Feature #12968: Allow default value via block for Integer(), Float() and Rational()

• Status: Open
• Assignee: -
• Target version: -

[sos4nt (Stefan Schüßler)]

Kernel provides the global conversion functions Integer(), Float() and Rational(). Each one convert its argument to the respective type.

Parsing errors are signaled by raising a TypeError or an ArgumentError.

I often use these methods to parse numeric string values, but I find the need for a rescue ArgumentError block quite annoying an distracting.

I therefore request a new feature: Integer(), Float() and Rational() should take an optional block that serves as a callback when parsing failed.

Examples:

Integer('foo')                #=> ArgumentError  (just as before)
Integer('foo') { 0 }          #=> 0              (same as 'foo'.to_i)
Integer('foo') { nil }        #=> nil
Integer('foo') { Float::NAN } #=> NaN

This resembles the way Hash#fetch or Hash#fetch_values work when a block is given.

Although not used in the examples above, any arguments should be passed along to the block, i.e. Integer('foo') { |arg, base| ... }

[mudasobwa (Alexei Matyushkin)]

Stefan Schüßler wrote:

Integer('foo') { 0 }          #=> 0              (same as 'foo'.to_i)

To make it possible to fallback to e.g. #to_i it would be great to receive an actual argument as block parameter:

#                ⇓⇓⇓⇓⇓
Integer('foo') { |val| val.to_i }

[shyouhei (Shyouhei Urabe)]

• Related to Feature #12732: An option to pass to `Integer`, `Float`, to return `nil` instead of raise an exception added

[sos4nt (Stefan Schüßler)]

Alexei Matyushkin wrote:

To make it possible to fallback to e.g. #to_i it would be great to receive an actual argument as block parameter:

Absolutely, I've mentioned that in the last sentence.

[shyouhei (Shyouhei Urabe)]

+1 I like this idea. It must also be backwards compatible.

[nobu (Nobuyoshi Nakada)]

Only "invalid value for Integer()" from a string?
Integer can raise exceptions other than ArgumentError against a string, for example.

Integer(nil)           #=> can't convert nil into Integer (TypeError)
Integer(Object.new)    #=> can't convert Object into Integer (TypeError)
Integer(Object.new, 2) #=> base specified for non string value (ArgumentError)
Integer("", 1)         #=> invalid radix 1 (ArgumentError)
X=Struct.new(:to_i)
Integer(X.new("a"))    #=> can't convert #X to Integer (X#to_i gives String) (TypeError)

[sos4nt (Stefan Schüßler)]

Nobuyoshi Nakada wrote:

Only "invalid value for Integer()" from a string?

I don't have a strong opinion on this.

[shyouhei (Shyouhei Urabe)]

We looked at this issue at yesterday's developer meeting.

People there argued that explicit keyword argument is much easier to read than passing a block. They say it is not obvious what the block is going to do. So if the OP is OK we would like to to merge this issue with #12732. How do you feel, Stefan?

[sos4nt (Stefan Schüßler)]

shyouhei (Shyouhei Urabe) wrote:

we would like to to merge this issue with #12732. How do you feel, Stefan?

I'm fine with with that.