# Interactive Mode BASIC Interpreter (#232)

**URL:** <https://www.ruby-forum.com/t/interactive-mode-basic-interpreter-232/188232>\
**Category:** Ruby\
**Created:** [May 8, 2010, 2:51am UTC](https://www.ruby-forum.com/t/interactive-mode-basic-interpreter-232/188232 "2010-05-08T02:51:16Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\
**Post date:** [May 8, 2010, 2:51am UTC](https://www.ruby-forum.com/t/interactive-mode-basic-interpreter-232/188232/1 "2010-05-08T02:51:16Z")

</div>

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## Interactive Mode BASIC Interpreter (#232)

Ellohay Rubyists,

This quiz is courtesy of Jean L…

This week’s quiz is to extend the BASIC interpreter from quiz  
#228[1][2] so that it can start in interactive mode.

In interactive mode, we should be able to type following commands:

- ‘load’ a program,
- ‘list’ the loaded file,
- ‘run’ it,
- ‘quit’ the interpreter,
- ‘debug’ the program.  
Once debugging, the user should be able to set breakpoints, display  
the active breakpoints, display a variable value or all the variables,  
remove breakpoints and step the program.

Optionally, breakpoints could be conditional, user could change the  
variable values, and more.

Have fun!

Code:  
[2]: [http://rubyquiz.strd6.com/quizzes/228\_Ruby\_Basic.zip](http://rubyquiz.strd6.com/quizzes/228_Ruby_Basic.zip)

---

<div class="post-metadata">

**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\
**Post date:** [May 20, 2010, 2:43am UTC](https://www.ruby-forum.com/t/interactive-mode-basic-interpreter-232/188232/2 "2010-05-20T02:43:34Z")

</div>

Daniel X Moore wrote:

> - ‘list’ the loaded file  
> Not quite sure what this means, but I took it to mean “display the path  
> of the loaded file”

I’m almost done, just working on debug now.

Right now it only has the commands run, list, help, debug, quit, unload,  
and load - should it be like irb? That’d be a lot harder…

Either way, I’ll repost it when debug is done (or maybe/probably I’ll  
never finish it, about to move to Canada for a while)

Delete everything after the “class BasicString” section and append the  
following code:

