Note for subscribers: if you are interested in my Ada programming articles only, you can use this RSS feed link.

LEA, the Lightweight Editor for Ada, is based on the Scintilla text editor widget, which excels at colouring syntactic elements and letting the user rework his or her programs very swiftly, including manipulating rectangular selections and adding text on multiple points (usually vertically aligned).
But until recently, the cool features were limited to automatic indentation, adding comment delimiters (--) at the right column, or highlighting portions of text that match a selection.
Users were frustrated by not finding in LEA programming helpers (commonly grouped under the term "smart editor" or "intellisense") that they enjoy in their programming "studios".
An excuse would have been to dismiss such features as out of the scope of a "lightweight" editor.
But we know we can make of LEA a powerful mini-studio, with the ease of use of a simple editor, thanks to its "projectless" mode and the integrated HAC compiler.
So now, it happened.
From revision 385 of LEA (and revision 886 of HAC), you have now a good sense of intellisense:

• mouse-hover tips: when you let the mouse pointer on an identifier for a little while, a tip appears about that identifier (typically, where it was declared)
• context menu with a go-to-declaration entry, when applicable
  
• call tips: on typing '(' after a subprogram name, a tip appears with the subprogram's parameters
• auto-complete: on typing characters that belong to identifiers, a list of possible declared identifier appears; that list depends on where in the source code the text cursor is: declarations below the cursor are invisible and local declarations, possibly within multiple nested subprograms. 

Some screenshots will help illustrate the above points. Let's start with the sudoku_sample.adb example shipped with the HAC project. What's that "Sudo_Strings" type, for instance?
Just let the mouse pointer hang out around an occurrence of that keyword.

Mouse hover tip - Click image to enlarge it

Go to declaration - Click image to enlarge it

Declaration in the Sudoku package - Click image to enlarge it

Call tip - Click image to enlarge it

Auto-complete - Click image to enlarge it

• Currently, LEA only supports the HAC subset - it was the first priority. GNAT and other Ada compilers have their own editors and navigation features, so there is a lesser pressure to support them in LEA.
• The "smart editor" features are quite new and still under test and development. If you want to have them, you need to build LEA on a fresh clone (instructions are given in lea.gpr), then set (via regedit) the registry key SMART_EDITOR, in the branch HKEY_CURRENT_USER\SOFTWARE\LEA\, to "true", before starting LEA.
• You will notice a few missing things, like a list of fields on typing '.' after a record variable. They are not forgotten and just still "under construction".
• The "smart editor" features work on incomplete Ada sources. They might be just less present after the point of an error, especially a syntax error.

In order to develop the last point, here are a few examples on how LEA understands your program "on the fly", while you are typing it:

Smart editor on an incomplete piece of code - Click image to enlarge it

Smart editor on an incomplete piece of code, sample 2 - Click image to enlarge it

Smart editor on an incomplete piece of code, sample 3 - Click image to enlarge it

Some Web links:

LEA

Web site: http://l-e-a.sf.net/
Sources, site #1: https://sf.net/p/l-e-a/code/HEAD/tree/
Sources, site #2: https://github.com/zertovitch/lea
Alire Crate: Alire - LEA

Web site: https://hacadacompiler.sourceforge.io/
Sources, site #1: https://sf.net/p/hacadacompiler/code/HEAD/tree/
Sources, site #2: https://github.com/zertovitch/hac
Alire Crate: Alire - HAC

Enjoy!

Note for subscribers: if you are interested in my Ada programming articles only, you can use this RSS feed link.

Spot the "tool tip" on the following screenshot...

Click to enlarge

Translation: cross-references and source code navigation in LEA are becoming a reality since this evening!

