Plus42 Equations, Preview Release

[Thomas Okken]

New update:

1. HEAD nn, when used with a string that was one character longer than the longest that can fit in a register in place (*), would corrupt the first few characters of the string. This happened because the old string would be freed before the new one was copied into the register, which isn't safe if the new string happens to be a substring of the old one, as is the case with HEAD.
This affects Free42 as well, and will be fixed in 3.0.11.
2. In the equation editor, the \(\pi\) key now inserts the \(\pi\) character in STD mode. In COMP mode, it still inserts PI.
Note that this is strictly a cosmetic issue, since \(\pi\) and PI are both recognized as the number \(\pi\), in both STD and COMP modes. But since the HP calculators with which COMP mode is supposed to be compatible don't have the \(\pi\) character, avoiding it makes sense for the sake of two-way compatibility.
3. Added \(\pi\) to the ALPHA menu, in the MATH submenu. This is so it can be entered into equations even in COMP mode.
4. The ▸ and ↵ characters didn't have appropriate small-chars versions for use in menus. Fixed.

(*) Strings are stored in the matrix array if they fit within the same space as a floating-point number, including one byte for the string length. In the binary version, this means that strings up to 7 characters can be stored in the array, and in the decimal version, strings up to 15 characters can be stored in the array. Longer strings are stored in memory that is allocated separately, outside of the array. Normally, this is transparent to the user.