Release 0.8.0 "Gabriel" - Symbolic operations, equations and library

This release adds symbolic integration, differentiation and equation
solving, delivers an extensive equation library, and improves the
library feature to enable large library objects to be defined in
separate files and optimize execution speed for library items.
It also improves the rendering of complex equations and fixes a number
of crashes or user-interface problems.

**Features**

* Symbolic integration, `Primitive` command, `'∫X(sin(X))'` syntax
  `'∫X(sin(2*X+3)-X)'` evaluates as `'-cos(2*X+3)/2-x²/2'`
* Symbolic differentiation, `Derivative` command, `∂X(sin(X))` syntax
  `'∂X(sin(2*X+3)-X)'` evaluates as `'2·cos(2*X+3)-1'`
* Symbolic equation resolution, `ISOL` (`Isolate`) command
  '`sin(2*X+3)=A' 'X' ISOL` gives `'X=(sin⁻¹ A+2*i1*π-3)/2'`
* Apply arithmetic and functions on both sides of equations like `A=B`
  `'A=B' sin 1 +` results in `'sin A+1=sin B+1'`
* Add possibility to define library objects in separate files
  The various demos from previous releases are now also in the library
* commands: Add `→Prog` command to convert expressions to RPL programs
  `'sin(2*X-Y)' →Prog` gives `« 2 X × Y - sin »`
* Accelerate evaluation of library entries
  Invoking a library object is as fast as if it was on the stack.
  Notice that this is faster than global objects that require lookup.
* Add ``Obj→` support for user-defined function calls
  `'F(A;B;C)' Obj→ DROP Obj→ ` gives `[F A B C]`.
  The first call to `Obj→` expands the expression, leaving an isolated
  function call on the stack, which the second `Obj→` expands.
* Automatically convert polynomial objects to expressions when needed
* Many improvements to the equation library contributed by Jean Wilson
* Document the equation library variables in the help file
* Add classical/relativistic Kinetic Energy comparison demo
  This was suggested by Jean Wilson as an illustration
* parser: Parse and convert HP syntax for `|`
  Typing `'A(X;Y)|(X=1;Y=2)'` converts to `'A(X;Y)|X=1|Y=2'`

**Bug fixes**

* Improve graphical rendering of some complex expressions
* Render `sqrt` as `√` and not `squareroot` in HP compatibility mode
* Do not draw parentheses around `|x|` when rendering `abs`
* Redefine `rpm` as `turn/min` (unit consistency of rotational speed)
* Avoid crash in `for` loop if termination condition fails to evaluate
* Fix rendering and saving of directories
* Do not leave incorrect stack content when running `Obj→` on text
* Make size consistent in vectors containing tagged objects
* Accept tagged objects as input in algebraic functions
* Avoid parsing error for `1,234` when `.` is the decimal separator
* Debug output related to expressions is no longer labelled "equations"
* Fix unit error in Drift Speed & Current Density
* Cut the size of the build version ID to avoid DMCP buffer overflows
* Avoid possible corruption when an error occurs in a program
* Improve error messages for file errors, e.g. when loading a state
* Move cursor at correct position after numbers when entering units
* Reject multiple consecutive units, e.g. `1_m_s`
* Fix issue where we insert `=` incorrectly on the command line
* Address simulator warning about potential buffer overflow

**Improvements**

* tests: Add tests for the newly added library entries
* primitive: Add test suite for symbolic integration
* tests: Add test suite for symbolic differentiation
* Factor out code to expand objects on the stack
* `make install` now Installs from distribution files
* demo: Reorganize demo files as directories
* tests: Add test for `Obj→` on various object types
* tests: Factor out code checking state of the complete stack
* tests: Avoid emitting something that looks like compilation errors
* Update demo file
* Improve definition of atomic mass unit, add `Da` (Dalton) alias
* expressions: Optimize the way to split an equation
* tests: Adjust tests after changes in `SymbolicMenu`

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

Release 0.7.18 "Who" - Subst, Where, Apply

This release implements the `Apply`, `Subst` and `|` (`Where`) commands.

**Features**

* ui: Allow Shift-SPC to enter `=` in an expression
* Implement `subst` and `where`
* Implement the `Apply` command
* Implement the `EQNLIB` command
* Add `CONSTANTS` as a way to select mathematical constants menu
* Add `CONLIB` as an alias for `ConstantsMenu`.

**Bug fixes**

* solver: Adjust detection of "epsilon" for large values
* ttf2font: Flip x coordinates for dense fonts

**Improvements**

* doc: List commands that will never be implemented

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

Release 0.7.17 "Open" - DoSubs, DoList, entering units

This release adds `DoSubs`, `DoList`, `NSub` and `EndSub` commands, and fixes
related issues that were found with the associated examples in teh HP50G
Advanced Reference Manual.