Some Web links:

LEA

Web site: http://l-e-a.sf.net/
Sources, site #1: https://sf.net/p/l-e-a/code/HEAD/tree/
Sources, site #2: https://github.com/zertovitch/lea
Alire Crate: Alire - LEA

Since LEA embeds the HAC compiler, here are a few links about HAC as well:

HAC

Web site: https://hacadacompiler.sourceforge.io/
Sources, site #1: https://sf.net/p/hacadacompiler/code/HEAD/tree/
Sources, site #2: https://github.com/zertovitch/hac
Alire Crate: Alire - HAC

HAC (the HAC Ada Compiler) was since the first of its previous lives, from Pascal-S, in 1973, to recent commits, translating high-level language exclusively to the machine code of a fictitious machine (a Virtual Machine, abbreviated VM).

For writing a tiny compiler, a VM is very convenient:

• You (the compiler creator) can model and adapt it to your needs.
• You don't depend on hardware.
• You don't need to rewrite the code generation for each new hardware.
• You can make the VM running on many hardwares (hence the success of the JVM and .NET around year 2000).

The HAC VM and its users are enjoying all these advantages.

However, there is a flip side:

• A VM is much slower than a real machine (but till year 2000, it didn't matter; you could say: don't worry, just wait a few months for a more powerful computer).
• Since year 2000, the speed of microprocessors stopped doubling every six months (hence the declining interest in Virtual Machines). Despite the improvements in cache, RAM, and the multiplication of cores, the per-core performance improvement is slower and slower.
• Supporting only a VM gives the impression that your compiler can only compile to a VM.

Well, so far, the latter blame was objectively correct regarding HAC until a few weeks ago.
Now it is changing!
We have begun an abstract framework for emitting machine code.
With that framework, HAC can, on demand, emit code for its captive VM or for any implemented machine.
So you read well, it is not a just-in-time compiler translating VM instructions to native ones.
We are implementing a direct Ada-to-native compiler - and cross-compiler, since HAC doesn't know on which machine it is running!

The framework looks like this:

with HAC_Sys.Defs;

package HAC_Sys.Targets is

  type Machine is limited interface;

  type Abstract_Machine_Reference is access Machine'Class;

  --------------------
  --  Informations  --
  --------------------

  function Name (m : Machine) return String is abstract;
  function CPU (m : Machine) return String is abstract;
  function OS (m : Machine) return String is abstract;
  function Null_Terminated_String_Literals (m : Machine) return Boolean is abstract;

  ----------------------------
  --  Machine Instructions  --
  ----------------------------

  procedure Emit_Arithmetic_Binary_Instruction
    (m         : in out Machine;
     operator  :        Defs.Arithmetic_Binary_Operator;
     base_typ  :        Defs.Numeric_Typ) is abstract;

...

The code emission in the compiler is being changed (very slowly, be patient!) for going through this new abstract machine mechanism.
So far we have two implementations:

• The HAC VM - that way, we ensure HAC-for-HAC-VM works exactly as previously and can pass the test suite.
• A real target: the AMD64, running under Windows; the machine code is emitted in Assembler form, for the Flat Assembler (FASM).

The development for multiple targets is embryonic so far.
However, we can already compile a "hello world"-style program:

with HAT;

procedure Native is
  use HAT;
  a : Integer;
begin
  --  a := 1;  --  Variables: TBD.
  Put_Line ("Hello ...");
  Put_Line ("... world!");
  Put_Line (12340 + 5);
  Put_Line (12350 - 5);
  Put_Line (2469 * 5);
  Put_Line (61725 / 5);
end Native;

With the command:
hac -tamd64_windows_console_fasm native.adb

HAC produces this:

;  Assembler file for the Flat Assembler - https://flatassembler.net/

format PE64 console
entry _start
include 'include\win64a.inc'

