while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that
in ruby?
Thomas Jollans nospam@jollans.com writes:
while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that in
ruby?
As with many other languages, dividing an integer by an integer produces an
integer. Make at least one of them a floating point number and the returned
value will be floating point.
irb(main):001:0> 9.0 / 5
=> 1.8
irb(main):002:0> 9 / 5.0
=> 1.8
If your two values are stored in variables, then you can call “to_f” to
force them to be floating point, like this:
irb(main):003:0> x = 9
=> 9
irb(main):004:0> y = 5
=> 5
irb(main):005:0> x / y
=> 1
irb(main):006:0> x.to_f / y
=> 1.8
irb(main):007:0> x / y.to_f
=> 1.8
irb(main):008:0> x.to_f / y.to_f
=> 1.8
Jim
···
–
Jim Menard, jimm@io.com, http://www.io.com/~jimm/
“Even anarchists have an agenda.” – Keith Beal
9.0/5, 9/5.0 or 9.0/5.0
(i.e., force one to be non-integer)
···
— Thomas Jollans nospam@jollans.com wrote:
while learning ruby i wanted to program a simple fahrenheit to
celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do
that
in ruby?
Do you Yahoo!?
Yahoo! Platinum - Watch CBS’ NCAA March Madness, live on your desktop!
http://platinum.yahoo.com
You might be interested in this tutorial:
http://www.math.umd.edu/~dcarrera/ruby/0.3/
It’s a work in progress, but it’s quite useful already.
In particular, it covers problems such as the one you just described.
···
On Fri, Mar 21, 2003 at 03:18:59AM +0900, Thomas Jollans wrote:
while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that
in ruby?
–
Daniel Carrera
Graduate Teaching Assistant. Math Dept.
University of Maryland. (301) 405-5137
Hi,
···
At Fri, 21 Mar 2003 03:18:59 +0900, Thomas Jollans wrote:
while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that
in ruby?
require ‘rational’
Rational(9, 5)
–
Nobu Nakada
in ruby objects (every variable) knows it’s type. thus, to say
a = 9/5
in ruby, is to like saying
int a = (int)9/(int)5;
in C.
eg. the result on an int divided by an int is an int.
so in ruby, as in C, you will need to make sure you variables are typed
correctly, eg. as floats. something like this
def to_fahrenheit degrees_celsius
((9.0/5.0) * degrees_celsius.to_f) + 32.0
end
def to_celsius degrees_fahrenheit
(5.0/9.0) * (degrees_fahrenheit.to_f - 32.0)
end
p to_fahrenheit 0 # >> 32.0
p to_celsius 32 # >> 0.0
note that these methods return floats because at least one of the operands is a
float.
-a
···
On Thu, 20 Mar 2003, Thomas Jollans wrote:
while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that in
ruby?
–
Ara Howard
NOAA Forecast Systems Laboratory
Information and Technology Services
Data Systems Group
R/FST 325 Broadway
Boulder, CO 80305-3328
Email: ahoward@fsl.noaa.gov
Phone: 303-497-7238
Fax: 303-497-7259
====================================
Thomas Jollans wrote:
while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that
in ruby?
irb(main):001:0> require ‘mathn’
true
irb(main):002:0> 1/2
1/2
Thomas Jollans nospam@jollans.com wrote in message news:b5cvpg$vj7$04$1@news.t-online.com…
while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that
in ruby?
One way is to require the ‘mathn’ standard library.
irb(main):001:0> require ‘mathn’
true
irb(main):002:0> f = 63
63
irb(main):003:0> c = (5/9)*(f - 32)
155/9
irb(main):004:0> c.to_f
17.22222222
‘mathn’ gives you rationals, complex numbers, and matrices, and allows a
more natural notation for rationals than the ‘rational’ library does (so
5/9 is the rational number five-ninths). I always require mathn!
Regards, Bret
Bret Jolly (Jou Lii Bair)
http://www.rexx.com/~oinkoink/
Not to disparage Daniel’s fine tutorial in any way, but I also have a
tutorial you might find useful:
Best of luck,
Chris
···
----- Original Message -----
From: “Daniel Carrera” dcarrera@math.umd.edu
To: “ruby-talk ML” ruby-talk@ruby-lang.org
Sent: Thursday, March 20, 2003 10:22 AM
Subject: Re: Newbie question: 9/5=1 ?
