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efus

Sun Nov 30, 2008 3:44 pm


recursive function problem

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Hi, I am having some troubles with a recursive function.
The function needs to get a string as an input. The string contains both symbols and numbers. What the function does is doing some operation on the two children of a node, the node being the operation(+,-,*,/). 
The thing is, I need the function to return a double. This couses a problem since I cant just convert the string to a double becouse of the operators. 
This is the algoritm:

function Evaluate {
if node is an operator(+,-,*,/) then
    evaluate the right and left child
    apply the operator of the node to the two children
else if the node is a value then
    the result is the value



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Tony

Sun Nov 30, 2008 3:52 pm


RE:recursive function problem

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typecast the value to Double. Then you are always doing operations on two Double's, so you can just return the same type.

It doesn't make sense to convert a String, since "+" in Double is meaningless.


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Vermette

Sun Nov 30, 2008 6:18 pm


RE:recursive function problem

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In case you're not sure what Tony is referring to:

http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Double.html

Make note of the valueOf(String s) method.