section '.code' code readable executable

_start:
         push                9
         push                1
         push                -1
         push                -1
         pop                 r14
         pop                 r13
         pop                 r12
         pop                 r11
         add                 r12, _hac_strings_pool
         ccall               [printf], r12
         ccall               [printf], _hac_end_of_line
         push                10
         push                11
         push                -1
         push                -1
         pop                 r14
         pop                 r13
         pop                 r12
         pop                 r11
         add                 r12, _hac_strings_pool
         ccall               [printf], r12
         ccall               [printf], _hac_end_of_line
         push                12340
         push                5
         pop                 r11
         pop                 rax
         add                 rax, r11
         push                rax
         push                20
         push                10
         push                -1
         pop                 r14
         pop                 r13
         pop                 r12
         pop                 r11
         ccall               [printf], _hac_decimal_format, r11
         ccall               [printf], _hac_end_of_line
         push                12350
         push                5
         pop                 r11
         pop                 rax
         sub                 rax, r11
         push                rax
         push                20
         push                10
         push                -1
         pop                 r14
         pop                 r13
         pop                 r12
         pop                 r11
         ccall               [printf], _hac_decimal_format, r11
         ccall               [printf], _hac_end_of_line
         push                2469
         push                5
         pop                 r11
         pop                 rax
         imul                rax, r11
         push                rax
         push                20
         push                10
         push                -1
         pop                 r14
         pop                 r13
         pop                 r12
         pop                 r11
         ccall               [printf], _hac_decimal_format, r11
         ccall               [printf], _hac_end_of_line
         push                61725
         push                5
         pop                 r11
         pop                 rax
         xor                 rdx, rdx
         idiv                r11
         push                rax
         push                20
         push                10
         push                -1
         pop                 r14
         pop                 r13
         pop                 r12
         pop                 r11
         ccall               [printf], _hac_decimal_format, r11
         ccall               [printf], _hac_end_of_line
         stdcall             [ExitProcess],0

section '.data' data readable writeable
_hac_end_of_line  db 10, 0
_hac_decimal_format  db "%d", 0
_hac_strings_pool db "XHello ...", \
    0, "... world!", 0

section '.idata' import data readable
library kernel,'kernel32.dll',\
        msvcrt,'msvcrt.dll'
import  kernel,\
        ExitProcess,'ExitProcess'
import  msvcrt,\
        printf,'printf'

As you can see, the assembler code needs badly some simplification, but, anyway: it works.
FASM produces from it a relatively small 2048-byte executable which writes

Hello ...
... world!
12345
12345
12345
12345

The executable is full of zeroes, due to alignments. The non-zero bytes (more or less, the actual machine code and data) take 605 bytes.

Some Web links for HAC:

Main URL: https://hacadacompiler.sourceforge.io/
Sources, site #1: HAC Ada Compiler download | SourceForge.net
Sources, site #2: GitHub - zertovitch/hac: HAC Ada Compiler - a small, quick Ada compiler fully in Ada
Alire Crate: Alire - Hac

These are not really quines, but funny self-references around computer programs...

1) LEA:

Click to enlarge image

2) HAC:
 

Click to enlarge image

Main URL: https://hacadacompiler.sourceforge.io/
Sources, site #1: HAC Ada Compiler download | SourceForge.net
Sources, site #2: GitHub - zertovitch/hac: HAC Ada Compiler - a small, quick Ada compiler fully in Ada
Alire Crate: Alire - Hac

What’s new:

• You can use a loop’s name for the exit statement: exit Loop_Name.
• You can exit multiple, nested, loops, by using exit Loop_Name.
• Ada semantics are better verified:
  • Array indexing (i)(j) (array of array) and (i, j) (multi-dimensional array) are no more treated as equivalent (this feature was a remnant of the Pascal syntax).
  • Separation between Type and Subtype declarations (anonymous types are allowed only in the few cases foreseen by the language).
  • Operators of the HAT package (+, -, & for strings) are visible without prefix only in the scope of a use HAT clause.

Note that correct Ada programs, in relation to the above points, were already accepted and parsed correctly by HAC before that change.

