Unexpected sprintf/String % Behavior

[Ben Gribaudo]

Hello,

I am puzzled by some strange (to me) behavior exhibited by String's %
method as well as sprintf. Both "%02d" % "07" and sprintf("%02d","07")
output "07". However, "%02d" % "08" and sprintf("%02d","08") both raise
'ArgumentError: invalid value for Integer: "08"'. Why does a string of
"07" work while "08" does not?

This is true when I test this on a MS Windows XP Pro box running Ruby
1.6.8 and when I test it on a Debian Woody box (kernal 2.4.19) running
Ruby 1.8.2. IRB examples and results are below.

Thank you,
Ben

Win XP box
-------------
irb(main):014:0> "%02d" % "07"
=> "07"
irb(main):015:0> "%02d" % "08"
ArgumentError: invalid value for Integer: "08"
from (irb):15:in `%'
from (irb):15
irb(main):017:0> sprintf("%02d","07")
=> "07"
irb(main):018:0> sprintf("%02d","08")
ArgumentError: invalid value for Integer: "08"
from (irb):18:in `sprintf'
from (irb):18

Linux box
----------
irb(main):003:0> "%02d" % "07"
=> "07"
irb(main):004:0> "%02d" % "08"
ArgumentError: invalid value for Integer: "08"
from (irb):4:in `%'
from (irb):4

irb(main):005:0> sprintf("%02d","07")
=> "07"
irb(main):006:0> sprintf("%02d","08")
ArgumentError: invalid value for Integer: "08"
from (irb):6:in `sprintf'
from (irb):6

 

[Gennady Bystritksy]

Hello,

I am puzzled by some strange (to me) behavior exhibited by String's %
method as well as sprintf. Both "%02d" % "07" and sprintf("%02d","07")
output "07". However, "%02d" % "08" and sprintf("%02d","08") both raise
'ArgumentError: invalid value for Integer: "08"'. Why does a string of
"07" work while "08" does not?

Because leading 0 makes your argument string be interpreted as an octal
number, where '8' is not a valid digit (0..7 are valid in base 8).

Hope it helps.
Gennady.

 

[Ara.T.Howard]

Hello,

I am puzzled by some strange (to me) behavior exhibited by String's % method
as well as sprintf. Both "%02d" % "07" and sprintf("%02d","07") output "07".
However, "%02d" % "08" and sprintf("%02d","08") both raise 'ArgumentError:
invalid value for Integer: "08"'. Why does a string of "07" work while "08"
does not?

leading zeros (as in c) mean octal. so there is no 08. only

00 01 02 03 04 05 06 07

the number eight being 10

for instance

harp:~ > irb
irb(main):001:0> 010
=> 8

irb(main):002:0> 017
=> 15

irb(main):003:0> 08
SyntaxError: compile error
(irb):3: Illegal octal digit
from (irb):3


not that you also have hex and binary literals like

0xa
0b101010

hth.


-a
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[Ben Gribaudo]

Thank you for explaining this.

Ben