Using Math Symbols Stored in an Array as a String

Question

I'm very new to Ruby and I'm trying to use math symbols that are stored in an array as strings to perform math. This is for a Reverse Polish Notation calculator I'm working on. For example:

var = ['1','2','+']

I've puzzled through enough regular expressions to figure out how to differentiate numbers from non-numbers in an if statement, but I'm trying to figure out how I could make the following work to produce -1.

var[0]  var[2] var[1]   #=>   1 - 2

Does anyone know how to change the string '-' back into the math symbol?

You cannot do it. "Math symbol" is not a Ruby object. In other words, there is no such thing within Ruby code. — sawa
– sawa, Commented Aug 21, 2013 at 6:07

cHao · Accepted Answer · 2013-08-21 05:53:10Z

4

'1'.to_i.send('-', '2'.to_i)
# => -1

send calls the first argument as a method on the object, with the remaining arguments as parameters.

edited Aug 21, 2013 at 5:53

cHao

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answered Aug 21, 2013 at 5:46

Santhosh

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Comments

Eamonn O'Brien-Strain · Accepted Answer · 2013-08-21 05:49:56Z

1

One way to do this is using the eval function

result = eval "#{var[0]} #{var[2]} #{var[1]}"

answered Aug 21, 2013 at 5:49

Eamonn O'Brien-Strain

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