Finally, a bit of cosmetics in the build messages:

C:\Ada\hac\exm>..\hac -v2 -c pkg_demo.adb

*******[ HAC ]*******   HAC is free and open-source. Type "hac" for license.
       [ HAC ]          HAC Ada Compiler version 0.26, 08-Jul-2023
       [ HAC ]          Compiling main: pkg_demo.adb
       [ HAC ]          | Compiling x_pkg_demo_s.ads (specification)
       [ HAC ]           \ Compiling x_pkg_demo_s1.ads (specification)
       [ HAC ]            \ Compiling x_pkg_demo_s11.ads (specification)
       [ HAC ]            /           x_pkg_demo_s11.ads: done.
       [ HAC ]            \ Compiling x_pkg_demo_s12.ads (specification)
       [ HAC ]            /           x_pkg_demo_s12.ads: done.
       [ HAC ]            \ Compiling x_pkg_demo_s13.ads (specification)
       [ HAC ]            /           x_pkg_demo_s13.ads: done.
       [ HAC ]           /           x_pkg_demo_s1.ads: done.
       [ HAC ]           \ Compiling x_pkg_demo_s2.ads (specification)
       [ HAC ]            \ Compiling x_pkg_demo_s21.ads (specification)
       [ HAC ]            /           x_pkg_demo_s21.ads: done.
       [ HAC ]            \ Compiling x_pkg_demo_s22.ads (specification)
       [ HAC ]            /           x_pkg_demo_s22.ads: done.
       [ HAC ]            \ Compiling x_pkg_demo_s23.ads (specification)
       [ HAC ]            /           x_pkg_demo_s23.ads: done.
       [ HAC ]           /           x_pkg_demo_s2.ads: done.
       [ HAC ]           \ Compiling x_pkg_demo_s3.ads (specification)
       [ HAC ]            \ Compiling x_pkg_demo_s31.ads (specification)
       [ HAC ]            /           x_pkg_demo_s31.ads: done.
       [ HAC ]            \ Compiling x_pkg_demo_s32.ads (specification)
       [ HAC ]            /           x_pkg_demo_s32.ads: done.
       [ HAC ]            \ Compiling x_pkg_demo_s33.ads (specification)
       [ HAC ]            /           x_pkg_demo_s33.ads: done.
       [ HAC ]           /           x_pkg_demo_s3.ads: done.
       [ HAC ]          |           x_pkg_demo_s.ads: done.
       [ HAC ]          | Compiling x_pkg_demo_m.ads (specification)
       [ HAC ]          |           x_pkg_demo_m.ads: done.
       [ HAC ]          | Compiling x_pkg_demo_b.ads (specification)
       [ HAC ]          |           x_pkg_demo_b.ads: done.
       [ HAC ]          Compilation of pkg_demo.adb (main) completed
       [ HAC ]          ------  Compilation of eventual with'ed unit's bodies
       [ HAC ]          | Compiling x_pkg_demo_s.adb (body)
       [ HAC ]          |           x_pkg_demo_s.adb: done.
       [ HAC ]          | Compiling x_pkg_demo_s1.adb (body)

Note for subscribers: if you are interested in my Ada programming articles only, you can use this RSS feed link.

Just as a teaser for the next Advent of Code in 10 1/2 months, we would like to show a few pictures related to last edition. The 25 puzzles, data and solutions can be found here and here. They are programmed with HAC (the HAC Ada Compiler), thus in a small subset of the Ada language. The HAC compiler is very fast, so you run your program without noticing it was ever compiled, which is perfect for completing a programming puzzle.

Day 22 run with HAC (here, embedded in the LEA environment)

However, the program will run substantially slower than compiled with a native, optimizing compiler like GNAT.
This is not an issue for most Advent of Code puzzles, but for some, it is, especially on the later days. Fortunately, changing from HAC to GNAT is trivial (just switch compilers), unlike the traditional reprogramming of Python prototypes in C++, for instance.

The pictures

Day 8's data is a map representing the height of trees. Once the puzzle was solved, I was curious how the forest looked like. Note that different users get different data, so you are unlikely to find a visualisation of exactly your data on the internet.

Day 12's puzzle is a shortest path problem with specific rules and a nice data - a terrain with a hill - which seems designed to trap depth-first-search algorithms into an almost infinite search. The yellowish path is the shortest from the green dot, elevation 'a', to blue dot, elevation 'z'.
The pinkish path is the shortest from the blue dot to any dot with elevation 'a'. Fortunately Dijkstra's algorithm (and perhaps others) allows for such a special criterion regarding the end point.

