xo-reader: exprreplxx example program, now with line editing

xo-reader/examples/exprreplxx/exprreplxx.cpp

@@ -0,0 +1,108 @@
+/** @file exprreplxx.cpp **/
+
+#include "xo/reader/reader.hpp"
+#include <replxx.hxx>
+#include <iostream>
+#include <unistd.h> // for isatty
+
+// presumeably replxx assumes input is a tty
+//
+bool replxx_getline(bool interactive, std::size_t parser_stack_size, replxx::Replxx & rx, std::string& input)
+{
+    using namespace std;
+
+    char const * prompt = "";
+
+    if (interactive) {
+        if (parser_stack_size <= 1)
+            prompt = "> ";
+        else
+            prompt = ". ";
+    }
+
+    const char * input_cstr = rx.input(prompt);
+
+    bool retval = (input_cstr != nullptr);
+
+    if (retval) {
+        //cerr << "got reval->true" << endl;
+
+        input = input_cstr;
+
+    } else {
+        //cerr << "got retval->false" << endl;
+    }
+
+    rx.history_add(input);
+
+    return retval;
+}
+
+void
+welcome(std::ostream& os)
+{
+    using namespace std;
+
+    os << "read-eval-print loop for schematika expressions" << endl;
+    os << "  ctrl-a/ctrl-e   beginning/end of line" << endl;
+    os << "  ctrl-u          delete entire line" << endl;
+    os << "  ctrl-k          delete to end of line" << endl;
+    os << "  meta-<bs>       backward delete word" << endl;
+    os << "  <up>|meta-p     previous command from history" << endl;
+    os << "  <down>|meta-n   next command from history" << endl;
+    os << "  <pgup>/<pgdown> page through history faster" << endl;
+    os << "  ctrl-s/ctrl-r   forward/backward history search" << endl;
+    os << endl;
+}
+
+int
+main() {
+    using namespace replxx;
+    using namespace xo::scm;
+    using namespace std;
+
+    using span_type = xo::scm::span<const char>;
+
+    bool interactive = isatty(STDIN_FILENO);
+
+    Replxx rx;
+    rx.set_max_history_size(1000);
+    rx.history_load("repl_history.txt");
+//    rx.bind_key_internal(Replxx::KEY::control('p'), "history_previous");
+//    rx.bind_key_internal(Replxx::KEY::control('n'), "history_next");
+
+    reader rdr;
+    rdr.begin_interactive_session();
+
+    string input_str;
+
+    bool eof = false;
+
+    span_type input;
+    std::size_t parser_stack_size = 0;
+
+    welcome(cerr);
+
+    while (replxx_getline(interactive, parser_stack_size, rx, input_str)) {
+        input  = span_type::from_string(input_str);
+
+        while (!input.empty()) {
+            auto [expr, consumed, psz] = rdr.read_expr(input, eof);
+
+            if (expr) {
+                cout << expr << endl;
+            }
+
+            input = input.after_prefix(consumed);
+            parser_stack_size = psz;
+        }
+    }
+
+    auto [expr, _1, _2] = rdr.read_expr(input, true /*eof*/);
+
+    if (expr) {
+        cout << expr << endl;
+    }
+
+    rx.history_save("repl_history.txt");
+}