pascal自定义函数问题

pascal自定义函数问题

var i,k:longint;
function ff(n:longint):longint;
while n<>6174 do
begin
t:=n;i:=0;
while t<>0 do
begin
i:=i+1;
a[i]:=t mod 10;
t:=t div 10;
end;
for i:=1 to 3 do
for j:=1 to 4-i do
if a[j]>a[j+1] then
begin
t:=a[j];a[j]:=a[j+1];a[j+1]:=t;
end;
min:=a[1]*1000+a[2]*100+a[3]*10+a[4];
max:=a[1]+a[2]*10+a[3]*100+a[4]*1000;
ff:=max-min;
writeln(max,'-',min,'=',ff);
end;
end;
begin
readln(k);ff(k);
end.追问
追答好吧，不要管他，只要看着像函数就行，对吧
那么
var i,k:longint;
function ff(n:longint):longint;
while n<>6174 do
begin
t:=n;i:=0;
while t<>0 do
begin
i:=i+1;
a[i]:=t mod 10;
t:=t div 10;
end;
for i:=1 to 3 do
for j:=1 to 4-i do
if a[j]>a[j+1] then
begin
t:=a[j];a[j]:=a[j+1];a[j+1]:=t;
end;
min:=a[1]*1000+a[2]*100+a[3]*10+a[4];
max:=a[1]+a[2]*10+a[3]*100+a[4]*1000;
n:=max-min;
writeln(max,'-',min,'=',n);
end;
end;
begin
readln(k);ff(k);
end.