dds_basic.c

a c example of dds module

/* DDS-BASIC Interpreter (Version 1.00).
   by <[e-mail]> Diomidis Spinellis,
   this is a 1990 IOCCC (obfuscated C code) entry */

#define O(b,f,u,s,c,a)b(){int o=f();switch(*p++){X u:_ o s b();X c:_ o a b();default:p--;_ o;}}
#define t(e,d,_,C)X e:f=fopen(B+d,_);C;fclose(f)
#define U(y,z)while(p=Q(s,y))*p++=z,*p=' '
#define N for(i=0;i<11*R;i++)m[i]&&
#define I "%d %s\n",i,m[i]
#define X ;break;case
#define _ return
#define R 999
typedef char*A;int*C,E[R],L[R],M[R],P[R],l,i,j;char B[R],F[2];A m[12*R],malloc
(),p,q,x,y,z,s,d,f,fopen();A Q(s,o)A s,o;{for(x=s;*x;x++){for(y=x,z=o;*z&&*y==
*z;y++)z++;if(z>o&&!*z)_ x;}_	0;}main(){m[11*R]="E";while(puts("Ok"),gets(B)
)switch(*B){X'R':C=E;l=1;for(i=0;i<R;P[i++]=0);while(l){while(!(s=m[l]))l++;if
(!Q(s,"\"")){U("<>",'#');U("<=",'$');U(">=",'!');}d=B;while(*F=*s){*s=='"'&&j
++;if(j&1||!Q(" \t",F))*d++=*s;s++;}*d--=j=0;if(B[1]!='=')switch(*B){X'E':l=-1
X'R':B[2]!='M'&&(l=*--C)X'I':B[1]=='N'?gets(p=B),P[*d]=S():(*(q=Q(B,"TH"))=0,p
=B+2,S()&&(p=q+4,l=S()-1))X'P':B[5]=='"'?*d=0,puts(B+6):(p=B+5,printf("%d\n",S
()))X'G':p=B+4,B[2]=='S'&&(*C++=l,p++),l=S()-1 X'F':*(q=Q(B,"TO"))=0;p=B+5;P[i
=B[3]]=S();p=q+2;M[i]=S();L[i]=l X'N':++P[*d]<=M[*d]&&(l=L[*d]);}else p=B+2,P[
*B]=S();l++;}X'L':N printf(I)X'N':N free(m[i]),m[i]=0	X'B':_ 0 t('S',5,"w",N
fprintf(f,I))t('O',4,"r",while(fgets(B,R,f))(*Q(B,"\n")=0,G()))X 0:default:G()
;}_ 0;}G(){l=atoi(B);m[l]&&free(m[l]);(p=Q(B," "))?strcpy(m[l]=malloc(strlen(p
)),p+1):(m[l]=0,0);}O(S,J,'=',==,'#',!=)O(J,K,'<',<,'>',>)O(K,V,'$',<=,'!',>=)
O(V,W,'+',+,'-',-)O(W,Y,'*',*,'/',/)Y(){int o;_*p=='-'?p++,-Y():*p>='0'&&*p<=
'9'?strtol(p,&p,0):*p=='('?p++,o=S(),p++,o:P[*p++];}

/*
    author:

	Diomidis Spinellis
	Imperial College, University of London
	Myrsinis 1
	GR-145 62 Kifissia
	Greece

    notes:

    The rules of the IOCCC require that the source code be public domain.
    
    Immediate commands:

	NEW
	LIST
	OLD filename
	RUN
	SAVE filename
	BYE

    Program statements:

	var = exp
	INPUT variable		
	PRINT string
	PRINT exp		
	GOTO exp	
	IF exp THEN exp
	FOR var = exp TO exp
	NEXT variable
	GOSUB exp		
	RETURN
	REM any text
	END

    Expressions (ranked by precedence):

	Bracketed expressions
	number (leading 0 for octal, 0x for hex, else decimal),
	variable
	Unary -
	* / 
	+ - 
	= <> 
	> < 
	<= >=
	(* and + are also used for boolean AND and boolean OR)
	(Boolean expressions evaluate to 0 for false and 1 for true)

    Variables:

	variable names a to z
	variables initialized to 0 on RUN

    Editing:

	- Line editor using line re-entry.
	- A line number with nothing following it, deletes the line.
	- Line number range	1-10000

    Input format:

	- ALL INPUT MUST BE UPPERCASE.
	- No space is allowed before the line number.
	- Exactly one space is needed between the OLD or SAVE command and 
	  the filename.

	No error checking is performed.
	The message 'core dumped' or 'bus error'
	signifies a syntax or semantic error.

*/