**Features**

* lists: Implement `DoList`, `DoSubs`, `NSub` and `EndSub`
* units: Add usual "big" units to `Computing` units menu (e.g. KB, MB)
* graphics: Add `Freeze` command
* ui: Make it easier to enter units
* expressions: Accept algebraic forms for `integrate` and `root`
* expressions: Graphical rendering of integrals

**Bug fixes**

* case: Preserve the code for the default case (which was lost before)
* parser: Parse arg-less alegbraic commmands such as `NSub`
* equations: Fix syntax errors in built-in equations, e.g. missing parentheses
* equations: Replace variables that match DB48X command names, e.g. `Re`
* equations: Replace imperial units with SI units, e.g. `in` with `cm`
* units: Reject user-defined functions in unit expressions
* constants: Fix definition for the `qε0` constant

**Improvements**

* Update help about equations with some additional material
* tests: Run through all the builtin equations
* ui: Do not insert an extra space before parentheses in equation
* simulator: Add macOS icons for DB48X and DB50X
* font: Record saved font with `v` update

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

Release 0.7.16 "Clean" - New commands

The focus of this release is on new commands, notably for matrix and vector
operations. This release also ships with a DM48X-specific keymap, which fixes a
problem with teh file selector on the DM32. The equation library has been extended with numerous equations, but they are not fully validated yet.

**Features**

* `con`, `idn` and `ranm` matrix generation commands
* `Array→` and `→Array` commands to convert array to/from stack
* `dot` product and `cross` product commands for vectors
* `DispXY` styled text rendering command
* `DupDup` command duplicating top item twice
* Add a large number of equations to equation library

**Bug fixes**

* Fix `decimal::to_bignum` for small magnitudes
* Return angle unit for `atan2` and `arg` commands
* The `for` loop on lists no longer ends leaving the debugger active
* Interactive stack `DropN` command returns to level 1
* Fix file selector's "New file" on DM32 so that ENTER terminates it
* A few fixes in equations in the equation library

**Improvements**

* Improve graphical rendering of expressions such as multiplication operators
* doc: Update status
* font: Fix `v` glyph vertical placement, add dot and cross glyphs
* ttf2font: Add additional verbose info about source data
* Add `CONSTANTS` as an alias for `ConstantsMenu`
* Replace documentation references to `EEX` with `×10ⁿ`
* Optimize parsing of real numbers in parentheses

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

ios: Release i0.7.16 "Clean" - New commands

The focus of this release is on new commands, notably for matrix and vector
operations. This release also ships with a DM48X-specific keymap, which fixes a
problem with teh file selector on the DM32. The equation library has been extended with numerous equations, but they are not fully validated yet.

**Features**

* `con`, `idn` and `ranm` matrix generation commands
* `Array→` and `→Array` commands to convert array to/from stack
* `dot` product and `cross` product commands for vectors
* `DispXY` styled text rendering command
* `DupDup` command duplicating top item twice
* Add a large number of equations to equation library

**Bug fixes**

* Fix `decimal::to_bignum` for small magnitudes
* Return angle unit for `atan2` and `arg` commands
* The `for` loop on lists no longer ends leaving the debugger active
* Interactive stack `DropN` command returns to level 1
* Fix file selector's "New file" on DM32 so that ENTER terminates it
* A few fixes in equations in the equation library

**Improvements**

* Improve graphical rendering of expressions such as multiplication operators
* doc: Update status
* font: Fix `v` glyph vertical placement, add dot and cross glyphs
* ttf2font: Add additional verbose info about source data
* Add `CONSTANTS` as an alias for `ConstantsMenu`
* Replace documentation references to `EEX` with `×10ⁿ`
* Optimize parsing of real numbers in parentheses

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

Release 0.7.15 "Teaching" - Bug fixes notably on iOS

This release mostly focuses on issues exposed by the iOS releases.
It's a bug-fixes only release.

***Bug fixes***

* ios: Fix a screen refresh bug delaying the display of computation results
* ios: Increase user-accesssible memory for DB50X to match the DM32
* files: Avoid opening two files when a loaded file contains units/constants
* units: Restrict unit expressions further, e.g. forbid `1_km^s`
* build: Do not add unwanted macOS-specific files in release tar files
* build: Remove irrelevant help file from releae tar file
* constants: Fix numerical value for G constant
* tests: Rename `M` demo helper to `D`, since we use `M` in symbolic tests
* makefile: Add `mv` echo to targets doing image comparison
* units: Use pi constant in definition of radians unit
* parser: Detect syntax error on `(inv(x))` in non-expression mode
* units: Avoid infinite loop for bad unit exponents
* files: Avoid crash in `file_closer` if file does not exist
* tests: Add DMS/HMS operations to math demo
* tests: Add keyboard shortcuts to launch the demos

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

Release i0.7.15 "Teaching" - Bug fixes notably on iOS

This release mostly focuses on issues exposed by the iOS releases.
It's a bug-fixes only release.

