# Code Critique: check if int or float

**URL:** <https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375>\
**Category:** Ruby\
**Created:** [June 21, 2007, 12:17am UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375 "2007-06-21T00:17:54Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![ole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/fbc32d/32.png) [@ole](https://www.ruby-forum.com/u/ole)\
**Post date:** [June 21, 2007, 12:17am UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375/1 "2007-06-21T00:17:54Z")

</div>

Hello again folks,

I’m really starting to like this language. I’m working towards building  
a simple expression evaluator. I couldn’t seem to find any methods for  
testing whether a string contains an integer or float. In PHP (where I’m  
from) you’ve got your is\_numeric(). Is there such a method in Ruby?

Anyway, under the assumption that there wasn’t and to learn a bit I  
decided to add the methods i? and f? to String. I was wondering if I  
could get a bit of a critique on this code because I’m still ultra new  
to Ruby.

# I’m a TDD maniac, so I’ve got miself a test case in there too:

class String

# Strict test whether the string is a valid integer

# Underscores are not permitted.

# allowScientific is false by default because “4e3”.to\_i is 4

def i?(allowScientific = false)  
if allowScientific  
return (self =~ /^-?\d+(e-?\d+)?$/) != nil  
end  
(self =~ /^-?\d+$/) != nil  
end

# Strict test whether the string is a valid float.

# i.e. 4 is not but 4.0 is. Scientific notation acceptable.

def f?(allowScientific = true)  
if allowScientific  
return (self =~ /^-?\d\*.\d+(e-?\d+)?$/) != nil  
end  
(self =~ /^-?\d\*.\d+$/) != nil  
end  
end

require ‘test/unit’

# class StringExtensionsTest \< Test::Unit::TestCase def testI assert ‘45’.i? assert ‘-3’.i? assert !‘3s’.i? assert !‘3\_000’.i? assert !‘3e3’.i? end def testIScientific assert !‘e4’.i?(true) assert ‘4e2’.i?(true) assert ‘-8e3’.i?(true) assert ‘-5e-25’.i?(true) end def testFBasic assert !‘3’.f?(false) assert ‘3.0’.f?(false) assert ‘-25.36’.f?(false) assert ‘.52’.f?(false) assert ‘-.14’.f?(false) end def testFScientific assert !‘e1’.f? assert !‘4e1’.f? assert ‘3.12e1’.f? assert ‘-2.0e-3’.f? assert ‘-.6e2’.f? end end

# 4 tests, 19 assertions, 0 failures, 0 errors

Final question, what are your feelings on camelCase and Ruby’s apparent  
shunning of it?

---

<div class="post-metadata">

**Author:** ![ole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/fbc32d/32.png) [@ole](https://www.ruby-forum.com/u/ole)\
**Post date:** [June 21, 2007, 12:29am UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375/2 "2007-06-21T00:29:54Z")

</div>

On Thu, Jun 21, 2007 at 07:17:53AM +0900, ole \_\_ wrote:

> I’m really starting to like this language. I’m working towards building  
> a simple expression evaluator. I couldn’t seem to find any methods for  
> testing whether a string contains an integer or float. In PHP (where I’m  
> from) you’ve got your is\_numeric(). Is there such a method in Ruby?
> 
> Anyway, under the assumption that there wasn’t and to learn a bit I  
> decided to add the methods i? and f? to String. I was wondering if I  
> could get a bit of a critique on this code because I’m still ultra new  
> to Ruby.

