Sorry for coming back to this so late. I forgot to subscribe to get updates via email and thought nobody had replied yet. Thank you for all the comments, I think I get the point.
I am coming from a python background and was and am still working with a module called Theano that provides automatic differentiation and is used a lot for neural networks. This module offers an environment variable (floatX) that lets me specify whether I want to use Float64 or Float32 all the way. My workflow would then be: Prototype with Float32 to get the speed benefit. When I want to have a more serious look at my results, I switch to Float64 to be safe. So I thought I'd ask this question and if it turns out that there is a switch like that in Julia, I could just use it. I do understand that this was just a convenient "hack" for me and it will definitely work without that functionality. But in case it existed but just wasn't documented, I thought I'd ask. Thank you a lot for your comments, Pontus' solution seems to cover my use case just fine, I think I'll go with that. Best, Hubert
