[jasomill]

Definitely my favorite programmable HP calculator — fully loaded with development tools, it's essentially a quirky handheld Lisp machine.

While the 15C is my "daily driver", my dream HP calculator is a 50G with an OLED display, styled to resemble the 48G[X].

[whartung]

> my dream HP calculator is a 50G with an OLED display,

This is why I use the app on my phone. I really can't use my normal one without a backlight any more, just too hard to read.

[tzs]

I'd like to see a phone case designed to make using a phone calculator easier.

There are at least three ways this could be done. The simplest would be a case that covers the part of the phone display where the calculator buttons are, with cutouts in the case that go over those buttons.

This would let you feel the button positions so you could reliably operate the calculator app without looking at the keys.

A fancier way would be for the case to actually have physical buttons on the case. The buttons are placed so they are over the on-screen buttons, but not touching them. When you press one of the case buttons it would touch the corresponding on-screen button. The buttons could have conductive material in them that connects from the top of the button to a conducting layer on the bottom, so pressing the button registers as a touch.

Even fancier would be an active case. It too would includes buttons, but instead of actually pressing the on-screen buttons these buttons would be connected to the phone via Bluetooth. This would give a lot of flexibility, but would cost more and would require power.