convert String to range

[Abir B.]

Hi,
is there a way to convert a string to a range??
"(1..2)" ==> (1..2) ??
Another question, what's the translation of infinite in ruby??
thanks

 

[Thomas Wieczorek]

I tried to monkey patch the Range class, but it doesn't seem to work,
so I patched the String class:

class String
def to_range
case self.count('.')
when 2
elements = self.split('..')
return Range.new(elements[0].to_i, elements[1].to_i)
when 3
elements = self.split('...')
return Range.new(elements[0].to_i, elements[1].to_i-1)
else
raise ArgumentError.new("Couldn't convert to Range: #{str}")
end
end
end

p "1..2".to_range
p "1...2".to_range
p "1.2".to_range

output:
1..2
1..1
rng.test:11:in `to_range': undefined local variable or method `str'
for "1.2":String (NameError)
from rng.test:18

 

[Todd Benson]

Another question, what's the translation of infinite in ruby??
thanks

irb(main):001:0> 0 / 0.0
=> NaN
irb(main):002:0> 42 / 0.0
=> Infinity
irb(main):003:0> -42 / 0.0
=> -Infinity

You can also use the #nan? and #infinity? methods. AFAIK, this works
only with Floats and BigDecimals.

hth,
Todd

 

[Abir B.]

thanks a lot
I'll try it...

 

[Justin Collins]

Hi,
is there a way to convert a string to a range??
"(1..2)" ==> (1..2) ??
Another question, what's the translation of infinite in ruby??
thanks

Not recommended, but eval is always an option:

irb(main):001:0> r = eval("(1..2)")
=> 1..2
irb(main):002:0> r.class
=> Range
irb(main):003:0> r.to_a
=> [1, 2]

-Justin

 

[Ian Whitlock]

I tried to monkey patch the Range class, but it doesn't seem to work,
so I patched the String class:

I am not sure what the rules for the request should be, but

p "(1..2)".to_range # 0..2 original request
p "1.2 - 7.2 + 3".to_range # 1..0
p '"a".."c"'.to_range # 0..0

all produce things I wouldn't want.

I see Justin Collins got in the eval suggestion before I
finished looking at it. I note that

eval("1.....7")

causes a syntax mistake. Is there a way to handle syntax
problems parallel to execution errors?

Ian

 

[Justin Collins]

I am not sure what the rules for the request should be, but

p "(1..2)".to_range # 0..2 original request
p "1.2 - 7.2 + 3".to_range # 1..0
p '"a".."c"'.to_range # 0..0

all produce things I wouldn't want.

I see Justin Collins got in the eval suggestion before I
finished looking at it. I note that

eval("1.....7")

causes a syntax mistake. Is there a way to handle syntax
problems parallel to execution errors?

Ian

This is a pretty strange way to go about it, but it will work even in
the presence of errors:

require 'thwait'

def make_range(str)
r = nil
thr = Thread.new do
$SAFE = 4
begin
r = eval(str)
rescue
end
end

ThreadsWait.new(thr).all_waits

r.is_a?(Range) ? r : nil
end

p make_range("1.....7") # nil
p make_range("(1..2)") # 1..2
p make_range("1.2 - 7.2 + 3") # nil
p make_range('"a".."c"') # "a".."c"
p make_range("exit!") # nil
p make_range("load 'evilfile.rb'") # nil


For some reason, trying to use Thread.join will prevent the exception
handling from working.

-Justin