The following program reads a grammar from the file
named c.def and print it on console. The grammar of grammar are used implicitly,
Formally, rules may be written in the same language, but how to use it?
Nonetheless here are the rules:
name ;
string ;
numb ;
colon ":" ;
or "|" ;
semi ";" ;
period "." .
Grammar : 0 Tokens period Rules period
;
Tokens : 0 Tokens semi Token
| 0 Token
;
Token : 0 name
| 0 name numb numb
| 0 name string numb numb
;
Rules : 0 Rules semi Rule
| 0 Rule
;
Rule : 0 Symbol colon Variants
;
Variants : 0 Variants or Variant
| 0 Variant
;
Variant : 0 numb Symbols
;
Symbols : 0 Symbols Symbol
| 0 Symbol
;
Symbol : 0 name
;
And the grammar loader program that read c.def file:
char Text [16384];
word pText;
word nText;
word nLine;
byte Code [16384];
word nCode;
word hFile;
char Heap [ 2048];
word nHeap;
word nData;
word Name [ 256];
word Cls [ 256];
word Sub [ 256];
word Type [ 256];
word Size [ 256];
word Ofs [ 256];
word nName;
word Sym [ 96];
word nSym;
word Left [ 128];
word Id [ 128];
word pRight [ 128];
word nLeft;
word Right [ 384];
word pLeft [ 384];
word nRight;
word Stk [ 32];
word nStk;
char Buff [ 32];
word open() is
inline 0xB4, 0x3D; // mov AH, 3DH
inline 0xB0, 0x00; // mov AL, 0
inline 0xBA, 0x4A, 0xC1; // mov DX, @@DATA+Ofs(Heap[64])
inline 0xCD, 0x21; // int 21H
end
word create() is
inline 0xB4, 0x3C; // mov AH, 3CH
inline 0xB9, 0x00, 0x00; // mov CX, 0
inline 0xBA, 0x4A, 0xC1; // mov DX, @@DATA+Ofs(Heap[64])
inline 0xCD, 0x21; // int 21H
end
word read() is
inline 0xB4, 0x3F; // mov AH, 3FH
inline 0x8B, 0x1E, 0x08, 0xC1; // mov BX, word [@@DATA+Ofs(hFile)]
inline 0xB9, 0x00, 0x40; // mov CX, 16384
inline 0xBA, 0x00, 0x41; // mov DX, @@DATA+Ofs(Text)
inline 0xCD, 0x21; // int 21H
end
word write() is
inline 0xB4, 0x40; // mov AH, 40H
inline 0x8B, 0x1E, 0x08, 0xC1; // mov BX, word [@@DATA+Ofs(hFile)]
inline 0x8B, 0x0E, 0x06, 0xC1; // mov CX, word [@@DATA+Ofs(nCode)]
inline 0xBA, 0x06, 0x81; // mov DX, @@DATA+Ofs(Code)
inline 0xCD, 0x21; // int 21H
end
word close() is
inline 0xB4, 0x3E; // mov AH, 3EH
inline 0x8B, 0x1E, 0x08, 0xC1; // mov BX, word [@@DATA+Ofs(hFile)]
inline 0xCD, 0x21; // int 21H
end
char putc(char C) is
char C1:=C;
inline 0x92; // xchg DX, AX
inline 0xB4, 0x02; // mov AH, 2
inline 0xCD, 0x21; // int 21H
end
word halt() is
inline 0xB8, 0x00, 0x4C; // mov AX, 4C00H
inline 0xCD, 0x21; // int 21H
end
word Init() is
Heap [ 0]:='0';
Heap [ 1]:='1';
Heap [ 2]:='2';
Heap [ 3]:='3';
Heap [ 4]:='4';
Heap [ 5]:='5';
Heap [ 6]:='6';
Heap [ 7]:='7';
Heap [ 8]:='8';
Heap [ 9]:='9';
Heap [ 10]:='A';
Heap [ 11]:='B';
Heap [ 12]:='C';
Heap [ 13]:='D';
Heap [ 14]:='E';
Heap [ 15]:='F';
Heap [ 16]:='#';
Heap [ 17]:= char(0);
Heap [ 64]:='c';
Heap [ 65]:='.';
Heap [ 66]:='d'; // p
Heap [ 67]:='e'; // r
Heap [ 68]:='f'; // g
Heap [ 69]:= char(0);
nHeap := 70;
Sym [ 1]:= 16; // #
nSym := 2;
end
word Stop() is
nStk:=0;
while nLine!=0 do
Stk[nStk]:=nLine%10;
nStk :=nStk+1;
nLine :=nLine/10;
end
while nStk !=0 do
nStk :=nStk-1;
putc(char(Stk[nStk]+48));
end
close();
halt ();
end
word val () is
word E:=10;
word J:= 0;
if Buff[0]='0' then
if Buff[1]='x' then
E:=16;
J:= 2;
end
end
word N:=0;
while Buff[J]!=char(0) do
word K:=0;
while Heap[K]!=Buff[J] do
if K=E then
Stop();
end
K:=K+1;
end
N:=E*N;
N:=N+K;
J:=J+1;
end
return N;
end
word Copy() is
word pHeap:=nHeap;
word pBuff:=0;
while Buff[pBuff]!=char(0) do
Heap[nHeap]:= Buff[pBuff];
nHeap :=nHeap+1;
pBuff :=pBuff+1;
end
Heap[nHeap]:=char(0);
nHeap :=nHeap+1;
return pHeap;
end
word Comp(word pHeap) is
word pBuff:=0;
while Buff[pBuff]=Heap[pHeap] do
if Buff[pBuff]=char(0) then
