Data update

Task/Parsing-RPN-calculator-algorithm/Crystal/parsing-rpn-calculator-algorithm.cr

@@ -0,0 +1,26 @@
+def rpn_calc (tokens)
+  stack = [] of Float64
+  tokens.each do |token|
+    if token.is_a?(Float64)
+      stack.push token
+    else
+      x = stack.pop
+      y = stack.pop
+      case token
+      when "+" then stack.push(y + x)
+      when "-" then stack.push(y - x)
+      when "*" then stack.push(y * x)
+      when "/" then stack.push(y / x)
+      when "^" then stack.push(y ** x)
+      else raise "unknown operator: #{token}"
+      end
+    end
+    puts "%4s  %s" % {token, stack}
+  end
+end
+
+def tokenize (s)
+  s.split.map {|t| t.to_f rescue t }
+end
+
+rpn_calc tokenize "3 4 2 * 1 5 - 2 3 ^ ^ / +"