Click to enlarge

For day 22’s puzzle, a walk on a cube’s surface is involved, so it is helpful to sketch it on a piece of paper, cut it and glue the faces. A banana skin of that puzzle is that the example’s layout may be different from the data’s layout. We slipped on that one and ended up gluing and programming the face-to-face transitions for two layouts…

Click to enlarge

Other Adaists’ solutions, discussions and pictures can be found here and in the "2022 Day x" threads in the same forum.

The 0.85 version of LEA (the Lightweight Editor for Ada) is available!

Web site: http://l-e-a.sf.net/
Source repository #1: https://sf.net/p/l-e-a/code/HEAD/tree/
Source repository #2: https://github.com/zertovitch/lea

The new version has two main new features:
  - Tabs (screenshot below)
  - LEA doesn't write scilexer.dll as a file; thus, it runs as a portable application (in the sense: you can run it from a read-only drive directly, without installation)

Click to enlarge

Enjoy!

Note for subscribers: if you are interested in my Ada programming articles only, you can use this RSS feed link.

The 0.84 version of LEA (the Lightweight Editor for Ada) is available!

Web site: http://l-e-a.sf.net/
Source repository #1: https://sf.net/p/l-e-a/code/HEAD/tree/
Source repository #2: https://github.com/zertovitch/lea

This version is essentialy a rework of LEA's ergonomy - we had recently the chance of having a group of young first-time programmers and first-time LEA users to test it!

The main addition is the green Build & Run button, which matches a (less intuitive) menu entry and the F9 key.

Click screenshot to enlarge

Another addition is a dedicated box for the "User_Abort" internal Virtual Machine exception, so that the LEA user doesn't take the exception message for an actual error (which would be the case for any other exception).

Before:

Now:

Here is an example to illustrate how the HAC compiler is embedded in an Ada application.

The user of the application has typically only an executable (built with a "full Ada" system like GNAT) and an "Ada-pplet" (can be a few lines) that is run from that executable.

Normally, applications have different languages for building the application and for the embedded script system: Excel is written in C/C++ but embeds VBA (Visual Basic for Applications). 3D Studio Max has MaxScript. GIMP uses Script-fu, a variant of Scheme. Others use Lua or Python. Of course nobody would think about shipping a software with a scripting language where you have to fight with pointers and conditional compilation (C/C++).

But... how about an application that is written in a compiled language, but is using the same language for its scripting purposes? Since a few days, it is possible with HAC (the HAC Ada Compiler).

If you build the demo exchange_hac_side.adb (e.g. from GNAT Studio, or via the command "gprbuild hac"), you get an executable, exchange_hac_side on Linux or exchange_hac_side.exe on Windows. If you run it, you get:

Messages as "Native" are from the main application.

Messages as "HAC" are from the small HAC program that is run from the application.

A little disadvantage of having the same language on both sides... is that it is the same language! It could be confusing at first glance. Plus, it is not in the tradition. That may be disturbing for a number of people.

A big advantage of having the same language is that you can share some pieces of code. For instance the following package is used for building the demo application, and compiled by HAC when the application is running!

HAC (HAC Ada Compiler) is a quick, small, open-source Ada
compiler, covering a subset of the Ada language.
HAC is itself fully programmed in Ada.

Web site: http://hacadacompiler.sf.net/
From there, links to sources, and an executable for Windows.

Source repositories:
  #1 svn: https://sf.net/p/hacadacompiler/code/HEAD/tree/trunk/
  #2 git: https://github.com/zertovitch/hac

* Main improvements since v.0.1:

  - a program run by HAC can exchange data with the
      programm running HAC, through dynamically registered call-backs
      - see package HAC_Sys.Interfacing and demos:
        src/apps/exchange_native_side.adb
        src/apps/exchange_hac_side.adb

  - the compiler checks that all choices in a CASE statement
      are covered

  - the compiler performs more compile-time range checks and
      optimizes away useless run-time checks when it's safe to do so.

