438 lines
16 KiB
C++
438 lines
16 KiB
C++
//: The goal of layers is to make programs more easy to understand and more
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//: malleable, easy to rewrite in radical ways without accidentally breaking
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//: some corner case. Tests further both goals. They help understandability by
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//: letting one make small changes and get feedback. What if I wrote this line
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//: like so? What if I removed this function call, is it really necessary?
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//: Just try it, see if the tests pass. Want to explore rewriting this bit in
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//: this way? Tests put many refactorings on a firmer footing.
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//:
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//: But the usual way we write tests seems incomplete. Refactorings tend to
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//: work in the small, but don't help with changes to function boundaries. If
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//: you want to extract a new function you have to manually test-drive it to
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//: create tests for it. If you want to inline a function its tests are no
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//: longer valid. In both cases you end up having to reorganize code as well as
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//: tests, an error-prone activity.
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//:
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//: In response, this layer introduces the notion of *domain-driven* testing.
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//: We focus on the domain of inputs the whole program needs to handle rather
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//: than the correctness of individual functions. All tests invoke the program
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//: in a single way: by calling run() with some input. As the program operates
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//: on the input, it traces out a list of _facts_ deduced about the domain:
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//: trace("label") << "fact 1: " << val;
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//:
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//: Tests can now check these facts:
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//: :(scenario foo)
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//: 34 # call run() with this input
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//: +label: fact 1: 34 # 'run' should have deduced this fact
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//: -label: fact 1: 35 # the trace should not contain such a fact
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//:
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//: Since we never call anything but the run() function directly, we never have
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//: to rewrite the tests when we reorganize the internals of the program. We
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//: just have to make sure our rewrite deduces the same facts about the domain,
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//: and that's something we're going to have to do anyway.
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//:
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//: To avoid the combinatorial explosion of integration tests, each layer
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//: mainly logs facts to the trace with a common *label*. All tests in a layer
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//: tend to check facts with this label. Validating the facts logged with a
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//: specific label is like calling functions of that layer directly.
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//:
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//: To build robust tests, trace facts about your domain rather than details of
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//: how you computed them.
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//:
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//: More details: http://akkartik.name/blog/tracing-tests
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//:
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//: ---
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//:
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//: Between layers and domain-driven testing, programming starts to look like a
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//: fundamentally different activity. Instead of a) superficial, b) local rules
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//: on c) code [like say http://blog.bbv.ch/2013/06/05/clean-code-cheat-sheet],
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//: we allow programmers to engage with the a) deep, b) global structure of the
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//: c) domain. If you can systematically track discontinuities in the domain,
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//: you don't care if the code used gotos as long as it passed the tests. If
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//: tests become more robust to run it becomes easier to try out radically
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//: different implementations for the same program. If code is super-easy to
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//: rewrite, it becomes less important what indentation style it uses, or that
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//: the objects are appropriately encapsulated, or that the functions are
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//: referentially transparent.
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//:
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//: Instead of plumbing, programming becomes building and gradually refining a
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//: map of the environment the program must operate under. Whether a program is
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//: 'correct' at a given point in time is a red herring; what matters is
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//: avoiding regression by monotonically nailing down the more 'eventful' parts
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//: of the terrain. It helps readers new and old, and rewards curiosity, to
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//: organize large programs in self-similar hierarchies of example scenarios
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//: colocated with the code that makes them work.
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//:
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//: "Programming properly should be regarded as an activity by which
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//: programmers form a mental model, rather than as production of a program."
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//: -- Peter Naur (http://alistair.cockburn.us/ASD+book+extract%3A+%22Naur,+Ehn,+Musashi%22)
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:(before "End Types")
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struct trace_line {
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int depth; // optional field just to help browse traces later
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string label;
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string contents;
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trace_line(string l, string c) :depth(0), label(l), contents(c) {}
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trace_line(int d, string l, string c) :depth(d), label(l), contents(c) {}
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};
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//: Support for tracing an entire run.
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//: Traces can have a lot of overhead, so only turn them on when asked.
