(41) Alpha stack

[grsbanks]

I couldn't find the program I wrote originally so I basically rewrote it.

Text copy/pasted from my blog entry (http://techy.horwits.com/2018/12/alpha-s...p-41c.html)

NB: This program creates and manages a data file in Extended Memory called "ASTACK". If you already have a file of that name, it will be deleted! Note also that running these programs uses Flag 01 and trashes registers R07-R10. Finally, since this uses Extended Memory, you will need to run this on a 41CX or SwissMicros DM41, or on a 41C or 41CV with the "X-Function" module.

The size of the data file created in Extended Memory depends on the depth of the alpha stack that you want to create. Two registers are needed for a header in the file and four registers per stack level are needed. So, if you want a stack that's 6 levels deep, for example, then you'll need room in your Extended Memory for a file that's 2+6*4= 26 registers in size. You'll actually need 28 registers free because the calculator also steals 2 registers for its own internal housekeeping when you create a file in X-Mem.

The three utilities provided are "ASINIT", "APUSH" and "APOP".

ASINIT
Run this with the depth of the desired stack in X, The '41's own error detection will prevent you from creating a file that's too big or from running this on a machine with no "X-Function" module installed (remember, the 41CX and the DM41 have this module baked into their ROM).

APUSH
This will save the current contents of your alpha register onto the alpha stack and return 0 in X, unless the stack is already full, in which case you'll get -3 back instead. If the alpha stack hasn't been initialized (by running ASINIT) then you'll get -1 back in X.

APOP
This takes the string on the top of the alpha stack and transfers it into the '41's alpha register, removing it from the stack. If all went well, X will contain 0 after returning from this program. If the alpha stack has not yet been initialized then you'll get -1 back, or if the stack was already empty (everything already popped off it) when you called APOP then you'll get -2 back.

You can go and grab these utilities here: alpha-stack.zip

Software provided, as usual, as a text listing, a .raw file and a PDF with bar codes.