Creating New System Functions

Tuesday 3 December 2024 17:46 UTC NARS2000 Creating New Quad System Functions

Who Should Be Reading This Page

If you are an APL'er, an APL programmer or APL developer - this page may not be right for you. This page is for Developers who want to implement a new Quad or ⎕ command using the C/C++ language in NARS source code. Given that NARS source code is over a quarter million lines of highly evolved source code, it is helpful to have several starting points to work from, whether you are a gifted C++/C programmer, PHP programmer, Bison programmer or a relative newcomer to NARS source code. The basic premise is that you have an idea for a new Quad system function command for APL/NARS and wish to implement it, add it to NARS functionality. This page is a starting conceptual and reference point.

Helpful Starting Point Perspectives

Visually scan or browse the Build notes found in the ReleaseNotes subfolder, normally located in C:\NARS2000\trunk\ReleaseNotes using a text or string scanner program such as Windows File Explorer with its Search text box. Multiple time-lapsed prior examples of adding system functions should appear in those previous Build notes. Search for the specific text string, "system function" and there should be a number of references found/listed. These references give an idea of which files frequently need to be modified, including much about what you will need to do. For example, file <sysvars.c> contains code locations where all system variables and functions hook into the system - a primary symbol tables reference, an interpreter-table-of-contents file. You will further need to define a new c file for your system function, e.g. <qf_cmd.c> or <qf_menus.c> or <qf_grfx.c> or a similar name. Defining any new file also requires some specific changes such as new entries in <compro.h>, <makefile.src>, and <makefile.inc>. You'll also need to change <NARS2000.vcxproj> which you can do through Visual Studios 20xx GUI or IDE(integrated developer's environment). Try to maintain a list of the various files you edit/change because if NARS subsequently moves to a new release and you need to synch with it, it is helpful to know which files you modified - to synch plus reinstate, to bring forward your local changes.

For example, in C:\NARS2000\trunk\ReleaseNotes\Notes-1295.txt system function Quad T or ⎕T was created and implemented, to return a Tick Count for time-sensitive APL subroutine stop-watch timing purposes. The following seven files were edited/affected by the addition of system function ⎕T into NARS2000.exe. Listed below are edited notations extracted from <Notes-1295.txt>:

COMPRO.H:   #1
  Include <qf_t.pro> in the list of prototype files.

MAKEFILE.INC:   #2
MAKEFILE.SRC:   #3
NARS2000.32.VCPROJ:   #4
NARS2000.64.VCPROJ:   #5
  Include <qf_t.c> in the list of source files.   #6

QF_T.C   #6(again)
  Implement []T.

SYSVARS.C:   #7
  Include []T in the list of niladic system functions.

Note above how filenames edited/changed were kept track of, including general notes on what was performed including the purpose of the revision/edit-change by the System Developer. This filename + purpose tracking along with associated note keeping is considered good programming, a best developer practice. Such detailed record-keeping makes program flow and source-code maintenance much easier to follow and subsequently revise as needed.

Continuing with the formation or genesis process re system function ⎕T example just above, viewing(using a standard text editor such as notepad.exe) file <qf_t.c> which is the central ⎕T function-defining c file, you will note that the mnemonic(see #General Reference Notes) for ⎕T is SysFnT_EM_YY. A File Explorer search for string SysFnT_EM_YY will bring up primarily two found-in files, <qf_t.c> and <sysvars.c>.

Therefore we may conclude or determine - that operational functionality for this particular system function ⎕T was contained in just two files. The other five affected files, and not to be ignored, were impacted for overall programming structural integrity, potential debugging/compilation, and NARS2000 overall modeling purposes. Not every System Function impacts or requires so few files, but ⎕T is a solid 'minimal impact elsewhere' System Function example.

<sysvars.c> Reference Table

All ⎕ System Variables and System Functions, per system reference table (7 column table) are listed/defined within file <sysvars.c>. Quad T's entry is extracted just below. The sysvars table helps APL's interpreter understand "how" to handle each quad system variable and function, how each is "supposed to operate"; thus helping the Interpreter identify syntax errors, valence errors, domain errors, etc.
⎕T's entry(within niladic system functions grouping) in table:

SysName	Valence	Var?	Std?	Exec Routine(name)	Sys_Vars	Descr
QUAD L"t"	0	FALSE	FALSE	SysFnT_EM_YY	0	High Resolution Time

Every APL/APL2 Quad System Variable and Quad System Function(niladic, monadic and dyadic) has an entry in the <sysvars.c> table. System function ⎕T, because it is niladic, has a zero valence; it is not a System Variable(False); it has a function mnemonic or calling name = SysFnT_EM_YY; it uses zero system variables.

