Can't get my regexp to work to test if numerical

Ruby
1

alright, this seems easy enough.

Building a Bank class, deposits must be floating, so if it has any
letters, it will tell the user it needs numbers

     if amount == /^[0-9]$/
     deposit_to_acct(amount,current_account)
     puts 'You have deposited ' + amount.to_s

      else
      puts 'Must be a number, alphabet bank is next door to your

right’

    end

it goes straight to the else statement, never executes the
deposit_to_acct method.

What part am I doing wrong?

2

Feng T. wrote:

alright, this seems easy enough.

Building a Bank class, deposits must be floating, so if it has any
letters, it will tell the user it needs numbers

     if amount == /^[0-9]$/
     deposit_to_acct(amount,current_account)
     puts 'You have deposited ' + amount.to_s

      else
      puts 'Must be a number, alphabet bank is next door to your

right’

    end

  1. The pattern /^[0-9]$/ matches one digit.

  2. amount would have to be a regex object to == the regex on the right.

if ‘abc’ == /abc/
puts ‘yes’
else
puts ‘no’
end

regex_obj = /abc/

if regex_obj == /abc/
puts ‘yes’
else
puts ‘no’
end

–output:–
no
yes

3

On Nov 2, 2007, at 12:47 AM, Feng T. wrote:

right’

    end

it goes straight to the else statement, never executes the
deposit_to_acct method.

What part am I doing wrong?

I would say that you need a better understanding of regular
expressions and how they are matched to strings in Ruby. The expression

amount == /^[0-9]$/

is an equality test and will always be false if ‘amount’ is a string.
Consider the following examples:

# the following perform equality tests, not string to regular expression matching 123 == /^[0-9]$/ # => false '123' == /^[0-9]$/ # => false /^[0-9]$/ == /^[0-9]$/ # => true /^[0-9]$/.equal?(/^[0-9]$/ )# => false # the following perform regular expression matching '123' =~ /^[0-9]$/ # => nil (match fails because RE only accepts one digit) '3' =~ /^[0-9]$/ # => 0 (match succeeds) '123' =~ /^[0-9]+$/ # => 0 (match succeeds) '123X' =~ /^[0-9]+$/ # => nil (match fails)

Regards, Morton

4

7stud – wrote:

Feng T. wrote:

alright, this seems easy enough.

Building a Bank class, deposits must be floating, so if it has any
letters, it will tell the user it needs numbers

     if amount == /^[0-9]$/
     deposit_to_acct(amount,current_account)
     puts 'You have deposited ' + amount.to_s

      else
      puts 'Must be a number, alphabet bank is next door to your

right’

    end
  1. The pattern /^[0-9]$/ matches one digit.

That’s incorrect. The pattern matches: the start of the line, followed
by one digit, followed by the end of the line. So the regex won’t
match a digit in a line containing two digits:

regex = /^[0-9]$/

line = ‘8’
match_obj = regex.match(line)
p match_obj.to_a

line = ‘12’
match_obj = regex.match(line)
p match_obj.to_a

–output:–
[“8”]
[]

You certainly don’t have to use regex’s to convert a string to a float
(or an int). Look at String#to_f and Kernel.Float.