> > ‘3s’.to\_i  
> > =\> 3
> 
> > Integer(‘3s’)  
> > ArgumentError: invalid value for Integer: “3s”  
> > from (irb):3:in `Integer’  
> > from (irb):3
> 
> > ‘3s’.to\_f  
> > =\> 3.0
> 
> > Float(‘3s’)  
> > ArgumentError: invalid value for Float(): “3s”  
> > from (irb):5:in `Float’  
> > from (irb):5
> 
> > ‘-8e3’.to\_f  
> > =\> -8000.0
> 
> > Float(’-8e3’)  
> > =\> -8000.0
> 
> > ‘-8e3’.to\_i  
> > =\> -8
> 
> > Integer(’-8e3’)  
> > ArgumentError: invalid value for Integer: “-8e3”  
> > from (irb):9:in `Integer’  
> > from (irb):9

You could likely come up with a much cleaner implementation using  
Integer() and Float() + rescue ArgumentError.

And about camelCase, it’s true, almost no one in Ruby uses  
camelCase. I’d recommend just going with the flow and adoption  
lowercase\_and\_underscored.

marcel

---

<div class="post-metadata">

**Author:** ![ole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/fbc32d/32.png) [@ole](https://www.ruby-forum.com/u/ole)\
**Post date:** [June 21, 2007, 12:35am UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375/3 "2007-06-21T00:35:55Z")

</div>

ole \_\_ wrote:

> Hello again folks,
> 
> I’m really starting to like this language. I’m working towards building  
> a simple expression evaluator. I couldn’t seem to find any methods for  
> testing whether a string contains an integer or float. In PHP (where I’m  
> from) you’ve got your is\_numeric(). Is there such a method in Ruby?

The Integer() method raises an exception if its argument isn’t an  
integer:

Integer(“1”) is okay.  
Integer(“1.0”) raises ArgumentError.

Similarly Float() raises an exception if its argument isn’t a Float:

Float(“1.0”) is okay.  
Float(“1”) is okay.  
Float(“x”) raises ArgumentError.

---

<div class="post-metadata">

**Author:** ![ole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/fbc32d/32.png) [@ole](https://www.ruby-forum.com/u/ole)\
**Post date:** [June 21, 2007, 4:53pm UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375/4 "2007-06-21T16:53:42Z")

</div>

ole \_\_ wrote, On 6/20/2007 5:51 PM:

> > 
> 
> I won’t be so easily converted. It’s more characters, the character is a  
> stretch on the keyboard and they are harder to read. Underscores seem  
> backward to me.

I found that you pick them up quickly and it isn’t any harder than  
reaching for shift after a while - it’s just repetition that’s needed to  
memorize it. Besides that, generally I think its good to stick to the  
conventions of a particular community. So, when I write Java, I use  
Java conventions, and when I write Ruby, I use Ruby conventions.

It was weird at first, but I picked it up in no time.

---

<div class="post-metadata">

**Author:** ![ole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/fbc32d/32.png) [@ole](https://www.ruby-forum.com/u/ole)\
**Post date:** [June 21, 2007, 12:51am UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375/5 "2007-06-21T00:51:22Z")

</div>

Thanks Tim and Marcel.

Would you have thought String.i? and String.f? would make more sense  
than Integer() and Float(). But yeah they will probably make for a  
better implementation then the regexps.

> And about camelCase, it’s true, almost no one in Ruby uses  
> camelCase. I’d recommend just going with the flow and adoption  
> lowercase\_and\_underscored.

I won’t be so easily converted. It’s more characters, the character is a  
stretch on the keyboard and they are harder to read. Underscores seem  
backward to me.

---

<div class="post-metadata">

**Author:** ![ole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/fbc32d/32.png) [@ole](https://www.ruby-forum.com/u/ole)\
**Post date:** [June 21, 2007, 5:12pm UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375/6 "2007-06-21T17:12:49Z")

</div>

Hi –

On Thu, 21 Jun 2007, Sammy L. wrote:

> Besides that, generally I think its good to stick to the conventions of a  
> particular community. So, when I write Java, I use Java conventions, and  
> when I write Ruby, I use Ruby conventions.

