(p))
     return MAKE_OPT_FUNCTOR(report_t, handler);
 
-  return session.lookup(name);
+  return NULL;
 }
 
 } // namespace ledger

src/report.h

@@ -166,6 +166,10 @@ public:
 
   option_t<report_t> * lookup_option(const char * p);
 
+  virtual void define(const string& name, expr_t::ptr_op_t def) {
+    session.define(name, def);
+  }
+
   virtual expr_t::ptr_op_t lookup(const string& name);
 
   /**

src/scope.cc

@@ -35,7 +35,7 @@ namespace ledger {
 
 void symbol_scope_t::define(const string& name, expr_t::ptr_op_t def)
 {
-  DEBUG("ledger.xpath.syms", "Defining '" << name << "' = " << def);
+  DEBUG("scope.symbols", "Defining '" << name << "' = " << def);
 
   std::pair<symbol_map::iterator, bool> result
     = symbols.insert(symbol_map::value_type(name, def));
@@ -47,8 +47,7 @@ void symbol_scope_t::define(const string& name, expr_t::ptr_op_t def)
     std::pair<symbol_map::iterator, bool> result2
       = symbols.insert(symbol_map::value_type(name, def));
     if (! result2.second)
-      throw_(compile_error,
-	     "Redefinition of '" << name << "' in same scope");
+      throw_(compile_error, "Redefinition of '" << name << "' in same scope");
   }
 }
 

src/scope.h

@@ -66,6 +66,7 @@ public:
     TRACE_DTOR(scope_t);
   }
 
+  virtual void define(const string& name, expr_t::ptr_op_t def) {}
   virtual expr_t::ptr_op_t lookup(const string& name) = 0;
 
   value_t resolve(const string& name) {
@@ -98,6 +99,11 @@ public:
     TRACE_DTOR(child_scope_t);
   }
 
+  virtual void define(const string& name, expr_t::ptr_op_t def) {
+    if (parent)
+      parent->define(name, def);
+  }
+
   virtual expr_t::ptr_op_t lookup(const string& name) {
     if (parent)
       return parent->lookup(name);
@@ -127,12 +133,6 @@ public:
     TRACE_DTOR(symbol_scope_t);
   }
 
-  void define(const string& name, const value_t& val) {
-    define(name, expr_t::op_t::wrap_value(val));
-  }
-  void define(const string& name, const function_t& func) {
-    define(name, expr_t::op_t::wrap_functor(func));
-  }
   virtual void define(const string& name, expr_t::ptr_op_t def);
 
   virtual expr_t::ptr_op_t lookup(const string& name);
@@ -211,6 +211,11 @@ public:
     TRACE_DTOR(bind_scope_t);
   }
 
+  virtual void define(const string& name, expr_t::ptr_op_t def) {
+    parent->define(name, def);
+    grandchild.define(name, def);
+  }
+
   virtual expr_t::ptr_op_t lookup(const string& name) {
     if (expr_t::ptr_op_t def = grandchild.lookup(name))
       return def;

src/session.cc

@@ -206,7 +206,8 @@ expr_t::ptr_op_t session_t::lookup(const string& name)
     }
     break;
   }
-  return NULL;
+
+  return symbol_scope_t::lookup(name);
 }
 
 } // namespace ledger

src/session.h

@@ -58,7 +58,7 @@ namespace ledger {
  *
  * Long.
  */
-class session_t : public noncopyable, public scope_t
+class session_t : public symbol_scope_t
 {
   friend void set_session_context(session_t * session);
 

src/token.cc

@@ -258,6 +258,15 @@ void expr_t::token_t::next(std::istream& in, const uint_least8_t pflags)
     break;
   case ':':
     in.get(c);
+    c = in.peek();
+    if (c == '=') {
+      in.get(c);
+      symbol[1] = c;
+      symbol[2] = '\0';
+      kind = DEFINE;
+      length = 2;
+      break;
+    }
     kind = COLON;
     break;
 

src/token.h

@@ -73,6 +73,7 @@ struct expr_t::token_t : public noncopyable
     GREATER,			// >
     GREATEREQ,			// >=
 
+    DEFINE,			// :=
     ASSIGN,			// =
     MATCH,			// =~
     NMATCH,			// !~

src/value.cc

@@ -1715,7 +1715,7 @@ void value_t::dump(std::ostream& out, const bool relaxed) const
 {
   switch (type()) {
   case VOID:
-    out << "";
+    out << "<null>";
     break;
 
   case BOOLEAN: