If it where me I'd store the value of PI as a structure containing an IEEE double, a decimal representation of, say, 100 digits and a pointer to a function to that can evaluate PI to an arbitrary precision.
Then I'd just just use PI as a symbol and do symbolic algebra for as long as possible. Don't evaluate it to anything until the user actually asks for a numeric representation. Once a numeric representation is required I'd pick a value from the above structure based on what has been asked for.
Then I'd just just use PI as a symbol and do symbolic algebra for as long as possible. Don't evaluate it to anything until the user actually asks for a numeric representation. Once a numeric representation is required I'd pick a value from the above structure based on what has been asked for.