Lambda the Ultimate

Slide 19 of Andy Wingo’s The User in the Loop:

RDD: REPL-driven development

guile> (import (my-app))

Put the user in the [read-eval-print] loop

REPL provides discoverability and hackability

Compare this to page 1 of I Hate Forth by Jack Ganssle (Jul 2001):

Forth is a very satisfying environment for a programmer. It's totally interactive. The interpreter — which is generally quite small — lives in your target system. It's a bit like working with old-time Basic - change something and immediately test the new code. There's no compile, link or download. Adherents crow about how productive they are working with a tool like this that imposes no delays on their work.

Sure, it's fast. And fun. But let's get real: interactive development has no impact on requirements analysis, specification, software design, documentation, or even test. Fast tools make for fast debugging, nothing else.

How much time do we spend debugging: 80% of the project? I sure hope not. A well-designed, carefully coded system should consume no more than 20% of the schedule in debug. Healthy software organizations need less.

… how much time do we really save? … Minutes [per day], max.