授業で作成した多倍長整数（30桁）を計算する電卓

calc.pas

program calc(input,output);
const DIGIT = 30;
type ary = array[0..DIGIT-1] of integer;
var a,b,c:ary; op:char;
procedure InputNum(var a:ary);
var ch:char;
  i:integer;
begin
	for i := 0 to DIGIT-1 do
		begin;
		read(ch);
		a[i] := ord(ch) - ord('0');
		end;
	readln();
end;
function DigitFind(a:ary):integer;
var i:integer;f:boolean;
begin
	f := true;
	for i := 0 to DIGIT-1 do
		if(a[i] <> 0) and f then 
		begin
		f := false;
		DigitFind := DIGIT - i;
		end;
end;
function MinFind(a:ary):boolean;
var i:integer;f:boolean;
begin
	f := false;
	for i := 0 to DIGIT-1 do
		begin
		if(a[i] < 0) then
			begin
			f := true;
			break;
			end;
		end;
	MinFind := not f;
end;
procedure OutputNum(a:ary);
var i:integer;
begin
	for i := 0 to DIGIT-1 do
		write(a[i]);
	writeln();
end;
procedure CopyArray(now:integer; var origin,obj:ary);
begin
	obj[now] := origin[now];
	origin[now] := 0;
	if (now - 1 > -1) then CopyArray(now - 1,origin,obj);
end;
procedure Add(a,b:ary;now:integer; var res:ary);
begin
	res[now] := res[now] + a[now] + b[now];
	if((res[now] div 10 > 0) and (now - 1 > -1)) then
		begin
		res[now - 1] := res[now - 1] + (res[now] div 10);
		res[now] := res[now] - ((res[now] div 10) * 10);
		end;
	if(now - 1 > -1) then Add(a,b,now-1,res);
end;
procedure SubTrac(a,b:ary;now:integer; var res:ary);
begin
//	OutputNum(res);
//	writeln(a[now],' ',b[now],' ',res[now]);
	res[now] := a[now] - b[now] - res[now];
//	writeln(res[now]);
	if((res[now] < 0) and (now - 1 > -1)) then
		begin
		res[now-1] := res[now-1] + 1;
		res[now] := res[now] + 10;
		end;
	if(now - 1 > -1) then SubTrac(a,b,now-1,res);
end;
procedure MulTrac(a,b:ary;now:integer; var res:ary);
var i,j:integer;
begin
	i := DIGIT - 1;
	j := now;
	while((i > -1) and (now > -1)) do
		begin
		res[j] := res[j] + (b[now] * a[i]);
		if((res[j] div 10 > 0) and (j - 1 > -1)) then
			begin
			res[j - 1] := res[j - 1] + (res[j] div 10);
			res[j] := res[j] - ((res[j] div 10) * 10);
			end;
		i := i - 1;
		j := j - 1;
		end;
	if(now - 1 > -1) then Multrac(a,b,now-1,res) 
end;
procedure Division(a,b:ary; var res:ary);
var adig,bdig,i,j,count,n:integer;
	ans:ary;
begin
	adig := DigitFind(a);
	bdig := DigitFind(b);
	CopyArray(DIGIT-1,ans,ans);
	if (adig >= bdig) then
		begin
		for i := (adig - bdig) to DIGIT-1 do
			b[i - (adig - bdig)] := b[i];
		for i := 1 to (adig - bdig) do
			b[DIGIT - i] := 0;
		n := adig - bdig;
		for i := n downto 0 do
			begin
			count := 0;
//			writeln('digit',' ',adig,' ',bdig,' ',i);
//			writeln(now);
//			OutputNum(a);
//			OutputNum(b);
//			OutputNum(res);
			SubTrac(a,b,(DIGIT-1),ans);
//			OutputNum(ans);
			while(MinFind(ans)) do	
				begin
//					OutputNum(ans);
//					writeln('t');
					CopyArray(DIGIT-1,ans,a);
					count := count + 1;
					SubTrac(a,b,(DIGIT-1),ans);
				end;
//			OutputNum(a);
//			writeln(res[DIGIT+now]);
//			if(res[DIGIT+now] div 10 > 0) then
//				begin
//				res[DIGIT+now-1] := res[DIGIT+now] div 10;
//				res[DIGIT+now] := res[DIGIT+now] mod 10;
//				end;
			if count > 0 then res[DIGIT-(i+1)] := count;
			for j := DIGIT-1 downto 1 do
				begin
				b[j] := b[j-1];
				end;
			b[0] := 0;
			CopyArray(DIGIT-1,ans,ans);
			end;
		end;
end;
begin
	InputNum(a);
	readln(op);
	while (op <> '=') do
		begin
		InputNum(b);
		if(op = '+') then Add(a,b,DIGIT-1,c)
		else if(op = '-') then SubTrac(a,b,DIGIT-1,c)
		else if(op = '*') then MulTrac(a,b,DIGIT-1,c)
		else if(op = '/') then Division(a,b,c); 
		CopyArray(DIGIT-1,c,a);
		OutputNum(a);
		readln(op);
		end;
	OutputNum(a);
end.