Source Code Derived List of APL System Functions

Source Code List of NARS Quad ⎕ System Functions, per qf_*.c Files Derivative. Sys Fcn Ct=30. Snapshot as of Thu 7/2/15 10:03:25 AM:

QuadFcn c FileName		APL System Function	Mnemonic Exec Name	c FileSize	Function Type(sysvars.c)	Description(sysvars.c)
C:\NARS2000\trunk\qf_a.c
⎕A	SysFnA_EM_YY	3,151	Niladic	Alphabet
C:\NARS2000\trunk\qf_at.c
⎕AT	SysFnAT_EM_YY	44,356	Monadic or Dyadic	Attributes
C:\NARS2000\trunk\qf_av.c
⎕AV	SysFnAV_EM_YY	5,188	Niladic	Atomic Vector
C:\NARS2000\trunk\qf_cr.c
⎕CR	SysFnCR_EM_YY	33,687	Monadic or Dyadic	Canonical Representation
C:\NARS2000\trunk\qf_d.c
⎕D	SysFnD_EM_YY	3,149	Niladic	Digits
C:\NARS2000\trunk\qf_dl.c
⎕DL	SysFnDL_EM_YY	8,265	Monadic or Dyadic	Delay Execution
C:\NARS2000\trunk\qf_dr.c
⎕DR	SysFnDR_EM_YY	49,334	Monadic or Dyadic	Data Representation
C:\NARS2000\trunk\qf_ea.c
⎕EA	SysFnEA_EM_YY	9,565	Monadic or Dyadic	Execute Alternate
C:\NARS2000\trunk\qf_ec.c
⎕EC	SysFnEC_EM_YY	17,469	Monadic or Dyadic	Execute Controlled
C:\NARS2000\trunk\qf_em.c
⎕EM	SysFnEM_EM_YY	3,106	Niladic	Event Message
C:\NARS2000\trunk\qf_error.c
⎕ERROR	SysFnERROR_EM_YY	7,129	Monadic or Dyadic	Signal Error
C:\NARS2000\trunk\qf_es.c
⎕ES	SysFnES_EM_YY	18,322	Monadic or Dyadic	Event Simulate
C:\NARS2000\trunk\qf_et.c
⎕ET	SysFnET_EM_YY	6,645	Niladic	Event Type
C:\NARS2000\trunk\qf_ex.c
⎕EX	SysFnEX_EM_YY	23,537	Monadic or Dyadic	Expunge Names
C:\NARS2000\trunk\qf_fmt.c
⎕FMT	SysFnFMT_EM_YY	108,506	Monadic or Dyadic	Format
C:\NARS2000\trunk\qf_fx.c
⎕FX	SysFnFX_EM_YY	18,028	Monadic or Dyadic	Function Fix
C:\NARS2000\trunk\qf_lc.c
⎕LC	SysFnLC_EM_YY	5,679	Niladic	Line Counter
C:\NARS2000\trunk\qf_mf.c
⎕MF	SysFnMF_EM_YY	38,096	Monadic or Dyadic	Monitor Function
C:\NARS2000\trunk\qf_nc.c
⎕NC	SysFnNC_EM_YY	20,952	Monadic or Dyadic	Name Classification
C:\NARS2000\trunk\qf_nfns.c
⎕NFNS	SysFnNAPPEND_EM_YY	260,952	Monadic or Dyadic	Append Data To An Open Native File
C:\NARS2000\trunk\qf_nl.c
⎕NL	SysFnNL_EM_YY	17,698	Monadic or Dyadic	Name List
C:\NARS2000\trunk\qf_sysid.c
⎕SYSID	SysFnSYSID_EM_YY	4,826	Niladic	System Identifier
C:\NARS2000\trunk\qf_sysver.c
⎕SYSVER	SysFnSYSVER_EM_YY	8,556	Niladic	System Version
C:\NARS2000\trunk\qf_t.c
⎕T	SysFnT_EM_YY	3,542	Niladic	High Resolution Time
C:\NARS2000\trunk\qf_tc.c
⎕TC	SysFnTC_EM_YY	12,390	Niladic	Terminal Control Characters
C:\NARS2000\trunk\qf_tf.c
⎕TF	SysFnTF_EM_YY	53,263	Monadic or Dyadic	Transfer Form
C:\NARS2000\trunk\qf_ts.c
⎕TS	SysFnTS_EM_YY	5,165	Niladic	Time Stamp
C:\NARS2000\trunk\qf_ucs.c
⎕UCS	SysFnUCS_EM_YY	23,003	Monadic or Dyadic	Universal Character Set
C:\NARS2000\trunk\qf_vr.c
⎕VR	SysFnVR_EM_YY	5,624	Monadic or Dyadic	Vector Representation of a Function
C:\NARS2000\trunk\qf_wa.c
⎕WA	SysFnWA_EM_YY	3,367	Niladic	Workspace Available

