Update some examples.

resources/examples/binarydigits.c3

@@ -15,6 +15,7 @@ fn DString bin(int x)
 {
     int bits = x == 0 ? 1 : 1 + (int)math::log2(x);
     DString str;
+    str.new_init();
     str.append_repeat('0', bits);
     for (int i = 0; i < bits; i++)
     {

resources/examples/binarydigits7.c3

@@ -0,0 +1,24 @@
+module binarydigits;
+import std::math;
+import std::io;
+fn void main()
+{
+    for (int i = 0; i < 20; i++)
+    {
+        DString s = bin(i);
+        io::printf("%s\n", s);
+    }
+}
+
+fn DString bin(int x)
+{
+    int bits = x == 0 ? 1 : 1 + (int)math::log2(x);
+    DString str;
+    str.append_repeat('0', bits);
+    for (int i = 0; i < bits; i++)
+    {
+        str.set((usz)(bits - i - 1), x & 1 ? '1' : '0');
+        x >>= 1;
+    }
+    return str;
+}

resources/examples/contextfree/boolerr7.c3

@@ -0,0 +1,101 @@
+
+module test;
+import libc;
+import std::io;
+import std::collections::maybe;
+
+fault TitleResult
+{
+	TITLE_MISSING
+}
+
+fault ReadError
+{
+	BAD_READ,
+}
+
+struct Doc
+{
+	Maybe { Head } head;
+}
+
+struct Head
+{
+	Maybe { String } title;
+}
+
+struct Summary
+{
+	Maybe { String } title;
+	bool ok;
+}
+
+fn void! Summary.print(Summary* s, OutStream out)
+{
+	io::fprintf(out, "Summary({ .title = %s, .ok = %s})", s.title.get() ?? "missing", s.ok)!;
+}
+
+fn Doc! read_doc(String url)
+{
+	if (url.contains("fail")) return ReadError.BAD_READ?;
+	if (url.contains("head-missing")) return { };
+	if (url.contains("title-missing")) return { .head = maybe::value{Head}({}) };
+	if (url.contains("title-empty")) return { .head = maybe::value{Head}({ .title = maybe::value{String}("")}) };
+	return { .head = maybe::value{Head}({ .title = maybe::value{String}(string::format(mem, "Title of %s", url)) }) };
+}
+
+fn Summary build_summary(Doc doc)
+{
+    return {
+        .title = maybe::value{String}(doc.head.get().title.get()) ?? {},
+        .ok = true,
+    };
+}
+
+fn Summary read_and_build_summary(String url)
+{
+	return build_summary(read_doc(url)) ?? {};
+}
+
+fn bool! is_title_non_empty(Doc doc)
+{
+	String! title = doc.head.get().title.get();
+	if (catch title) return TitleResult.TITLE_MISSING?;
+	return title.len > 0;
+}
+
+fn bool! read_whether_title_non_empty(String url)
+{
+    return is_title_non_empty(read_doc(url));
+}
+
+fn String bool_to_string(bool b)
+{
+	return b ? "true" : "false";
+}
+
+fn void main()
+{
+    const String[] URLS = { "good", "title-empty", "title-missing", "head-missing", "fail" };
+    DynamicArenaAllocator dynamic_arena;
+	dynamic_arena.init(1024, allocator::heap());
+	OutStream out = io::stdout();
+    foreach (String url : URLS)
+    {
+        mem::@scoped(&dynamic_arena)
+        {
+            io::printf(`Checking "https://%s/":` "\n", url);
+            Summary summary = read_and_build_summary(url);
+            io::fprintf(out, "  Summary: ")!!;
+            summary.print(out)!!;
+            io::fprintn(out, "")!!;
+            io::fprintf(out, "  Title: %s\n", summary.title.get() ?? "")!!;
+            bool! has_title = read_whether_title_non_empty(url);
+            // This looks a bit less than elegant, but as you see it's mostly due to having to
+            // use printf here.
+            io::fprintf(out, "  Has title: %s vs %s\n", bool_to_string(has_title) ?? (@catch(has_title)).nameof, has_title ?? false)!!;
+        };
+        dynamic_arena.reset();
+    }
+    dynamic_arena.free();
+}