if $0 == **FILE**  
basic = BasicInterpreter.new  
if ARGV[0]  
basic.run\_file ARGV[0]  
else  
command\_list = {‘help’ =\> “receive ‘help’”, ‘quit’ =\> “‘quit’ the  
interpreter”, ‘load’ =\> “‘load’ a program”, ‘unload’ =\> “‘unload’ a  
program”, ‘run’ =\> “‘run’ the loaded file”, ‘list’ =\> “‘list’ the loaded  
file”, ‘debug’ =\> “‘debug’ the program”}  
puts ‘Ruby BASIC - Interactive Mode’  
loop do  
print '\>\> ’  
if((command = gets.chomp) == ‘’) then  
next  
end  
if((command[/ /].nil?)) then  
if(!(command\_list.has\_key?(command))) then  
puts ‘Invalid command - type “help commands” for help’  
next  
end  
else  
if(!(command\_list.has\_key?(command[/.+? /][/[^]+/]))) then  
puts ‘Invalid command - type “help commands” for help’  
next  
end  
end  
if(command[/.+? /] == 'help ’ || command == ‘help’) then  
if(command == ‘help’) then  
puts 'Ben R.‘s solution to Ruby Q. #232 - Interactive  
BASIC Interpreter’  
next  
end  
if(command == ‘help commands’) then  
print ‘The commands are: ’  
command\_list.each\_key{|a|print a+’ '}  
puts ‘(type "help " for more info)’  
next  
end  
if(command\_list.has\_key?(command[/ (._)/][/[^]+/])) then  
puts command\_list[command[/ (._)/][/[^]+/]]  
next  
end  
puts ‘That command does not exist.’  
next  
end  
if(command[/.+? /] == 'quit ’ || command == ‘quit’) then  
puts ‘Goodbye.’  
`pause >nul`  
Kernel.exit!  
end  
if(command[/.+? /] == 'load ’ || command == ‘load’) then  
if(command[/ /].nil?) then  
begin  
print 'Which file should I load? ’  
loaded\_file = gets.chomp  
end until(File.exists?(loaded\_file))  
puts “File ‘#{loaded\_file}’ loaded.”  
else  
if(File.exists?(command[/ .+/][/[^]+ ?([^]\* ?)_/])) then  
loaded\_file = command[/ .+/][/[^]+ ?([^]_ ?)_/]  
puts “File ‘#{loaded\_file}’ loaded.”  
else  
puts ‘File not found.’  
puts command[/ .+/][/[^]+ ?([^]_ ?)\*/]  
end  
end  
next  
end  
if(command[/.+? /] == 'unload ’ || command == ‘unload’) then  
if(command[/ /].nil?) then  
loaded\_file = nil  
else  
if(command[/.+? /][/[^]+/] == loaded\_file) then  
loaded\_file = nil  
else  
puts “I don’t have that file loaded!”  
puts "Loaded file: "+loaded\_file  
next  
end  
end  
next  
end  
if(command[/.+? /] == 'run ’ || command == ‘run’) then  
if(command[/ /].nil? && loaded\_file.nil?) then  
begin  
print 'Which file should I load and run? ’  
loaded\_file = gets.chomp  
end until(File.exists?(loaded\_file))  
elsif(loaded\_file.nil?)  
loaded\_file = command[/.+? /][/[^]+/]  
end  
puts “Running file ‘#{loaded\_file}’.”  
basic.run\_file(loaded\_file)  
next  
end  
if(command[/.+? /] == 'list ’ || command == ‘list’) then  
puts(loaded\_file || ‘No file loaded’)  
end  
if(command[/.+? /] == 'debug ’ || command == ‘debug’) then  
puts ‘Unsupported.’  
next  
end  
end  
end  
end

---

<div class="post-metadata">

**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\
**Post date:** [May 20, 2010, 9:47am UTC](https://www.ruby-forum.com/t/interactive-mode-basic-interpreter-232/188232/3 "2010-05-20T09:47:51Z")

</div>

On Thu, May 20, 2010 at 2:43 AM, Ben R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Daniel X Moore wrote:
> 
> > - ‘list’ the loaded file  
> > Not quite sure what this means, but I took it to mean “display the path  
> > of the loaded file”

I think it could mean “show the source”, maybe?

Jesus.

---

<div class="post-metadata">

**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\
**Post date:** [May 22, 2010, 3:01am UTC](https://www.ruby-forum.com/t/interactive-mode-basic-interpreter-232/188232/4 "2010-05-22T03:01:52Z")

</div>

Jesús Gabriel y Galán wrote:

> I think it could mean “show the source”, maybe?

I sort of thought that too, but I’ll just stick with what I have -  
someone can open their text editor of choice and view it there. Any  
input about irb/non-irb?

Thanks for replying 🙂

---

<div class="post-metadata">

**Author:** ![danmcb](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/13edae/32.png) [@danmcb](https://www.ruby-forum.com/u/danmcb)\
**Post date:** [May 23, 2010, 7:11pm UTC](https://www.ruby-forum.com/t/interactive-mode-basic-interpreter-232/188232/5 "2010-05-23T19:11:23Z")

</div>

Ben R. wrote:

> Jesús Gabriel y Galán wrote:
> 
> > I think it could mean “show the source”, maybe?
> 
> I sort of thought that too, but I’ll just stick with what I have -  
> someone can open their text editor of choice and view it there. Any  
> input about irb/non-irb?
> 
> Thanks for replying 🙂

The meaning of the ‘list’ command is indeed: show the code of the  
currently load basic script.

JEan