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Magic Function C Header File vs APL - a Comparison

Extract from NARS file C:\NARS2000\trunk\mf_quadvr.h for System Function ⎕VR (C source code header file, just below):

//***************************************************************************
//  Magic function/operator for Monadic []VR
//
//  Monadic []VR -- Visual Representation
//
//  Return a visual representation of a user-defined function/operator
//***************************************************************************

static APLCHAR MonHeaderVR[] =
  L"Z←" MFON_MonVR L" R;L;⎕IO";

static APLCHAR MonLineVR1[] =  
  L"⎕IO←0 ⋄ Z←1 ##.⎕CR R";
  
static APLCHAR MonLineVR2[] =  
  L"→(0≠⍴Z)/L1 ⋄ Z←'' ⋄ →0";
  
static APLCHAR MonLineVR3[] =  
  L"L1:→(1=≡Z)/0";
  
static APLCHAR MonLineVR4[] =  
  L"L←'∇'∊0⊃Z";
  
static APLCHAR MonLineVR5[] =  
  L"Z←(∊((⊂[1]'LO<    ∇>P<[>Q<]>I6' ⎕FMT⍳⍴Z),¨Z),¨⎕TCNL),'    ∇'";
  
static APLCHAR MonLineVR6[] =  
  L"→L/0 ⋄ Z←Z,(' ',⍕2 ##.⎕AT R),' (UTC)'";

static LPAPLCHAR MonBodyVR[] =
{MonLineVR1,
 MonLineVR2,
 MonLineVR3,
 MonLineVR4,
 MonLineVR5,
 MonLineVR6,
};

MAGIC_FCNOPR MFO_MonVR =
{MonHeaderVR,
 MonBodyVR,
 countof (MonBodyVR),
};

⎕VR - APL monadic function named MFON_MonVR(just below):

      ⎕CR 'MFON_MonVR'
Z←MFON_MonVR R;L;⎕IO                                        
⎕IO←0 ⋄ Z←1 ##.⎕CR R                                        
→(0≠⍴Z)/L1 ⋄ Z←'' ⋄ →0                                      
L1:→(1=≡Z)/0                                                
L←'∇'∊0⊃Z                                                   
Z←(∊((⊂[1]'LO<    ∇>P<[>Q<]>I6' ⎕FMT⍳⍴Z),¨Z),¨⎕TCNL),'    ∇'
→L/0 ⋄ Z←Z,(' ',⍕2 ##.⎕AT R),' (UTC)'

Note the displaced lines yes, but great/identical similarity between the UTF-8 C source code header file and the actual APL function MFON_MonVR. In a very real sense, APL source code was imported directly into C source code via a header file, using a magic function. Hence the term magic since APL magically gets executed inside a compiled C program. This is somewhat code-wise equivalent to using the ⍎(execute) function in APL. Technically the APL simulation in C was made possible and accomplished via re-formatting the ⎕CR representation of an APL function, placing it into a C source code header file, and using PHP in the NARS2000 project model. Also technically, note the use of L" in the header file at the front of several lines - the presence of the prefix L in C source code indicates Unicode string to the C compiler.

Ref. also System Function ⎕VR and System Function ⎕CR

For Magic Functions: In addition to creating a header file such as mf_quadvr.h, magic function header files need reference via a caller file such as qf_vr.c. Also, referencing table entries are required in files execmfn.h and execmfn.c within the \trunk folder.

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General Reference Notes

Notation Convention on this wiki page: Unless otherwise specified all file names used on this page will exclude their path which is C:\NARS2000\trunk\.

Every programming language uses at least two primary concepts 1) mnemonics and 2) a syntax to implement that language. NARS is no different. Every NARS quad system command has an associated mnemonic or reference name. For example, Quad CR or ⎕ CR - Canononical Representation - uses mnemonic SysFnCR_EM_YY, as found in its definition file qf_cr.c. Quad FX or ⎕ FX - Fix or Function eXecute - uses mnemonic SysFnFX_EM_YY, per file qf_fx.c. Note the similarity in file naming conventions for both c files.

Several Quad functions have been implemented using PHP magic functions, for example Quad VR or ⎕ VR - Visual Representation - uses mnemonic SysFnVR_EM_YY, per definition file qf_vr.c. However, Quad VR also has an additional PHP magic header file called in this case mf_quadvr.h. Quad FMT is similarly coded using a PHP magic function header file.