Change a string to an integer, report an error if the string does not represent an integer?

[Randy Kramer]

Can anybody point me to a way to check if a string represents a valid integer
and then convert it to an integer?

It is very likely the string will contain leading zeros, and should not
contain any trailing non-numeric characters.

Per the documentation (pickaxe 2), to_i won't quite do it, it will just ignore
trailing non-numeric characters.

Thanks!

Randy Kramer

 

[Daniel Waite]

Can anybody point me to a way to check if a string represents a valid
integer
and then convert it to an integer?

It is very likely the string will contain leading zeros, and should not
contain any trailing non-numeric characters.

Per the documentation (pickaxe 2), to_i won't quite do it, it will just
ignore
trailing non-numeric characters.

match = '000345'.match(/^\d+$/) # MatchData
match[0] # "000345"

match = '0003b45aa'.match(/^\d+$/) # nil
match # nil

 

[Tim Hunter]

Can anybody point me to a way to check if a string represents a valid
integer
and then convert it to an integer?

It is very likely the string will contain leading zeros, and should not
contain any trailing non-numeric characters.

Per the documentation (pickaxe 2), to_i won't quite do it, it will just
ignore
trailing non-numeric characters.

Check out Kernel#Integer

 

[Stefano Crocco]

Alle gioved=EC 25 ottobre 2007, Randy Kramer ha scritto:

Can anybody point me to a way to check if a string represents a valid
integer and then convert it to an integer?

It is very likely the string will contain leading zeros, and should not
contain any trailing non-numeric characters.

Per the documentation (pickaxe 2), to_i won't quite do it, it will just
ignore trailing non-numeric characters.

Thanks!

Randy Kramer

Kernel.Integer can convert a string to a number raising an exception if it =
has=20
the wrong format. The only problem lies in the fact that it treats a string=
=20
with leading zeros as an octal number (for example, Integer("000123") gives=
=20
83). To avoid this, you can use gsub on the string:

Integer("000123".gsub(/^0+/,''))
=3D> 123

I hope this helps

 

[David A. Black]

Hi --

Can anybody point me to a way to check if a string represents a valid integer
and then convert it to an integer?

It is very likely the string will contain leading zeros, and should not
contain any trailing non-numeric characters.

Per the documentation (pickaxe 2), to_i won't quite do it, it will just ignore
trailing non-numeric characters.

There's a method called Integer (uppercase I and all). It blows up if
the string has extra stuff:

irb(main):001:0> Integer("0003")
=> 3
irb(main):002:0> Integer("0003a")
ArgumentError: invalid value for Integer: "0003a"


David

--
Upcoming training by David A. Black/Ruby Power and Light, LLC:
* Advancing With Rails, Edison, NJ, November 6-9
* Advancing With Rails, Berlin, Germany, November 19-22
* Intro to Rails, London, UK, December 3-6 (by Skills Matter)
See http://www.rubypal.com for details!

 

[Jim Clark]

match = '000345'.match(/^\d+$/) # MatchData
match[0] # "000345"

match = '0003b45aa'.match(/^\d+$/) # nil
match # nil

Integers can also be negative. Not sure if this applies to your case but
if so, change the regex to something like:

match = '-000345'.match(/^\-*\d+$/) # MatchData
match[0] # "-000345"

match = '000345'.match(/^\-*\d+$/) # MatchData
match[0] # "000345"

match = '0003b45aa'.match(/^\-*\d+$/) # nil
match # nil

Regards,
Jim

 

[7stud --]

Can anybody point me to a way to check if a string represents a valid
integer
and then convert it to an integer?

It is very likely the string will contain leading zeros, and should not
contain any trailing non-numeric characters.

Per the documentation (pickaxe 2), to_i won't quite do it, it will just
ignore
trailing non-numeric characters.

Thanks!

Randy Kramer


Integers can also be negative.

Integers can also have leading '+' signs.

Another way:


def valid_int?(str)
start = true

str.each_byte do |char|
if start
start = false
if char == ?+ or char == ?-
next
end
end

if char < ?0 or char > ?9
return false
end
end

return true
end

strings = ['0013abc', '0025', '-0030', '+051', '00-1', '-abc72']
strings.each do |str|
if valid_int?(str)
puts str.to_i
else
puts 'invalid int'
end
end

 

[7stud --]

str.each_byte do |char|
if start
start = false
if char == ?+ or char == ?-
next
end
end

if char < ?0 or char > ?9
return false
end
end

return true
end

strings = ['0013abc', '0025', '-0030', '+051', '00-1', '-abc72']
strings.each do |str|
if valid_int?(str)
puts str.to_i
else
puts 'invalid int'
end
end

--output:--
invalid int
25
-30
51
invalid int
invalid int

 

[Randy Kramer]

Daniel Waite wrote:

---<good stuff (in this and the other replies) omitted>----

Thanks to all who replied!

Randy Kramer

 

[Lloyd Linklater]

One caveat is that integers can have alpha characters in the string,
e.g. hex.


p '2a'.to_i(16) # => 42

 

[7stud --]

str.each_byte do |char|
if start
start = false
if char == ?+ or char == ?-
next
end
end

if char < ?0 or char > ?9
return false
end
end

return true
end

strings = ['0013abc', '0025', '-0030', '+051', '00-1', '-abc72']
strings.each do |str|
if valid_int?(str)
puts str.to_i
else
puts 'invalid int'
end
end

--output:--
invalid int
25
-30
51
invalid int
invalid int

Ugh. This is much faster:

strings = ['0013abc', '0025', '-0030', '+051', '00-1', '-abc72']

strings.each do |str|
if str.match(/^(\-|\+)?\d+$/)
puts str.to_i
else
puts "invalid int"
end
end

 

[David A. Black]

Hi --

Ugh. This is much faster:

strings = ['0013abc', '0025', '-0030', '+051', '00-1', '-abc72']

strings.each do |str|
if str.match(/^(\-|\+)?\d+$/)
puts str.to_i
else
puts "invalid int"
end
end

Although....

strings = ["0025\nhello"] # will print 25

You want \A and \z, rather than ^ and $.


David

--
Upcoming training by David A. Black/Ruby Power and Light, LLC:
* Advancing With Rails, Edison, NJ, November 6-9
* Advancing With Rails, Berlin, Germany, November 19-22
* Intro to Rails, London, UK, December 3-6 (by Skills Matter)
See http://www.rubypal.com for details!

 

[Robert Klemme]

Alle giovedì 25 ottobre 2007, Randy Kramer ha scritto:

Kernel.Integer can convert a string to a number raising an exception ifit has
the wrong format. The only problem lies in the fact that it treats a string
with leading zeros as an octal number (for example, Integer("000123") gives
83). To avoid this, you can use gsub on the string:

Integer("000123".gsub(/^0+/,''))
=> 123

I hope this helps

I'd rather do

Integer(s.sub(/\A([+-]?)0+(?=.)/, '\\1'))

because your regexp has some issues:

1. "+010" is unchanged and will yield 8 instead of 10

2. same for negative numbers

3. "00" will be converted to "" which will trigger an error

4. you use gsub although the regular expression can match only once

Subtle, subtle...

Kind regards

robert