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:(before "End Commandline Options(*arg)")
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else if (is_equal(*arg, "--trace")) {
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Save_trace = true;
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}
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:(before "End Commandline Parsing")
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if (Save_trace) {
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cerr << "initializing trace\n";
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Trace_stream = new trace_stream;
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}
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:(code)
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void cleanup_main() {
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if (!Trace_stream) return;
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if (Save_trace)
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Trace_stream->save();
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delete Trace_stream;
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Trace_stream = NULL;
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}
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:(before "End One-time Setup")
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atexit(cleanup_main);
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:(before "End Types")
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// Pre-define some global constants that trace_stream needs to know about.
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// Since they're in the Types section, they'll be included in any cleaved
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// compilation units. So no extern linkage.
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const int Max_depth = 9999;
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const int Error_depth = 0; // definitely always print errors
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const int App_depth = 2; // temporarily where all Mu code will trace to
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struct trace_stream {
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vector<trace_line> past_lines;
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// accumulator for current line
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ostringstream* curr_stream;
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string curr_label;
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int curr_depth;
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int callstack_depth;
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int collect_depth;
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ofstream null_stream; // never opens a file, so writes silently fail
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trace_stream() :curr_stream(NULL), curr_depth(Max_depth), callstack_depth(0), collect_depth(Max_depth) {}
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~trace_stream() { if (curr_stream) delete curr_stream; }
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ostream& stream(string label) {
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return stream(Max_depth, label);
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}
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ostream& stream(int depth, string label) {
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if (depth > collect_depth) return null_stream;
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curr_stream = new ostringstream;
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curr_label = label;
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curr_depth = depth;
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return *curr_stream;
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}
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void save() {
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cerr << "saving trace to 'last_run'\n";
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ofstream fout("last_run");
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fout << readable_contents("");
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fout.close();
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}
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// be sure to call this before messing with curr_stream or curr_label
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void newline();
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// useful for debugging
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string readable_contents(string label); // empty label = show everything
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};
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:(code)
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void trace_stream::newline() {
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if (!curr_stream) return;
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string curr_contents = curr_stream->str();
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if (!curr_contents.empty()) {
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past_lines.push_back(trace_line(curr_depth, trim(curr_label), curr_contents)); // preserve indent in contents
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if ((!Hide_errors && curr_label == "error")
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|| Dump_trace
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|| (!Dump_label.empty() && curr_label == Dump_label))
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cerr << curr_label << ": " << curr_contents << '\n';
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}
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delete curr_stream;
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curr_stream = NULL;
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curr_label.clear();
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curr_depth = Max_depth;
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}
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string trace_stream::readable_contents(string label) {
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ostringstream output;
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label = trim(label);
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for (vector<trace_line>::iterator p = past_lines.begin(); p != past_lines.end(); ++p)
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if (label.empty() || label == p->label)
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output << std::setw(4) << p->depth << ' ' << p->label << ": " << p->contents << '\n';
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return output.str();
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}
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:(before "End Globals")
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trace_stream* Trace_stream = NULL;
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int Trace_errors = 0; // used only when Trace_stream is NULL
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:(before "End Globals")
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bool Hide_errors = false; // if set, don't print even error trace lines to screen
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bool Dump_trace = false; // if set, print trace lines to screen
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string Dump_label = ""; // if set, print trace lines matching a single label to screen
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:(before "End Reset")
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Hide_errors = false;
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Dump_trace = false; // toggle this to print traces to screen as they are emitted
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Dump_label = "";
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:(before "End Includes")
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#define CLEAR_TRACE delete Trace_stream, Trace_stream = new trace_stream;
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// Top-level helper. IMPORTANT: can't nest
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#define trace(...) !Trace_stream ? cerr /*print nothing*/ : Trace_stream->stream(__VA_ARGS__)
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// Just for debugging; 'git log' should never show any calls to 'dbg'.
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#define dbg trace(0, "a")
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#define DUMP(label) if (Trace_stream) cerr << Trace_stream->readable_contents(label);
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// Errors are a special layer.
