Write main application code

app/main.c

@@ -1,7 +1,25 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+#include "evaluator.h"
+#include "reader.h"
+#include "repl.h"
+
+static void print(const char *output, int len)
+{
+	fwrite(output, 1, len, stdout);
+}
+
+static repl_t repl = {
+	.get_byte = getchar,
+	.read = read_expression,
+	.evaluate = evaluate,
+	.print = print,
+};
+
 int main(void)
 {
+	init_repl(&repl);
+	run_repl(&repl);
 	return EXIT_SUCCESS;
 }