When I run this script:
pi=3.14
NozzleAreaM=.005**2*pi.to_f
It returns 7.85e-05 instead of 0.000078 like it does on a normal calculator. I've looked everywhere and I can't find a fix to this problem.
You just need to tell ruby in what format you want to display the float:
pi = 3.14
nozzle_area = 0.005**2 * pi
printf "%.8f \n", nozzle_area
--output:--
0.00007850
See prinf/sprinf here:
http://www.ruby-doc.org/core-2.2.0/Kernel.html#method-i-sprintf
Note that displaying a float in a certain format does not affect how ruby stores the float internally.
Also, writing code like this is fine:
pi=3.14
NozzleAreaM=.005**2*pi.to_f
...as long as you never need to show your code to anyone else. If you want to ask questions about your code, then you need to write legible code. That means you should NOT cram every thing together with no spaces.
In addition, variables that start with a capital letter are constants in ruby. If you do not know what that means yet, just live by this rule: do not capitalize any of your variable names.
Also, your pi variable is already a float (because it has a decimal point), so calling to_f() is unnecessary.
Also, ruby provides pi as a constant in the Math module(the Math module is required automatically):
nozzle_area = 0.005**2 * Math::PI
printf "%.8f \n", nozzle_area
--output:--
0.00007854
Related
I was doing a code golf (use the minimum number of characters) and I had the following working Python solution. I was trying to shorten my code by re-writing it to Ruby but my Ruby code would always print false.
The code had to read two strings, to ignore the case and to tell whether it was possible to obtain one string by rotating the other string. The output had to be either true or false. Do you have any idea what I did wrong in Ruby?
Python 3 (64 characters) - Works
a=input().lower()
b=input().lower()
print(str(a in 2*b).lower())
Ruby (47 characters) - Always prints "false"
a=gets.upcase
b=gets.upcase
p (b*2).include? a
With the examples I can think of, the Ruby code works correctly, but for some reason, it didn't work on the code golf site (codingame.com, the problem was proposed by user "10100111001").
In Ruby gets includes the \n at the end. You'd have to .chomp it away before doing anything.
a=gets.chomp.upcase
b=gets.chomp.upcase
p (b*2).include? a
By the way, this is not the right way to "tell whether it was possible to obtain one string by rotating the other string", it only partially solves the problem, hope you know that.
I'm trying to make a "complex calculation" in a freemarker template. The calculation calls for a modulus call. At first I kept simplifying my code, and finally just hardcoding values to try and figure out the cause, but it seems that freemarker's mod function ALWAYS returns int values?? but they're not even rounded, they're truncated. I need them rounded (.5 up would work). My most simplified code that does NOT work is this:
<#assign p_year_m1 = (2503.638 % 7.00)?float>
the longer version is:
<#assign p_year_m1 = ((bdy_m1 + (bdy_m1/4.0)-(bdy_m1/100.0)+(bdy_m1/400.0)))%7>
So the correct answer should be 4.638, rounds up to 5, but I'm getting 4.00 even if I wrap ?string[0.00] around it.
What am I missing? Surely there has to be a way to make this work! If not, I guess I'd need help constructing a work around to get similar results.
Thanks.
PS - the var, p_year_m1 is not intialized before this, so I believe if I try to store a float in there it should hold a float.
This is the calculation I'm trying to replicate
I can confirm that % gives the remainder of integer division. It casts (truncates) both arguments to integers, and then calculates the remainder. It's weird for sure, but can't be changed because of backward compatibility. The main application is calculating "zebra tables" and such, where it's might as well desirable, I don't know... it had just get in like that in the early times of the project, and then stuck.
i have the below actionscript and looking for the equivalent ruby on rails code to do the same job.
where dbwall and db_wall = 50
var tb= Math.pow((1/10),(dbwall)/(10));
Currently i have used:
#tb = ((1/10) ** (db_wall)/10)
and get 0.0, which is not what i need:
however in actionscript the actual answer to this is 0.00001
Is it just a case of the correct formula but not showing decimal places? or is there more to it than that?
Integer division in Ruby returns an integer (like C) so 1/10 equals 0. To get Float division, explicitly make one of the operands a Float e.g. 1.0/10
You don't need to include a few of the brackets too.
#tb = ((1/10) ** db_wall/10)
Would simply work. I wouldn't make this variable accessible to the view by using # if you carry on, just take that off and use it in future calculations.
What Max has answered would be the best answer to this simple problem.
this is my first post here. I started using Ruby just 2 days ago and think it is an amazing language, however I have been getting stuck. My problem is I am wanting to calculate the event horizon of a black hole given an input defined in the code as "m" This will then be put into a calculation and the size then printed out to the screen. I did need it to be in binary and thats where I am having the issue.
Here is my code so far.
#Event Horizon Calculation Program
G = 6.67*10**-11
m = 20
C = 200000
R = G*m/(C**2)
puts "Here is the result in Binary."
R.to_i(2)
puts R
Now I do realise that the number are not accurate, that dosen't matter at the moment. I just need the function to work.
Thankyou,
Ross.
Your post is not even in a format of asking a question, but guessing from what you wrote, it seems that you are asking how to change your code so that it accepts an input to m and outputs the result. My answer is based on this assumption.
In order to take an input, use the 'gets' method. So, you may want to replace your 'm = 20' line with:
m = gets.to_f
'gets' accepts an input as a string, so you need to convert it to a numeric. to_f changes a string into a float. You can use to_i instead if you want an integer.
You have a line 'R.to_i(2)', and it seems like you want to output this, but you have two problems here. First of all, whatever that creates, it is only creating something in that position, and does not change the value of R, so, in effect, it actually does nothing. Second, ruby can accept numerals in source code written in different bases such decimal, binary, hex, etc., but it only has one internal representation, and you cannot output a numeral in binary. For your purpose, you need to convert it to a string that corresponds to a binary expression. For that, use the 'to_s' method. In fact, the 'to_i' method does not take an argument. Delete your line 'R.to_i(s)', and replace the line 'puts R' with:
puts R.to_s(2)
The following piece of code works perfectly in script/console but returns the following error when i compile the same in a ruby script.:
:in `round': wrong number of arguments (1 for 0) (ArgumentError)
tf={"ph"=>{0=>1.33333333333333, 1=>1.5}, "fee"=>{0=>1.66666666666667}, "test"=>{0=>1.16666666666667, 1=>1.25}, "what"=>{0=>2.0, 1=>2.0}, "for"=>{0=>1.5}, "is"=>{0=>1.83333333333333, 1=>1.75}}
tf.each{|k,v| v.each{|k1,v1| tf[k][k1]=(v1.round(5))}}
Any Ideas ? Cheers !
Float#round seems to work differently in Ruby 1.8 and Ruby 1.9: in 1.8 it complains about the given argument, in 1.9 returns back float properly rounded to the given number of decimals.
But, as the article linked in the other answer wisely says:
you should consider the reason you’re
performing the rounding (or
equivalent) operation. If it’s for
presentation reasons only a better way
might be to use a format string
instead, and leave the original data
intact.
From what it looks like, you are not supposed to pass an argument to the round method. You have passed 5 to it.
If you are trying to round it to 5 decimal places, there is no builtin method for that (that I'm aware of). This is a page that explains how to do so: http://solutions.hans-eric.com/rounding-off-floating-point-numbers-in-ruby