From: Mark Sparshatt <msparshatt@...>
Date: 2004-04-03T21:49:15+09:00
Subject: Re: Learning Ruby, was a C geek...

Nicholas Paul Johnson wrote:

>Hello all,
>
>As I'm learning Ruby, I've decided to write a few programs in Ruby to get
>a feel for the language.
>
>I've been a C programmer for a long time.  As such, I worry that I'm
>thinking too much like a C programmer, and not like a Ruby programmer...
>
>My first attempt has been an emulator for a cs-toy processor called IBCM 
>(itty-bitty computing machine).  Its spec (only 5 pages) is available at: 
>http://www.cs.virginia.edu/~cs216/notes/ibcm-poo.pdf
>
>I've written it, and it works correctly when compared to my program 
>written in C, but at its core is a large case-when-end statement.  
>This is not `sexy.'  I was wondering if there was a better way to do 
>this in Ruby, or if I'm just missing the point.
>
>My code is at: http://manjac.ath.cx/nick/ruby-ibcm.rb
>
>Thanks all,
>  
>
I haven't got any advice over what everyone else has suggested for the 
layout of your program but I have spotted a couple of bugs.

Firstly the read word instruction doesn't work. It either doesn't take 
any input or if you run the program with the trace option it gives an 
error no such file or directory - -t

changing the line
accum = gets.to_i

to

accum = $stdin.gets.to_i

fixes this

The other problem is the JUMPL instruction jumps even if the acummalator 
isn't less than 0. The problem is in this line

progcount = off  if accum & 0x8000

since 0 is a true value in Ruby the part accum & 0x8000 is always true. 
You need to change it to

progcount = off if (accum & ox8000 != 0)

--
Mark Sparshatt