Iridium

This may shock you, but they are a bit more complicated than they might seem. Since a computer cares about bytes, it has no concept of the letter s, ! or any other letter. These having meaning to us humans. But we want our users to be able to give input and read output without having to do it all in hex. The solution is to use some sort of character encoding. This maps a particular character to a number. You’ll hear two common encodings mentioned these days: ASCII and UTF. I’m not going to go into an exhaustive history of them; for that, check out this article for ASCII and this article for UTF-8. I will cover enough for us to put in support for strings, though.

Our assembler right now can recognize one opcode, load. We need to teach it to recognize all the rest. There’s a couple ways we can do that:

Let’s go with option #2, since it will require much less copy-paste. It also gives us an excuse to implement From<CompleteStr<_>> for our opcodes! == The From<&str> Trait In instruction.rs, below the block where we implemented From<u8>, put this:

You know how I’ve written several times we’ll come back and fix/change stuff later?

We could torture ourselves by writing all our programs in hex, and if that’s your thing, this section is technically optional.

REPL stands for Read, Evaluate, and Print Loop. It is also referred to as the interactive interpreter for a language. For example, if you open up Terminal or iTerm, we can look at Python’s REPL:

Our current REPL doesn’t do a ton, so let’s fix that. In this post, we’ll be adding some commands to look at the program bytecode and the registers and their contents, as well as actually execute code entered in as hexadecimal.