xo-reader: + exprrepl example

README.md

@@ -28,7 +28,7 @@ $ cmake -B .build0 -S xo-cmake -DCMAKE_INSTALL_PREFIX=${PREFIX}
 $ cmake --build .build0
 $ cmake --install .build0
 # phase 2
-$ cmake -B .build -S . -DCMAKE_INSTALL_PREFIX=${PREFIX}
+$ cmake -B .build -S . -DCMAKE_INSTALL_PREFIX=${PREFIX} -DXO_ENABLE_EXAMPLES=1
 $ cmake --build .build
 $ cmake --install .build
 ```

xo-reader/examples/CMakeLists.txt

@@ -0,0 +1 @@
+add_subdirectory(exprrepl)

xo-reader/examples/exprrepl/CMakeLists.txt

@@ -0,0 +1,11 @@
+# xo-reader/example/exprrepl/CMakeLists.txt
+
+set(SELF_EXE xo_expression_repl)
+set(SELF_SRCS exprrepl.cpp)
+
+if (XO_ENABLE_EXAMPLES)
+    xo_add_executable(${SELF_EXE} ${SELF_SRCS})
+    xo_dependency(${SELF_EXE} xo_reader)
+endif()
+
+# end CMakeLists.txt

xo-reader/examples/exprrepl/exprrepl.cpp

@@ -0,0 +1,61 @@
+/** @file exprrepl.cpp **/
+
+#include "xo/reader/reader.hpp"
+#include <iostream>
+#include <unistd.h> // for isatty
+
+bool repl_getline(bool interactive, std::istream& in, std::ostream& out, std::string& input)
+{
+    if (interactive) {
+        out << "> ";
+        std::flush(out);
+    }
+
+    bool retval = static_cast<bool>(std::getline(in, input));
+
+    if (retval) {
+        // want reader to see newline, it's syntax
+        input.push_back('\n');
+    }
+
+    return retval;
+}
+
+int
+main() {
+    using namespace xo::scm;
+    using namespace std;
+
+    using span_type = xo::scm::span<const char>;
+
+    bool interactive = isatty(STDIN_FILENO);
+
+    reader rdr;
+    rdr.begin_interactive_session();
+
+    string input_str;
+
+    bool eof = false;
+
+    span_type input;
+
+    while (repl_getline(interactive, cin, cout, input_str)) {
+        input  = span_type::from_string(input_str);
+
+        while (!input.empty()) {
+            auto [expr, consumed] = rdr.read_expr(input, eof);
+
+            if (expr) {
+                cout << expr << endl;
+            }
+
+            input = input.after_prefix(consumed);
+        }
+    }
+
+    auto [expr, _] = rdr.read_expr(input, true /*eof*/);
+
+    if (expr) {
+        cout << expr << endl;
+    }
+}