Add verbosity stream

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/util/CMakeLists.txt

@@ -1 +1 @@
-add_library(util trace.cpp debug.cpp name.cpp exception.cpp)
+add_library(util trace.cpp debug.cpp name.cpp exception.cpp verbosity.cpp)

src/util/verbosity.cpp

@@ -0,0 +1,31 @@
+/*
+Copyright (c) 2013 Microsoft Corporation. All rights reserved. 
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura 
+*/
+#include "verbosity.h"
+
+namespace lean {
+
+unsigned g_verbosity_level = 0;
+
+void set_verbosity_level(unsigned lvl) {
+    g_verbosity_level = lvl;
+}
+
+unsigned get_verbosity_level() {
+    return g_verbosity_level;
+}
+
+static std::ostream* g_verbose_stream = &std::cerr;
+
+void set_verbose_stream(std::ostream& str) {
+    g_verbose_stream = &str;
+}
+
+std::ostream& verbose_stream() {
+    return *g_verbose_stream;
+}
+
+}

src/util/verbosity.h

@@ -0,0 +1,18 @@
+/*
+Copyright (c) 2013 Microsoft Corporation. All rights reserved. 
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura 
+*/
+#pragma once
+#include <iostream>
+
+namespace lean {
+void          set_verbosity_level(unsigned lvl);
+unsigned      get_verbosity_level();
+std::ostream& verbose_stream();
+void          set_verbose_stream(std::ostream& s);
+#define lean_verbose(LVL, CODE) { if (get_verbosity_level() >= LVL) { CODE } }
+}
+
+