Convert 125% into 1.25?

Ruby
1

irb(main):011:0> format("%.2f",125)
=> “125.00”
irb(main):012:0> format("%.2f",125%)
SyntaxError: compile error
(irb):12: syntax error, unexpected ‘)’

2

From a mathematical aspect the % sign means 1/100 so 125 % equals
1.25.

Pen T. schrieb (am 21.8.10 07:16):

irb(main):011:0> format("%.2f",125)
=> “125.00”

irb(main):012:0> format("%.2f",125%)
SyntaxError: compile error
(irb):12: syntax error, unexpected ‘)’

Ruby does not allow you to write 125% like that.
You can however divide 125 by 100 (or rather 100.0 to get a
floating point number):

format( “%.2f”, 125 / 100.0 )
=> “1.25”

Regards,
Philipp

3

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Pen,

On Saturday 21 August 2010, Pen T. [email protected] wrote:

irb(main):012:0> format(“%.2f”,125%)

125% is, strictly spoken, not a number, but a number plus a unit. The
unit
is a character, not an integer, and this makes “125%” only valid as a
string
in Ruby. You’ve got to remove the “%” sign before you can treat “125” as
a
number.

HTH.

  Eric

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4

On Aug 22, 2010, at 13:32 , Dick D. wrote:

?> class Fixnum

def percent

the appropriate place to put that is Integer, not Fixnum.

5

You can sort of cheat, thanks to Rubys open classes.
Just add a method to Fixnum:

~:) irb

?> 100.class
=> Fixnum

?> class Fixnum

def percent
return self.to_f / 100
end
end
=> nil

?> 100.percent
=> 1.0

125.percent
=> 1.25

quit
~:)

This is pretty evil, though :slight_smile:

It is actually possible to define a method called ‘%’, but then you have
to call it as

100.%()

which looks awful.

On Sat, Aug 21, 2010 at 1:58 PM, Eric MSP Veith

6

On Aug 22, 2010, at 7:59 PM, Ryan D. wrote:

On Aug 22, 2010, at 13:32 , Dick D. wrote:

?> class Fixnum

def percent

the appropriate place to put that is Integer, not Fixnum.

% ruby -e ‘p 100.class.superclass’
Integer

Or even Numeric:

irb> 1.class.ancestors
=> [Fixnum, Integer, Numeric, Comparable, Object, Kernel, BasicObject]
irb> class Numeric
irb> def percent
irb> self.to_f / 100.0
irb> end
irb> end
=> nil
irb> 5.percent
=> 0.05
irb> 125.percent
=> 1.25
irb> 14.7.percent
=> 0.147
irb> (99+“44/100”.to_r).percent
=> 0.9944

-Rob

Rob B.
[email protected] http://AgileConsultingLLC.com/
[email protected] http://GaslightSoftware.com/

7

Ah, good catch both, thanks.

On Mon, Aug 23, 2010 at 2:02 AM, Rob B.

8

On Mon, Aug 23, 2010 at 8:22 AM, Ryan D.
[email protected]wrote:

On Aug 22, 2010, at 18:02 , Rob B. wrote:

Or even Numeric:
irb> class Numeric
irb> def percent
irb> self.to_f / 100.0
irb> end
irb> end
…

I said Integer because of how the original problem was described. I
thought

about floats and decided quickly that it didn’t make sense… but looking at
your examples above, that actually works and reads pretty well.

As a suggestion, if Rational is being used maybe “override” that with
the
following to avoid rounding differences: typically interest rates as
percentages have the fractional part as 1/2, 3/4, 5/8, etc, so mostly do
get
“mapped” to “precise” floats, but there might be uses of 2/5, etc
class Rational
def percent; self / 100; end
end
class Integer
def percent; Rational( self, 100); end
end

9

On Aug 22, 2010, at 18:02 , Rob B. wrote:

=> nil
irb> 5.percent
=> 0.05
irb> 125.percent
=> 1.25
irb> 14.7.percent
=> 0.147
irb> (99+“44/100”.to_r).percent
=> 0.9944

I said Integer because of how the original problem was described. I
thought about floats and decided quickly that it didn’t make sense…
but looking at your examples above, that actually works and reads pretty
well.