adding a new command to the REPL

src/main.zig

@@ -1,18 +1,32 @@
 const std = @import("std");
+const mem = @import("memory.zig");
 
 pub fn main() !void {
+    var memory = mem.Memory.init();
     var input = std.io.getStdIn().reader();
     std.debug.print("MI-HA-RU (386) REPL\nType 'exit' to quit.\n", .{});
     var buffer: [256]u8 = undefined;
     while (true) {
         std.debug.print("> ", .{});
         const line = try input.readUntilDelimiterOrEof(&buffer, '\n');
-        if (line == null) {
+        const clean = std.mem.trim(u8, line.?, " \n\r");
+        var it = std.mem.splitSequence(u8, clean, " ");
+        if (it.next()) |first_argument| {
+            if (std.mem.eql(u8, first_argument, "exit")) {
                 break;
+            } else if (std.mem.eql(u8, first_argument, "mem")) {
+                try handleMemoryCommand(&memory, &it);
             }
-
-        if (std.mem.eql(u8, line.?, "exit")) {
-            break;
+        } else {
+            // noop
         }
     }
 }
+
+fn handleMemoryCommand(memory: *mem.Memory, it: anytype) !void {
+    if (it.next()) |next_argument| {
+        const addr = try std.fmt.parseUnsigned(u8, next_argument, 10);
+        const value = try memory.readByte(addr);
+        std.debug.print("{}\n", .{value});
+    }
+}

src/memory.zig

@@ -0,0 +1,15 @@
+const MEM_SIZE: usize = 1 * 1024 * 1024; // 1mb
+
+pub const Memory = struct {
+    data: [MEM_SIZE]u8,
+
+    pub fn init() Memory {
+        return Memory{
+            .data = [_]u8{0} ** MEM_SIZE,
+        };
+    }
+
+    pub fn readByte(self: *Memory, addr: u8) !u8 {
+        return self.data[addr];
+    }
+};