32 lines
1.2 KiB
Text
32 lines
1.2 KiB
Text
import "./seq" for Stack
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var rpnCalculate = Fn.new { |expr|
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if (expr == "") Fiber.abort("Expression cannot be empty.")
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System.print("For expression = %(expr)\n")
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System.print("Token Action Stack")
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var tokens = expr.split(" ").where { |t| t != "" }
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var stack = Stack.new()
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for (token in tokens) {
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var d = Num.fromString(token)
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if (d) {
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stack.push(d)
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System.print(" %(d) Push num onto top of stack %(stack)")
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} else if ((token.count > 1) || !"+-*/^".contains(token)) {
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Fiber.abort("%(token) is not a valid token.")
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} else if (stack.count < 2) {
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Fiber.abort("Stack contains too few operands.")
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} else {
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var d1 = stack.pop()
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var d2 = stack.pop()
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stack.push(token == "+" ? d2 + d1 :
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token == "-" ? d2 - d1 :
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token == "*" ? d2 * d1 :
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token == "/" ? d2 / d1 : d2.pow(d1))
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System.print(" %(token) Apply op to top of stack %(stack)")
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}
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}
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System.print("\nThe final value is %(stack.pop())")
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}
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var expr = "3 4 2 * 1 5 - 2 3 ^ ^ / +"
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rpnCalculate.call(expr)
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