There are two programming language environments, or better to say operating systems, that are designed for this kind of immediate coding: Forth and Smalltalk. Forth plays its strength when controlling hardware. Your code is immediate executed, and you see the results, e.g. a robot arm moving instantly. Times of Forth coders running circles around teams using traditional programming languages are nearly over.

Smalltalk on the other hand still has to find its killer application. Smalltalk was 35 years to early, and since then every few month a new language is hyped, each one one step closer to Smalltalk. Computing history turns in cycles and we soon will have a situation comparable to VM/370, where every application is running its own operating system. I hope that there will be a Smalltalk killer application exploiting the immediate changes in coding to power users, similar as Forth controllers do, but on GUI level.