Add functional visitor to exprt

Includes unit test.

Author: Petr Bauch

src/util/expr.cpp

@@ -279,6 +279,20 @@ void exprt::visit(const_expr_visitort &visitor) const
   }
 }
 
+void exprt::visit(const std::function<void(const exprt &)> &f) const
+{
+  std::stack<const exprt *> stack;
+  stack.push(this);
+  while(!stack.empty())
+  {
+    const exprt &expr = *stack.top();
+    stack.pop();
+    f(expr);
+    forall_operands(it, expr)
+      stack.push(&(*it));
+  }
+}
+
 depth_iteratort exprt::depth_begin()
 { return depth_iteratort(*this); }
 depth_iteratort exprt::depth_end()

src/util/expr.h

@@ -305,6 +305,12 @@ class exprt:public irept
   void visit(class expr_visitort &visitor);
   void visit(class const_expr_visitort &visitor) const;
 
+  /// Recursively traverse the expression tree (via operands) and call \p f on
+  /// every subexpressions, including `this`. The input function has
+  /// side-effects and does not modify the expression.
+  /// \param f: The function to be call on subexpressions
+  void visit(const std::function<void(const exprt &)> &f) const;
+
   depth_iteratort depth_begin();
   depth_iteratort depth_end();
   const_depth_iteratort depth_begin() const;

unit/Makefile

@@ -56,6 +56,7 @@ SRC += analyses/ai/ai.cpp \
        util/string_utils/strip_string.cpp \
        util/symbol_table.cpp \
        util/unicode.cpp \
+       util/visit.cpp \
        # Empty last line
 
 INCLUDES= -I ../src/ -I.

unit/util/visit.cpp

@@ -0,0 +1,42 @@
+/*******************************************************************\
+
+Module: Unit test for expr.h/visit
+
+Author: Diffblue Ltd
+
+\*******************************************************************/
+
+#include <testing-utils/catch.hpp>
+
+#include <util/arith_tools.h>
+#include <util/expr.h>
+#include <util/std_expr.h>
+#include <util/std_types.h>
+
+SCENARIO("visiting reaches all subnodes", "[core][util][expr]")
+{
+  GIVEN("An exprt representing a binary relation")
+  {
+    const typet type1 = signedbv_typet(32);
+    irep_idt symbol_name = "a";
+    symbol_exprt varx(symbol_name, type1);
+    exprt val10 = from_integer(10, type1);
+    binary_relation_exprt x_le_10(varx, ID_le, val10);
+
+    THEN("counting nodes should return 3")
+    {
+      size_t count = 0;
+      x_le_10.visit([&](const exprt &) { count++; });
+      REQUIRE(count == 3);
+    }
+    THEN("counting symbol should return 1")
+    {
+      size_t count = 0;
+      x_le_10.visit([&](const exprt &e) {
+        if(e.id() == ID_symbol)
+          count++;
+      });
+      REQUIRE(count == 1);
+    }
+  }
+}