On Fri, Mar 21, 2003 at 03:18:59AM +0900, Thomas Jollans wrote:
while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that
in ruby?
You might be interested in this tutorial:
http://www.math.umd.edu/~dcarrera/ruby/0.3/
It’s a work in progress, but it’s quite useful already.
In particular, it covers problems such as the one you just described.
–
Daniel Carrera
Graduate Teaching Assistant. Math Dept.
University of Maryland. (301) 405-5137
in ruby objects (every variable) knows it’s type. thus, to say
a = 9/5
in ruby, is to like saying
int a = (int)9/(int)5;
in C.
…
If you have something like
a = 9.0/5
in ruby, does the parser optimize that to 1.8, or does it actually do
the calculation as the script is being run?
···
Do you Yahoo!?
Yahoo! Platinum - Watch CBS’ NCAA March Madness, live on your desktop!
http://platinum.yahoo.com
What happens if you do this from an extension? Will it change the
behavior of other extensions without their knowledge? Is that a good
idea?
Paul
···
On Fri, Mar 21, 2003 at 04:05:42AM +0900, Joel VanderWerf wrote:
Thomas Jollans wrote:
while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that
in ruby?irb(main):001:0> require ‘mathn’
true
irb(main):002:0> 1/2
1/2
Michael Campbell wrote:
in ruby objects (every variable) knows it’s type. thus, to say
a = 9/5
in ruby, is to like saying
int a = (int)9/(int)5;
in C.
…
If you have something like
a = 9.0/5
in ruby, does the parser optimize that to 1.8, or does it actually do
the calculation as the script is being run?
Ruby can’t optimize, because a devious programmer might do this:
irb(main):001:0> class Float
irb(main):002:1> def /(n)
irb(main):003:2> 0
irb(main):004:2> end
irb(main):005:1> end
nil
irb(main):006:0> 9.0/5
0
Paul Brannan wrote:
···
On Fri, Mar 21, 2003 at 04:05:42AM +0900, Joel VanderWerf wrote:
Thomas Jollans wrote:
while learning ruby i wanted to program a simple fahrenheit to celsius
converter. for that i need 9/5 to be 1,8 (and not 1). how do i do that
in ruby?irb(main):001:0> require ‘mathn’
true
irb(main):002:0> 1/2
1/2What happens if you do this from an extension? Will it change the
behavior of other extensions without their knowledge? Is that a good
idea?
I guess extension writers should not rely on 1/2 == 0 .
Ruby can’t optimize, because a devious programmer might do this:
Ah yes, good point. Thanks.
···
Do you Yahoo!?
Yahoo! Platinum - Watch CBS’ NCAA March Madness, live on your desktop!
http://platinum.yahoo.com
Do you think this is reasonable?
What method should I call if I want integer division?
Paul
···
On Sat, Mar 22, 2003 at 04:37:40AM +0900, Joel VanderWerf wrote:
I guess extension writers should not rely on 1/2 == 0 .
Paul Brannan wrote:
···
On Sat, Mar 22, 2003 at 04:37:40AM +0900, Joel VanderWerf wrote:
I guess extension writers should not rely on 1/2 == 0 .
Do you think this is reasonable?
What method should I call if I want integer division?
Technically, it looks like you can call ‘div’, i.e. 9.div(5) will still
return the standard integer division result. But this is completely
non-obviously, and I only learned it after digging in the source code.
Supposedly, you have to use Kernel.Integer, which uses native
conversion if obj is builtin numeric object, otherwise it calls
obj.to_int (if obj responds to to_int, in Ruby 1.7 or later) or
obj.to_i (if obj does not respond to to_int, or Ruby version is older
than 1.7). For example, Rational class has Rational#to_i, which hides
the call of Integer#div.
FUKUMOTO Atsushi
fukumoto@imasy.or.jp
···
Paul Brannan pbrannan@atdesk.com wrote:
On Sat, Mar 22, 2003 at 04:37:40AM +0900, Joel VanderWerf wrote:
I guess extension writers should not rely on 1/2 == 0 .
Do you think this is reasonable?
What method should I call if I want integer division?