Plus42 Equations, Preview Release

[Thomas Okken]

New update:

1. Code execution no longer ends in generated code, at least when it runs without error. The integrator and the numerical solver already took care of restoring the current program position; the direct solver and EVAL now do, too.
2. Tentative implementation of run-time error reporting for equations: shows the part of the equation where an error occurred in the bottom line of the display. Note that this is rather crude; the main point of the exercise is to test the logic that translates program locations back to positions in the equation text, and see how well it works in practice. Ultimately, the goal is to open the offending equation in the equation editor with the cursor at the trouble spot, and print the equation with highlight in trace mode, etc.
3. Implemented the VARS option in the PRINT menu, for printing all the variables associated with the current equation.