Lambda funcs that call gets won't halt program execution?

ruby-talk
1

Once again, a problem with my Befunge interpreter. I'm trying to
implement the ~ and & functions - get a character and a number,
respectively. My & function looks like this:
instructions["&"] = lambda { print "Number: "; stack.push
gets().strip.to_i}

But it complains about gets() being nil. as soon as the function is run.
Well, of course it is. It has let me type. Is there anyway to make it
halt?

Why does Ruby keep picking on me? Oh, wait. The principle of least
surprise - all programming languages infuriate me, therefore it would
surprise me least if Ruby did too. :slight_smile:

Attachments:
http://www.ruby-forum.com/attachment/1108/befunge.rb

···

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2

This works for me:

i= {}
s=
i["&"] = lambda {
   print "Number: "
   s.push( gets().strip.to_i ) }

i['&'].call
puts "Evaluating stack: #{s.pop}"

Gives:

-> Number:
123
-> Evaluating stack: 123

*t

···

On Thu, 6 Dec 2007, Peter Bunyan wrote:

Once again, a problem with my Befunge interpreter. I'm trying to
implement the ~ and & functions - get a character and a number,
respectively. My & function looks like this:
instructions["&"] = lambda { print "Number: "; stack.push
gets().strip.to_i}

But it complains about gets() being nil. as soon as the function is run.
Well, of course it is. It has let me type. Is there anyway to make it
halt?

--
-----------------------------------------------------------
   Tomas Pospisek
   http://sourcepole.com - Linux & Open Source Solutions
-----------------------------------------------------------

3

If Ruby is invoked in this fashion
  ruby myprog.rb myfile
then gets reads from the file.
You need
  $stdin.gets

···

On Dec 5, 4:30 pm, Peter Bunyan <peter.bun...@gmail.com> wrote:

Once again, a problem with my Befunge interpreter. I'm trying to
implement the ~ and & functions - get a character and a number,
respectively. My & function looks like this:
instructions["&"] = lambda { print "Number: "; stack.push
gets().strip.to_i}

But it complains about gets() being nil. as soon as the function is run.
Well, of course it is. It has let me type. Is there anyway to make it
halt?

4

And this very similar code works just fine for me.

<code test.rb>
#! /usr/bin/env ruby -w
$stack =
$instructions = {}
instructions = $instructions
stack = $stack
require "xtest"
instructions["&"].call
p stack
</code>

<code xtest.rb>
instructions = $instructions
stack = $stack
instructions["+"] = lambda { |a, b| stack.push(a + b) }
instructions["-"] = lambda { |a, b| stack.push(b - a) }
instructions["&"] = lambda { print("Number: "); stack.push(gets.chomp.to_i) }
</code>

So I wonder: what in your code that you are _not_ showing us is messing you up?

Regards, Morton

···

On Dec 5, 2007, at 5:52 PM, Tomas Pospisek's Mailing Lists wrote:

On Thu, 6 Dec 2007, Peter Bunyan wrote:

Once again, a problem with my Befunge interpreter. I'm trying to
implement the ~ and & functions - get a character and a number,
respectively. My & function looks like this:
instructions["&"] = lambda { print "Number: "; stack.push
gets().strip.to_i}

But it complains about gets() being nil. as soon as the function is run.
Well, of course it is. It has let me type. Is there anyway to make it
halt?

This works for me:

i= {}
s=
i["&"] = lambda {
  print "Number: "
  s.push( gets().strip.to_i ) }

i['&'].call
puts "Evaluating stack: #{s.pop}"

Gives:

-> Number:
123
-> Evaluating stack: 123

5

You need $stdin.gets

William, you're a brilliant person. You win. You're wintastic, in fact.

···

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6

I've scratched my head because of this behavior, too.
It's amazing how something so obvious can cause so
much puzzlement.

···

On Dec 6, 2:57 pm, Peter Bunyan <peter.bun...@gmail.com> wrote:

> You need $stdin.gets

William, you're a brilliant person. You win. You're wintastic, in fact.
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