Re: calculator program help

On Nov 15, 2011, at 11:05 AM, Sylvester Keil wrote:

>=20
> On Nov 14, 2011, at 10:23 PM, Trevor Daniels wrote:
>=20
>> I'm trying to make a simple RPN calculator that reads in regular
>> expressions from a file and evaluates them to execute code. Currently =
I
>> have these regular expressions stored in an array of class objects =
that
>> have 2 data objects (1. The regex itself and 2. The block of code =
that
>> should be executed when a match is found). An example of one of the =
read
>> in regex's is below:
>>=20
>> [0-9]+
>> lambda {|input| $myStack.push(input)}
>>=20
>> Now, I get input from the user and compare that string to all the
>> regular expressions in my array. When a match is found, the code is
>> evaluated. So far it is working by entering in input one by one. Code
>> and an example are below.
>>=20
>> while input =3D gets
>> for i in 0..$regexArray.length-1
>>   if ( input =3D~ Regexp.new($regexArray[i].regex) )
>>     eval($regexArray[i].code).call(input)
>>   end
>> end
>> end
>>=20
>> Example:
>> 5
>> 4
>> +
>> print
>>=20
>> will give "9" as it should. However, I want to make it so I can enter
>> input in one line like:
>> 5 4 + print
>>=20
>> I've tried matching the input string with the regex with: myMatch =3D
>> regex.match(input)
>> but when I enter a string such as "123 456" only the last part =
("456")
>> is matched when I need to first match the ("123"). Any help would be
>> appreciated.
>=20
> If your valid expressions contain no whitespace, you can split your =
input into individual tokens with split(/\s+/). As a minimal example, =
this works fine:
>=20
>=20
> q =3D []
> a =3D {
> 	/\d+/ =3D> ->(input) { q << input.to_i },
> 	/\+|-/ =3D> ->(op) { q.push(q.pop(2).reverse.reduce(op)) },
> 	/print/ =3D> ->(match) { puts q.pop }
> }
>=20
> DATA.each_line do |input|
>  input.split(/\s+/).each do |token|
>    code =3D a[a.keys.detect { |k| token =3D~ k }]
>    code.call(token) unless code.nil?
>  end
> end
>=20
> __END__
> 5 4 + print
> 5 4 - print
>=20
> Returns 9 and -1.

I've just realized, if you'd expect results 9 and 1 then just skip the =
#reverse call above ;-)