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

Ruby
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:

2

On Thu, 6 Dec 2007, Peter B. 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

*t

–

3

On Dec 5, 2007, at 5:52 PM, Tomas P.'s Mailing L. wrote:

Well, of course it is. It has let me type. Is there anyway to make it
i[’&’].call
puts “Evaluating stack: #{s.pop}”

Gives:

-> Number:
123
-> Evaluating stack: 123

And this very similar code works just fine for me.

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

So I wonder: what in your code that you are not showing us is
messing you up?

Regards, Morton

4

On Dec 5, 4:30 pm, Peter B. [email protected] 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?

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

5

You need $stdin.gets

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

6

On Dec 6, 2:57 pm, Peter B. [email protected] wrote:

You need $stdin.gets

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

Posted viahttp://www.ruby-forum.com/.

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