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#define raise (!Trace_stream ? (scroll_to_bottom_and_close_console(),++Trace_errors,cerr) /*do print*/ : Trace_stream->stream(Error_depth, "error"))
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// If we aren't yet sure how to deal with some corner case, use assert_for_now
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// to indicate that it isn't an inviolable invariant.
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#define assert_for_now assert
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//: Automatically close the console in some situations.
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:(before "End One-time Setup")
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atexit(scroll_to_bottom_and_close_console);
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:(code)
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void scroll_to_bottom_and_close_console() {
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if (!tb_is_active()) return;
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// leave the screen in a relatively clean state
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tb_set_cursor(tb_width()-1, tb_height()-1);
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cout << "\r\n";
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tb_shutdown();
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}
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// Inside tests, fail any tests that displayed (unexpected) errors.
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// Expected errors in tests should always be hidden and silently checked for.
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:(before "End Test Teardown")
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if (Passed && !Hide_errors && trace_contains_errors()) {
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Passed = false;
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}
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:(code)
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bool trace_contains_errors() {
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return Trace_errors > 0 || trace_count("error") > 0;
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}
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:(before "End Types")
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struct end {};
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:(code)
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ostream& operator<<(ostream& os, end /*unused*/) {
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if (Trace_stream) Trace_stream->newline();
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return os;
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}
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:(before "End Globals")
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bool Save_trace = false; // if set, write out trace to disk
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// Trace_stream is a resource, lease_tracer uses RAII to manage it.
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:(before "End Types")
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struct lease_tracer {
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lease_tracer();
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~lease_tracer();
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};
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:(code)
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lease_tracer::lease_tracer() { Trace_stream = new trace_stream; }
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lease_tracer::~lease_tracer() {
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if (Save_trace) Trace_stream->save();
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delete Trace_stream, Trace_stream = NULL;
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}
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:(before "End Includes")
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#define START_TRACING_UNTIL_END_OF_SCOPE lease_tracer leased_tracer;
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:(before "End Test Setup")
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START_TRACING_UNTIL_END_OF_SCOPE
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:(before "End Includes")
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#define CHECK_TRACE_CONTENTS(...) check_trace_contents(__FUNCTION__, __FILE__, __LINE__, __VA_ARGS__)
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#define CHECK_TRACE_CONTAINS_ERRORS() CHECK(trace_contains_errors())
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#define CHECK_TRACE_DOESNT_CONTAIN_ERRORS() \
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if (Passed && trace_contains_errors()) { \
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cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): unexpected errors\n"; \
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DUMP("error"); \
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Passed = false; \
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return; \
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}
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#define CHECK_TRACE_COUNT(label, count) \
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if (Passed && trace_count(label) != (count)) { \
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cerr << "\nF - " << __FUNCTION__ << "(" << __FILE__ << ":" << __LINE__ << "): trace_count of " << label << " should be " << count << '\n'; \
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cerr << " got " << trace_count(label) << '\n'; /* multiple eval */ \
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DUMP(label); \
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Passed = false; \
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return; /* Currently we stop at the very first failure. */ \
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}
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#define CHECK_TRACE_DOESNT_CONTAIN(...) CHECK(trace_doesnt_contain(__VA_ARGS__))
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:(code)
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bool check_trace_contents(string FUNCTION, string FILE, int LINE, string expected) {
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if (!Passed) return false;
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if (!Trace_stream) return false;
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vector<string> expected_lines = split(expected, "");
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int curr_expected_line = 0;
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while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
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++curr_expected_line;
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if (curr_expected_line == SIZE(expected_lines)) return true;
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string label, contents;
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split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
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for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin(); p != Trace_stream->past_lines.end(); ++p) {
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if (label != p->label) continue;
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if (contents != trim(p->contents)) continue;
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++curr_expected_line;
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while (curr_expected_line < SIZE(expected_lines) && expected_lines.at(curr_expected_line).empty())
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++curr_expected_line;
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if (curr_expected_line == SIZE(expected_lines)) return true;
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split_label_contents(expected_lines.at(curr_expected_line), &label, &contents);
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}
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if (line_exists_anywhere(label, contents)) {
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cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): line [" << label << ": " << contents << "] out of order in trace:\n";
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DUMP("");
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}
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else {
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cerr << "\nF - " << FUNCTION << "(" << FILE << ":" << LINE << "): missing [" << contents << "] in trace:\n";
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DUMP(label);
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}
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Passed = false;
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return false;
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}
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void split_label_contents(const string& s, string* label, string* contents) {
