Doing math in Ruby

ruby-talk
1

Hello everybody. I am new to Ruby and understand the bare minimum of
basic concepts. I was wondering if there was a way to take the input of
a user (supposedly a mathematical equation) and return the answer. For
example, if I started the Ruby script in my Terminal, is there a way
that I would be able to type in 1+2 and get a returned answer of 3?
Something I tried was:

puts "Enter Equation"
answervar = gets.chomp
doneans = answervar.to_i
puts doneans

Yet, all that did was return the first number of the equation. Any help
or advice would be greatly appreciated. Thanks!

···

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Posted via http://www.ruby-forum.com/.

2

Yet, all that did was return the first number of the equation.

···

===
to_i(base=10) → integer

Returns the result of interpreting leading characters in str as an
integer base base (between 2 and 36). Extraneous characters past the end
of a valid number are ignored. If there is not a valid number at the
start of str, 0 is returned.

puts "1abc".to_i
puts "abc1".to_i

--output:--
1
0

What you are trying to do is more complicated. You have to examine each
character in the string and try to decide what it is: a number or an
operator.

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Posted via http://www.ruby-forum.com/\.

3

This is not simple. Try simpler.

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···

On 07/09/2012, at 11:52 AM, "Jon M." <lists@ruby-forum.com> wrote:

Hello everybody. I am new to Ruby and understand the bare minimum of
basic concepts. I was wondering if there was a way to take the input of
a user (supposedly a mathematical equation) and return the answer. For
example, if I started the Ruby script in my Terminal, is there a way
that I would be able to type in 1+2 and get a returned answer of 3?
Something I tried was:

puts "Enter Equation"
answervar = gets.chomp
doneans = answervar.to_i
puts doneans

Yet, all that did was return the first number of the equation. Any help
or advice would be greatly appreciated. Thanks!

--
Posted via http://www.ruby-forum.com/\.

4

If it's just a tool for you to use, then I'd just eval the inputs (does
constrain the syntax a bit, though)

If you want to take in user input, then you'll need to do some kind of
parsing of the input. A quick search found
Math Parser, Part 4: Tests - Lukasz Wrobel which looks pretty
simple, but might work. Otherwise, try searching through rubygems.org and
ruby-toolbox.com

···

On Thu, Sep 6, 2012 at 8:52 PM, Jon M. <lists@ruby-forum.com> wrote:

Hello everybody. I am new to Ruby and understand the bare minimum of
basic concepts. I was wondering if there was a way to take the input of
a user (supposedly a mathematical equation) and return the answer. For
example, if I started the Ruby script in my Terminal, is there a way
that I would be able to type in 1+2 and get a returned answer of 3?
Something I tried was:

puts "Enter Equation"
answervar = gets.chomp
doneans = answervar.to_i
puts doneans

Yet, all that did was return the first number of the equation. Any help
or advice would be greatly appreciated. Thanks!

--
Posted via http://www.ruby-forum.com/\.