return 0;
end
pHeap:=pHeap+1;
pBuff:=pBuff+1;
end
return 1;
end
char Look() is
if pText>=nText then
pText:=0;
nText:=read();
if pText>=nText then
return char(0);
end
end
return Text[pText];
end
char Read() is
char C:=Look();
pText :=pText+1;
return C;
end
word isalpha (char C) is
if 'A'<=C then
if C<='Z' then
return 0;
end
end
if 'a'<=C then
if C<='z' then
return 0;
end
end
return 1;
end
word isnumber(char C) is
if '0'<=C then
if C<='9' then
return 0;
end
end
return 1;
end
word isalnum (char C) is
if isalpha (C)=0 then
return 0;
end
if isnumber(C)=0 then
return 0;
end
return 1;
end
word Digraph(char C1, char C2) is
if Buff[0]=C1 then
if Look()=C2 then
Buff[1]:=Read();
Buff[2]:=char(0);
end
end
end
char Scan() is
word pBuff:=0;
while pBuff =0 do
word sFlag:=0;
while sFlag =0 do
if Look()!=char( 9) then
if Look()!=char(10) then
if Look()!=char(13) then
if Look()!=char(32) then
sFlag:=1;
end
end
end
end
if sFlag=0 then
if Read()=char(10) then
nLine:=nLine+1;
end
end
end
//if pBuff=0 then
while isalnum(Look())=0 do
Buff[pBuff]:= Read();
pBuff :=pBuff+1;
end
//end
if pBuff=0 then
Buff[pBuff]:= Read();
pBuff :=pBuff+1;
end
if Buff[0]=''' then
Buff[pBuff]:=Read(); // char
pBuff :=pBuff+1;
Buff[pBuff]:=Read(); // '
pBuff :=pBuff+1;
end
Buff[pBuff] :=char(0);
Digraph('<', '=');
Digraph('!', '=');
Digraph('>', '=');
Digraph(':', '=');
if Buff[0]='/' then
if Look()='/' then
while Look()!=char(10) do
if Read()=char( 0) then
Stop();
end
end
pBuff:=0;
end
end
end
end
word pSymb;
word pProg;
word L;
word V;
word Alter() is
L:=1;
word pName:=0;
while pName <nName do
word pHeap:=Name[pName];
if Heap[pHeap]!=char(0) then
if Comp(pHeap)=0 then
L:=pSymb+2;
//L:=L+Cls[pName];
V:=pName;
if Cls [pName]=0 then
L:=Ofs [pName];
V:=Size[pName];
end
return L;
end
end
pName:=pName+1;
end
if Buff[0]=''' then
L:=pSymb;
V:= word(Buff[1]);
end
if isnumber(Buff[0])=0 then
L:=pSymb+1;
V:= val ();
end
if isalpha (Buff[0])=0 then
L:=pSymb+2;
//V:= Copy();
end
return L;
end
word Find() is
word I:=1;
while I<nSym do
if Comp(Sym[I])=0 then
return I;
end
I:=I+1;
end
Sym [nSym]:= Copy();
nSym :=nSym +1;
return I;
end
word IsEnd() is
Scan();
if Buff[0]!='|' then
if Buff[0]!=';' then
if Buff[0]!='.' then
return 1;
end
end
end
return 0;
end
word AddSym(word pSym) is
Right[nRight]:=pSym;
pLeft[nRight]:=nLeft;
nRight :=nRight+1;
end
word LoadGrammar() is
hFile := open();
pText := 0;
nText := 0;
nLine := 1;
pSymb :=nSym;
nName := 0;
Buff[0] := ';';
while Buff[0]= ';' do
Scan();
word pSym:=Find();
Scan();
if Buff[0]!=';' then
Name[nName]:= Sym [pSym];
if Buff[0]='"' then
Scan();
Name[nName]:=Copy();
Scan(); // "
Scan();
end
Cls [nName]:= val ();
Scan();
Size[nName]:= val ();
Ofs [nName]:=pSym;
nName :=nName+1;
Scan(); // ;
end
end
pProg :=nSym;
nLeft := 0;
nRight := 0;
Buff[0] := ';';
while Buff[0]= ';' do
Scan();
word pSym:=Find();
Scan();
Buff[0]:='|';
while Buff[0]='|' do
Scan();
Left [nLeft]:=pSym;
Id [nLeft]:= val();
pRight[nLeft]:=nRight;
while IsEnd()!=0 do
AddSym(Find());
end
AddSym(0);
nLeft :=nLeft+1;
end
end
close();
end
word PrintSym(word pSym) is
word nChar:=0;
word pHeap:=Sym[pSym];
while Heap[pHeap]!=char(0) do
putc(Heap[pHeap]);
nChar:=nChar+1;
pHeap:=pHeap+1;
end
return nChar;
end
char ListGrammar() is
word pL:=0;
while pL<nLeft do
word nChar:=PrintSym(Left[pL]);
while nChar<13 do
putc(' ');
nChar:=nChar+1;
end
putc(' ');
putc(':');
word pR:=pRight[pL];
while Right[pR]!=0 do
while nChar<13 do
putc(' ');
nChar:=nChar+1;
end
putc(' ');
nChar:=PrintSym(Right[pR]);
pR :=pR+1;
end
putc(char(13));
putc(char(10));
pL:=pL+1;
end
end
begin
Init();
LoadGrammar();
ListGrammar();
end