abacus: parse standard output and output result

src/abacus.cc

@@ -1,5 +1,9 @@
-#include <iostream>
+#include "parser-driver.hh" // FIXME: I would like `parse/parser-driver.hh` path instead...
 
 int main() {
-    std::cout << "Hello World!\n";
+    abacus::parse::ParserDriver driver{};
+
+    driver.parse("-");
+
+    std::cout << driver.result();
 }

src/meson.build

@@ -8,4 +8,8 @@ subdir('parse')
 abacus = executable(
   'abacus',
   sources: abacus_sources,
+  dependencies: [
+    bignum,
+    parse,
+  ],
 )