That’s really the main point. It’s not a matter of being converted to  
using or not using camelCase – it’s a matter of being converted to  
the practice of following the stylistic conventions and traditions,  
whatever they may be. As a cellist I like using a bow, but when I  
play the piano I use my fingers 🙂

David

---

<div class="post-metadata">

**Author:** ![ole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/fbc32d/32.png) [@ole](https://www.ruby-forum.com/u/ole)\
**Post date:** [June 21, 2007, 6:44pm UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375/7 "2007-06-21T18:44:30Z")

</div>

Yes but /^\d+/ isn’t the same as /^-?\d+$/.

---

<div class="post-metadata">

**Author:** ![ole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/fbc32d/32.png) [@ole](https://www.ruby-forum.com/u/ole)\
**Post date:** [June 21, 2007, 6:58pm UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375/8 "2007-06-21T18:58:10Z")

</div>

On 6/21/07, ole \_\_ [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Yes but /^\d+/ isn’t the same as /^-?\d+$/.
> 
> –  
> Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/).

oops, well spotted, but that will not change a lot…

640/140 \> cat conversions.rb && ruby conversions.rb

# vim: sts=2 sw=2 tw=0 expandtab nu:

require ‘benchmark’

class String  
def int?  
/^-?\d+$/ === self  
end

def int1?  
Integer(self) rescue false  
end  
end  
N=10\_000  
Benchmark.bmbm do  
|bench|  
bench.report( “reg” ) { N.times{ |n| n.to\_s.int?; “#{n}x”.int? } }  
bench.report( “Int” ) { N.times{ |n| n.to\_s.int1?; “#{n}x”.int1? } }  
end

Rehearsal ---------------------------------------  
reg 0.160000 0.000000 0.160000 ( 0.188396)  
Int 0.440000 0.000000 0.440000 ( 0.467686)  
------------------------------ total: 0.600000sec

```
      user system total real

```

reg 0.160000 0.000000 0.160000 ( 0.193306)  
Int 0.430000 0.010000 0.440000 ( 0.465137)

---

<div class="post-metadata">

**Author:** ![ole](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/o/fbc32d/32.png) [@ole](https://www.ruby-forum.com/u/ole)\
**Post date:** [June 21, 2007, 6:26pm UTC](https://www.ruby-forum.com/t/code-critique-check-if-int-or-float/107375/9 "2007-06-21T18:26:58Z")

</div>

On 6/21/07, ole \_\_ [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Thanks Tim and Marcel.
> 
> Would you have thought String.i? and String.f? would make more sense  
> than Integer() and Float().  
> They are just not the same,  
> String#i? and String#f? which I would call String#int? and  
> String#float? might be nice for you. You can search the Ruby Change  
> Requests if this was braught up already.  
> It might be a nice thing to have a String#int? without converting  
> actually.  
> But yeah they will probably make for a  
> better implementation then the regexps.

Hmm not sure at all, let us see

637/137 \> cat conversions.rb && ruby conversions.rb

# vim: sts=2 sw=2 tw=0 expandtab nu:

require ‘benchmark’

class String  
def int?  
/^\d+/ === self  
end

def int1?  
Integer(self) rescue false  
end  
end  
N=10\_000  
Benchmark.bmbm do  
|bench|  
bench.report( “reg” ) { N.times{ |n| n.to\_s.int?; “#{n}x”.int? } }  
bench.report( “Int” ) { N.times{ |n| n.to\_s.int1?; “#{n}x”.int1? } }  
end

Rehearsal ---------------------------------------  
reg 0.160000 0.000000 0.160000 ( 0.201496)  
Int 0.420000 0.000000 0.420000 ( 0.466641)  
------------------------------ total: 0.580000sec

```
      user system total real

```

reg 0.180000 0.000000 0.180000 ( 0.238369)  
Int 0.420000 0.010000 0.430000 ( 0.513518)

actually the arithmetic part is too costy 😉

Cheers  
Robert  
–You see things; and you say Why?  
But I dream things that never were; and I say Why not?  
– George Bernard Shaw