Ask HN: How much code does a CS PhD write?

I'm considering going to graduate school to do research in functional programming. It's something that I want to learn at a very deep level, not just practically but theoretically as well. My concern is that as a graduate student I won't write much code. Is this true? If you've done a PhD, how confident did you feel in your overall programming abilities compared to before? I know a lot of theoretical CS is math and formal proofs. How much is implementation, especially in the area of FP/Haskell/type theory?