CompOrg Spring 2005

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+ Using the pow function (math library)

Question:

I was wondering if it was legal to use math.h's "pow(double, double)" function for the binary_to_int function. (I use it to calculate powers of two.) The reason for my concern is that the sample main.c code had several #includes, but math.h was not one of them.

Answer:

You can use math functions, we will make sure it is linked with -lm. You need to make sure <math.h> is included in your code.

Note that there are much easier ways (logic operations instead of using the pow function...).

+ Powers of 2 using logic operations?

Question:

How can I compute powers of 2 using logic operations?

Answer:

Recall that a left shift (of an integer) corresponds to doubling the value, so the expression x<<1 is just like x*2. Shifting to the left twice (x<<2) is like multiplying by 4 (2²). The expression 0x01 << n is computing 2ⁿ.

+ Re-submitting

Question:

I don't seem to be able to re-submit!

Answer:

It's fixed now.

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