**Bug fixes**

* ios: Fix a screen refresh bug delaying the display of computation results
* ios: Increase user-accesssible memory for DB50X to match the DM32
* files: Avoid opening two files when a loaded file contains units/constants
* units: Restrict unit expressions further, e.g. forbid `1_km^s`
* build: Do not add unwanted macOS-specific files in release tar files
* build: Remove irrelevant help file from releae tar file
* constants: Fix numerical value for G constant
* tests: Rename `M` demo helper to `D`, since we use `M` in symbolic tests
* makefile: Add `mv` echo to targets doing image comparison
* units: Use pi constant in definition of radians unit
* parser: Detect syntax error on `(inv(x))` in non-expression mode
* units: Avoid infinite loop for bad unit exponents
* files: Avoid crash in `file_closer` if file does not exist
* tests: Add DMS/HMS operations to math demo
* tests: Add keyboard shortcuts to launch the demos

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>

ios version 0.7.14.

Release 0.7.14 "Kids" - Equation-related bug fixes

This release fixes a number of issues that were discovered primarily
through the Columns and Beams equations.

**Features**

* trigonometrics: Add conversion from non-standard angles, so that
  `cos(1_turn)` gives the correct result.
* debug: Debug on error with `DebugOnError` and `KillOnError`
  settings. This makes it easier to debug an RPL program, by making it
  possible to single-step around the instruction that generated the
  error.
* tests: Add three 30 second demo of DB48X features. These are to
  generate marketing videos for the iPhone version on the Apple
  store (to be done).

**Bug fixes**

* ui: Keep a GC pointer in `draw_object` to avoid a memory crash
* equations: Add missing units in some equations, e.g. `I` and `A` in
  second equation of Coilumns and Beams
* equations: Add explicit `radian` unit in Eccentric Columns `cos`,
  which ensures we get the correct result from the HP50G manual even
  when in Degrees mode.
* units: Correctly factor out non-integral powers, so that we can
  compute `1/sqrt(epsilon_0*mu_0)` and get the correct result.
* catalog: Display commands that begin with selection first, so that
  `FORE` shows `Foreground` before `AlphaForeground`.
* stats: When computing a sum, evaluate the expression on all
  terms. The result for `Variance` with single variables was wrong
  because the first term was computed incorrectly due to a misguided
  optimization.
* graphics: Error out in `RGBPattern` for negative input. The negative
  values were generating an error, but it was not reported, so the next
  command was likely to report it.
* help: Render shift keys correctly in the color version. The bitmap
  was interpreted as containing color data. Colorize it instead.

**Improvements**

* ui: Select orange as background color during search. The previous
  setting of showing seardch using white foreground on a white
  background was probably pushing the notion of "blind search" a bit
  too far.

Release 0.7.13 "Murderers" - Solver improvements

This releases focuses on improvements to the solver, with the completion of the
Columns and Beams section from the HP50G equation library.

**Features**

* equations: Add remaining equations from "Columns and Beams"
* loops: For loops on lists and arrays
* menus: Add `R→D`, `D→R`, `→Polar` and `→Rectangular`
* menus: Automatically select tools menu for library equations
* units: Allow `ubase` to work on expressions
* units: Graphic rendering of units

**Bug fixes**

* 48calc.org: Fix mouse click position
* `#ABC #DEF -` now correctly produces a based number with >64-bit wordsize
* conditionals: Parse and evaluate `IFTE` correctly
* equations: Fix Elastic Buckling
* files: Avoid crash in `file_closer` if file was not open
* istack: Enable Swap feature on top two levels
* menu: Update SolvingMenu when updating VariablesMenu
* parser: Deal with negation more "normally", parse `-a²` correctly
* solver: Compute units correctly for inputs
* solver: Do not change unit when storing in a solver variable
* solver: Emit correct error message in `EvalEq` if missing variables
* solver: Preserve errors reported by underlying function
* units: Do not evaluate/render units with names
* units: No longer read variables `m` and `s` while processing `1_m/s`
* units: Simplify units that convert to real numbers

**Improvements**

* Update .gitignore
* build: Add BMP files to the distribution
* complex: Optimize exit conditions for parentheses
* solver: Add test for equation library
* solver: Add tests for solving with units
* solver: Improve behaviour of `EvalEq`
* solver: Keep units and constants as-is in equation
* solver: Make precision relative to equation sides magnitude
* stack: Show vectors vertically by default
* ui: Do not persistently hide stack with current equation
* units: Keep power integral, i.e. avoid getting `1_m^2.0/s`
* units: Strip tags from unit conversion functions
* units: The `EvalEq` command should not evaluate dates
* wasm: Add logos to the repository

Signed-off-by: Christophe de Dinechin <christophe@dinechin.org>