Acron RPN announces v3.0 BETA

[Nigel (UK)]

Here's my first attempt (layout file attached; remove the ".txt" extension before use). It adds an extra row of keys above the numbers to give access to some of the new functions. The added keys are:

• x - a variable for use in the functions below;
• zero - finds the zero of a function of x;
• integ - integrates a function of x between specified limits;
• deriv - finds the numerical derivative of a function of x at a particular value of x;
• sigma - sums a function of x over a specified range.
  

For example, to find a zero of \(\tan(x)-\sqrt{x}\):

• Enter this function onto the stack. Do this by pressing the "x" key, then "tan", then "x", then "\(\sqrt{}\)", then "-" (minus). Note that the default value stored in x is zero.
• Press "x" again; this tells the calculator which variable to solve for.
• Enter a starting value for x: 1, for example.
• Then press the "zero" key.
  

The answer appears in the stack.

The other functions work in a similar way, with the stack arguments being function, variable ("x" here, since I haven't put any others on the keyboard), and then one (zero, deriv) or two (integ, sigma) numerical values. These functions (and others) are described in the "Layout Documentation" linked to earlier in this thread.

I have many "classic" calculator apps on my phone and I enjoy using them all, but none of them are as convenient to use as AcronRPN when doing longer calculations. If you haven't seen it yet you really should give it a go. If RPN has a future, this is it!

Nigel (UK)