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static const string delim(": ");
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size_t pos = s.find(delim);
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if (pos == string::npos) {
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*label = "";
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*contents = trim(s);
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}
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else {
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*label = trim(s.substr(0, pos));
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*contents = trim(s.substr(pos+SIZE(delim)));
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}
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}
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bool line_exists_anywhere(const string& label, const string& contents) {
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for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin(); p != Trace_stream->past_lines.end(); ++p) {
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if (label != p->label) continue;
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if (contents == trim(p->contents)) return true;
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}
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return false;
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}
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int trace_count(string label) {
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return trace_count(label, "");
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}
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int trace_count(string label, string line) {
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if (!Trace_stream) return 0;
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long result = 0;
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for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin(); p != Trace_stream->past_lines.end(); ++p) {
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if (label == p->label) {
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if (line == "" || trim(line) == trim(p->contents))
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++result;
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}
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}
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return result;
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}
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int trace_count_prefix(string label, string prefix) {
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if (!Trace_stream) return 0;
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long result = 0;
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for (vector<trace_line>::iterator p = Trace_stream->past_lines.begin(); p != Trace_stream->past_lines.end(); ++p) {
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if (label == p->label) {
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if (starts_with(trim(p->contents), trim(prefix)))
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++result;
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}
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}
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return result;
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}
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bool trace_doesnt_contain(string label, string line) {
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return trace_count(label, line) == 0;
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}
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bool trace_doesnt_contain(string expected) {
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vector<string> tmp = split_first(expected, ": ");
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if (SIZE(tmp) == 1) {
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raise << expected << ": missing label or contents in trace line\n" << end();
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assert(false);
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}
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return trace_doesnt_contain(tmp.at(0), tmp.at(1));
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}
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vector<string> split(string s, string delim) {
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vector<string> result;
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size_t begin=0, end=s.find(delim);
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while (true) {
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if (end == string::npos) {
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result.push_back(string(s, begin, string::npos));
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break;
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}
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result.push_back(string(s, begin, end-begin));
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begin = end+SIZE(delim);
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end = s.find(delim, begin);
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}
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return result;
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}
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vector<string> split_first(string s, string delim) {
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vector<string> result;
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size_t end=s.find(delim);
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result.push_back(string(s, 0, end));
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if (end != string::npos)
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result.push_back(string(s, end+SIZE(delim), string::npos));
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return result;
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}
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string trim(const string& s) {
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string::const_iterator first = s.begin();
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while (first != s.end() && isspace(*first))
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++first;
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if (first == s.end()) return "";
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string::const_iterator last = --s.end();
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while (last != s.begin() && isspace(*last))
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--last;
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++last;
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return string(first, last);
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}
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:(before "End Includes")
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#include <vector>
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using std::vector;
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#include <list>
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using std::list;
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#include <set>
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using std::set;
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#include <sstream>
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using std::istringstream;
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using std::ostringstream;
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#include <fstream>
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using std::ifstream;
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using std::ofstream;
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#include "termbox/termbox.h"
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:(before "End Globals")
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//: In future layers we'll use the depth field as follows:
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//:
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//: Errors will be depth 0.
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//: Mu 'applications' will be able to use depths 1-100 as they like.
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//: Primitive statements will occupy 101-9989
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extern const int Initial_callstack_depth = 101;
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extern const int Max_callstack_depth = 9989;
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//: Finally, details of primitive Mu statements will occupy depth 9990-9999
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//: (more on that later as well)
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//:
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//: This framework should help us hide some details at each level, mixing
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//: static ideas like layers with the dynamic notion of call-stack depth.
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