Enjoy!

Gautier

In order to illustrate a feature, what is better than a visual example?
In our case, the feature is the modularity, recently implemented in HAC (the HAC Ada Compiler).
So, a nice exercise was to try with a "real" visual package, PDF_Out (project Ada PDF Writer, link here).
Of course, HAC is still a small compiler project which doesn't cover all the sexy features of Ada - even those of the first version of Ada, Ada 1983, which already had extensive generics, aggregates (on-the-fly composite objects as expressions), default values in records or in subprogram parameters, exceptions or user-defined operators.
The easy way of down-stripping PDF_Out for HAC was to open the source code in the LEA editor (link here), and do frenetically and iteratively:

loop
  punch the compile key (F4)
  exit when the package compiles!
  make the code HAC-compatible (sometimes, it hurts!)
end loop

A few things that needed a downgrade for the HAC 0.1 language subset were:

• Object-oriented type extension (tagged type for PDF stream). In the simplified version, PDF files are the only supported PDF streams.
• Object.method notation
• Default values in records, replaced by explicit initialization.
• Inclusion of raster images (NB: the removal of that feature was unnecessary).
• User-defined exceptions (PDF_stream_not_created, ...).
• User-defined operators ("+", ...).
• Indefinite page table and offset table.

The result can be seen here:

Click to enlarge

You can experiment it yourself by checking out or cloning the latest version of HAC:

#1 svn: https://sf.net/p/hacadacompiler/code/HEAD/tree/trunk/
#2 git: https://github.com/zertovitch/hac

The new PDF examples are located in the subdirectory ./exm/pdf

Drum rolls: HAC (the HAC Ada Compiler) now supports packages.

OK, there is still a slight limitation: library-level packages cannot contain variables and constants, nor an initialization part (begin .. end). Removing this limitation would be complex to implement and is postponed so far for HAC.

A new modularity demo can be found in the "exm" subdirectory.
The main file is "pkg_demo.adb".
It is a simple test for simulating the build of an application with numerous dependencies.
The dependencies take form of packages depending on two or more other packages, down to
a certain recursion depth.
Each package contains a procedure with the same name: "Do_it", which just writes a string related to the package name. For instance,  X_Pkg_Demo_B3.Do_it will write "[B3]", then call X_Pkg_Demo_B31.Do_it, X_Pkg_Demo_B32.Do_it, and X_Pkg_Demo_B33.Do_it.
The package dependencies can be seen the following chart:

NB: the depth and number of children can be set as you wish.

How to run the demo?
First, we generate the package tree.
For that, assume you have the "hac[.exe]" executable ready in the main directory.
Note: in what follows, replace '/' by '\' if you are on Windows.
In the "exm" directory, run from the command line: "../hac pkg_demo_gen.adb".
Alternatively, from LEA, load "pkg_demo_gen.adb" and run it (F9).
The packages ("x_*" files) will be generated.

Now, from the command line, run "../hac pkg_demo.adb" (or from LEA, load it and punch F9).

The result is:

     Specs:  [S][S1][S11][S12][S13][S2][S21][S22][S23][S3][S31][S32][S33]    
     Mixed:  [M][M1][M11][M12][M13][M2][M21][M22][M23][M3][M31][M32][M33]    
     Bodies: [B][B1][B11][B12][B13][B2][B21][B22][B23][B3][B31][B32][B33]    
    
If you are curious about how HAC does the whole build the 40 units (main procedure and 39 packages),
add the "-v2" option to the build command: "../hac -v2 pkg_demo.adb".
On an i7 machine (with HAC itself built in "Fast" mode), the time elapsed
for the entire build is around 0.08 seconds. Only one core is used.
Since GNAT builds also the library "on the fly" by automatically
finding dependencies, you can see it in action by doing:
"gnatmake -I../src -j0 pkg_demo"
Interestingly, GNAT compiles the packages for each depth successively.
Then you can see the result by doing:
"./pkg_demo"
Of course, it's identical to HAC's. 

