From: Matthew Harris <shugotenshi@...>
Date: 2007-12-23T04:33:48+09:00
Subject: Re: Diagnosing error in command line input

Dave Thacker wrote:
> I'm working on a program (my first) that will need to read user input (a file 
> name) from the command line.  While looking for examples of reading command 
> line input, I stumbled across this example(1) which I've cut and pasted, to 
> see how it works.  
> #!/usr/bin/ruby
> require 'readline'
>
> def prompt(prompt="> ")
>   input = nil
>   prompt += " " unless prompt =~ /\s$/
>   loop do
>     input = Readline.readline(prompt, true)
>     break if input.length > 0
>   end
>   return input
> end
>
> apples = prompt("how many apples do you have?")
> pears = prompt("how many pears do you have?")
> nonsense = prompt("try my input history (up/down arrow)")
>
> printf "there are %d items in our input history\n",
>        Readline::HISTORY
>
> When I run this I get:
> dthacker@buckbeak:~/learning/ruby$ ./test-cl-io.rb
> how many apples do you have? 3
> how many pears do you have? 7
> try my input history (up/down arrow) 5
> ./test-cl-io.rb:18:in `printf': can't convert Object into Integer (TypeError)
>         from ./test-cl-io.rb:18
>
> I'm guessing that HISTORY is not the method I want to call.  Is that my 
> problem?  Or is there a simple newbie syntax error I'm making?  
> TIA   
> Dave
>
> (1)http://beaver.net/slides/ruby/10-easy-pieces.html
>
>
>
>   
The object pointed to by Readline::HISTORY is not an object that can be 
converted to an Integer.  Your printf attempts to convert it to an 
integer because it has %d.  The Readline::HISTORY object is closer to an 
array.

Try the following:

printf "there are %d items in our input history\n", Readline::HISTORY.size


-- 
Matthew Harris
http://matthewharris.org