Working on E2.java

Note that I will not necessarily attempt to fix all errors
at once. Instead, I will work on groups of errors at each
step, gradually whittling down the list. This is generally
a good strategy given that some errors might be really caused
by other errors: get rid of one error and others *might*
disappear.

I am using the Build Output tab at bottom of JCreator to get
more useful debugging info, i.e., a pointer into the line where
the compiler thinks the problem is.

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Error: V:\java-problems\E2-solution.java:20: illegal start of expression
                        value = binary_digit * 2**exponent;
                                                 ^
Cause: use of ** for exponentation.

Explanation: the compiler thought that the two *s were meant to be two separate multiplies.

Fix: changed to (int)Math.pow( 2, exponent ).

=======================================================

Error: cannot resolve symbol variable <name> (multiple errors on lines 16,17, 20, 21).
       Choosing one:
       
        V:\java-problems\E2-solution.java:21: cannot resolve symbol
	symbol  : variable decimal_number 
	location: class BinaryToDecimal
	                decimal_number = decimal_number + value;
                        ^
Cause: must declare the type of a variable before you use it.

Explanation: compiler was looking for something like "int decimal_number;" before this line.

Fix: in this case, we need to both declare the type *and* give it an initial value of 0.
     Provide declarations for all the variables listed in the error.

=======================================================

Error: V:\java-problems\E2-solution.java:29: decimal_number is already defined in main(java.lang.String[])
                int decimal_number =  (int)Math.pow(2, exponent);
                    ^
       
Cause: can't declare a variable twice. 

Explanation: I added "int decimal_number = 0;" above the loop. But now I have this
             other declaration below the loop. Can't have both.

Fix: get rid of the code at end of loop - it was just for demo purposes.

=======================================================

Error: none at this point: compiles fine.

The only problem is that there is no output of sum after loop
completes. Once this is added, works fine.