---

HAC (the HAC Ada Compiler) is a small, quick, open-source Ada compiler,
covering a subset of the Ada language.
HAC is itself fully programmed in Ada.

Web site: http://hacadacompiler.sf.net/

Source repositories:
#1 svn: https://sf.net/p/hacadacompiler/code/HEAD/tree/trunk/
#2 git: https://github.com/zertovitch/hac
 

Enjoy!

Gautier

Since a few commits, HAC parses packages! But so far there are limitations : it's "work in progress".

Nevertheless you can already play a bit with the things already programmed in HAC.

File prc.ads:

with Pkg_1, Pkg_2;

procedure Prc is
  x : Pkg_1.A;
 
  use Pkg_1, Pkg_2;

  xg : G;
  y : B;
  z : Pkg_1.E;

begin
  x := 0;
  y := 0;
  z := 2;
end;

File pkg_1.ads:

HAC (HAC Ada Compiler) is a small, quick, open-source Ada compiler,
covering a subset of the Ada language.
HAC is itself fully programmed in Ada.

Web site: http://hacadacompiler.sf.net/

Source repositories:
#1 svn: https://sf.net/p/hacadacompiler/code/HEAD/tree/trunk/
#2 git: https://github.com/zertovitch/hac

Main improvements since v.0.095:

• range checks on discrete subtype assignment (:=) and conversion
• short-circuit logical operators: "and then", "or else"
• for S = Scalar subtype: S'First, S'Last, S'Succ, S'Pred, S'Pos, S'Val, S'Image, S'Value, S'Range attributes
• for A = array object or array subtype: A'First [(N)], A'Last [(N)], A'Range [(N)], A'Length [(N)] attributes
• "&", "<", ">", "=", "/=" operators defined for the String type (additionally to HAL.VString type)
• CASE choices admit ranges
• forward declarations for subprograms

Enjoy!

Gautier

PS: for Windows there is an integrated editor that embeds HAC:
LEA: http://l-e-a.sf.net

 Time for the family to celebrate... and to recover from the advent puzzles epidemic 😉

• Advent of Code - with solutions done with HAC
  
• Mathe im Advent
• MATH+ Adventskalender
• EXIT - Das Spiel: Adventskalender

First of December: first door of the Advent calendar!

For some nerds it takes the form of the Advent of Code 😎.

For us, the game is also an opportunity to enrich the examples collection of HAC (the HAC Ada Compiler).

My solutions are available here and here.

Up to a few hours ago, range checks in HAC (the HAC Ada Compiler) were limited to array indices.

However, a simple and cool Ada feature is the possibility of subtyping, as in

subtype Level is Integer range 1 .. 30;

switch : array (Level) of Boolean;

or 

for x in Level loop ...

Furthermore it opens the possibility of checking that values are actually within the range.

Typically you have at some places a statement like:

lev := lev - 1;

for a variable defined as

lev : Level;

Up to a few hours ago, HAC did not have that kind of range check. Now it is fixed.

Since types in the HAC Ada subset are fully known at compile time, the addition was actually easy:

1) Add appropriate Virtual Machine instructions:

2) Implement them in the VM interpreter:

3) On the parser side, add the run-time check for (sub)type conversions (better to do an easy case as a warm-up):

4) Add the run-time check for assignment statements (:=):

For instance, for a composite type like

type Rec is record

  L : Level;

  Points : Natural;

end record;

and an array

x : array (1 .. N) of Rec;

the compiler needs to track correctly that

x(i).L

is of subtype Level, with the range 1 .. 30, and not only of the broader type Integer, when it considers checking the range of the value after := in the following statement:

x(i).L := new_value;

Conversely, in an expression like  z + y * x(i).L, the subtype has to be ignored, it is an Integer expression and nothing more (Integer in that case is called the base type). A solution was to define, in the compiler, a type extension for holding subtype informations:

In places where the subtype constraint needs to be ignored, it is easy to do: