Sure it is useful to run code in your head. I didn't say we must not think through code.
But to unable to run actual code at all? Come on. Who learns programming that way?
> But to unable to run actual code at all? Come on. Who learns programming that way?
Edsger Dijkstra was a proponent of that approach i.e. develop program and proof by hand in a language for which there is no compiler/interpreter.
I wrote about it here - https://news.ycombinator.com/item?id=47985605
I don't think anyone suggested that.