Data update

Task/Factorial/Pascal/factorial-2.pas

@@ -1,32 +1,45 @@
 {$mode objFPC}{R+}
-FUNCTION Factorial ( n : qword ) : qword;
+FUNCTION Fact(n: qword): qword;
 
-    (*)
-           Update for version 3.2.0
-           Factorial works until 20! , which is good enough for me for now
-           replace qword with dword and rax,rcx with eax, ecx for 32-bit
-           for Factorial until 12!
-    (*)
+VAR
+    F: qword;
 
-    VAR
-	
-	F:	qword;
-	
-    BEGIN
+BEGIN
+    if n > 20 then
+    begin
+        WriteLn('This function is only accurate up to 20!');
+        exit(0);
+    end;
 
-	asm
-	
-		mov		$1,	%rax
-		mov		 n,	%rcx
-		
-	.Lloop1:
-			imul	%rcx,	%rax
-			loopnz	.Lloop1
-		
-		mov	%rax,   F
+    asm
+        (*) Initialize result = 1 (0! = 1 case handled automatically) (*)
 
-	end;
+        mov     $1, %rax          (*)  RAX = 1 (initial result)       (*)
+        mov      n, %rcx          (*)  RCX = input number (counter)   (*)
 
-	Result := F ;
-	
-    END;
+        test    %rcx, %rcx        (*)  Check if n=0                   (*)
+        jz      .Lstore_result    (*)  Skip loop if n=0               (*)
+
+    .Lloop1:
+        imul    %rcx, %rax        (*)  RAX = RAX * RCX (signed mul)   (*)
+        dec     %rcx              (*)  Decrement RCX                  (*)
+        jnz     .Lloop1           (*)  Loop while RCX != 0            (*)
+
+    .Lstore_result:
+        mov     %rax, F           (*)  Store result in F              (*)
+    end ['rax', 'rcx'];           (*)  Tell compiler register change  (*)
+
+    Result := F;
+
+END;
+
+
+var
+    N       : integer = 20 ;
+
+begin
+
+    writeln;
+    writeln( BasicFact(N));
+
+end.        (*)    Function Fact    (*)

Task/Factorial/Pascal/factorial-3.pas

@@ -1,92 +1,33 @@
-PROGRAM EXBigFac ;
+program GMPfact;
 
-{$IFDEF FPC}
-    {$mode objfpc}{$H+}{$J-}{R+}
-{$ELSE}
-    {$APPTYPE CONSOLE}
-{$ENDIF}
+{$mode objfpc}
 
-(*)
+uses
 
-        Free Pascal Compiler version 3.2.0 [2020/06/14] for x86_64
-        The free and readable alternative at C/C++ speeds
-        compiles natively to almost any platform, including raspberry PI *
-        Can run independently from DELPHI / Lazarus
+    gmp
+    ;
 
-        For debian Linux: apt -y install fpc
-        It contains a text IDE called fp
+    function Factorial(n: qword): string;
+        var
+            ResultMPZ: mpz_t;
+            i: qword;
+        begin
+            mpz_init_set_ui(ResultMPZ, 1);
+            for i := 2 to n do
+                mpz_mul_ui(ResultMPZ, ResultMPZ, i);
+            Result := mpz_get_str(nil, 10, ResultMPZ);
+            mpz_clear(ResultMPZ);
+        end;
 
-        https://www.freepascal.org/advantage.var
+var
+    N     : integer = 101 ;
+    Fact  :        string ;
 
-(*)
+begin
+    Fact := Factorial(101);
+    writeln( N ,'! = ', Fact);
+end.    (*)     GMPfact     (*)
 
 
-USES
-
-    gmp;
-
-    FUNCTION WriteBigNum ( c: pchar ) : ansistring ;
-
-    CONST
-
-        CrLf = #13 + #10 ;
-
-    VAR
-        i:              longint;
-        len:            longint;
-        preview:        integer;
-        ret:    ansistring = '';
-        threshold:      integer;
-
-    BEGIN
-
-        len		:=	length ( c ) ;
-        WriteLn ( 'Digits:  ', len ) ;
-        threshold	:= 12 ;
-        preview 	:= len div threshold ;
-
-        IF	( len < 91 ) THEN
-            BEGIN
-                FOR i := 0 TO len DO
-                    ret:= ret + c [ i ] ;
-            END
-        ELSE
-            BEGIN
-                FOR i := 0 TO preview DO
-                    ret:= ret + c [ i ] ;
-                    ret:= ret + '...'  ;
-                FOR i := len - preview -1  TO len DO
-                    ret:= ret + c [ i ] ;
-            END;
-        ret:= ret + CrLf ;
-        WriteBigNum := ret;
-    END;
-
-    FUNCTION BigFactorial ( n : qword ) : ansistring ;
-
-    (*)
-	See https://gmplib.org/#DOC
-    (*)
-
-    VAR
-        S:	mpz_t;
-        c:	pchar;
-
-    BEGIN
-
-        mpz_init_set_ui          ( S, 1 ) ;
-        mpz_fac_ui               ( S, n ) ;
-        c := mpz_get_str   ( NIL, 10, S ) ;
-        BigFactorial := WriteBigNum ( c ) ;
-
-    END;
-
-BEGIN
-
-    WriteLn ( BigFactorial ( 99 ) ) ;
-
-END.
-
 Output:
-Digits:  156
-93326215443944...00000000000000
+101! = 9425947759838359420851623124482936749562312794702543768327889353416977599316221476503087861591808346911623490003549599583369706302603264000000000000000000000000