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Calculator: Change internal representation to support perfect division

Browse source 
The purpose of this patch is to support addition, subtraction,
multiplication and division without using conversion to double. To this
end, we use the BigFraction class of LibCrypto. With this solution, we
can store values without any losses and forward rounding as the last
step before displaying.
This commit is contained in:
Lucas CHOLLET 2022-01-12 11:05:03 +01:00 • committed by Sam Atkins
parent 4ab8ad2ed2
commit 53eb35caba
10 changed files with 110 additions and 361 deletions
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122
Userland/Applications/Calculator/Keypad.cpp
View file

@ -7,38 +7,31 @@
*/
#include "Keypad.h"
#include "KeypadValue.h"
#include <AK/IntegralMath.h>
#include <AK/StringBuilder.h>
#include <LibCrypto/BigFraction/BigFraction.h>
#include <LibCrypto/BigInt/UnsignedBigInteger.h>
#include <LibCrypto/NumberTheory/ModularFunctions.h>
void Keypad::type_digit(int digit)
{
u64 previous_value = 0;
switch (m_state) {
case State::External:
m_state = State::TypingInteger;
m_negative = false;
m_int_value = digit;
m_frac_value = 0;
m_frac_length = 0;
m_frac_value.set_to_0();
m_frac_length.set_to_0();
break;
case State::TypingInteger:
VERIFY(m_frac_value.value() == 0);
VERIFY(m_frac_value == 0);
VERIFY(m_frac_length == 0);
previous_value = m_int_value.value();
m_int_value *= 10;
m_int_value += digit;
if (m_int_value.has_overflow())
m_int_value = previous_value;
m_int_value.set_to(m_int_value.multiplied_by(10));
m_int_value.set_to(m_int_value.plus(digit));
break;
case State::TypingDecimal:
previous_value = m_frac_value.value();
m_frac_value *= 10;
m_frac_value += digit;
if (m_frac_value.has_overflow())
m_frac_value = previous_value;
else
m_frac_length++;
m_frac_value.set_to(m_frac_value.multiplied_by(10));
m_frac_value.set_to(m_frac_value.plus(digit));
m_frac_length.set_to(m_frac_length.plus(1));
break;
}
}
@ -47,14 +40,13 @@ void Keypad::type_decimal_point()
{
switch (m_state) {
case State::External:
m_negative = false;
m_int_value = 0;
m_frac_value = 0;
m_frac_length = 0;
m_int_value.set_to_0();
m_frac_value.set_to_0();
m_frac_length.set_to_0();
m_state = State::TypingDecimal;
break;
case State::TypingInteger:
VERIFY(m_frac_value.value() == 0);
VERIFY(m_frac_value == 0);
VERIFY(m_frac_length == 0);
m_state = State::TypingDecimal;
break;
@ -68,70 +60,78 @@ void Keypad::type_backspace()
{
switch (m_state) {
case State::External:
m_negative = false;
m_int_value = 0;
m_frac_value = 0;
m_frac_length = 0;
m_int_value.set_to_0();
m_frac_value.set_to_0();
m_frac_length.set_to_0();
break;
case State::TypingDecimal:
if (m_frac_length > 0) {
m_frac_value /= 10;
m_frac_length--;
m_frac_value.set_to(m_frac_value.divided_by(10).quotient);
m_frac_length.set_to(m_frac_length.minus(1));
break;
}
VERIFY(m_frac_value.value() == 0);
VERIFY(m_frac_value == 0);
m_state = State::TypingInteger;
[[fallthrough]];
case State::TypingInteger:
VERIFY(m_frac_value.value() == 0);
VERIFY(m_frac_value == 0);
VERIFY(m_frac_length == 0);
m_int_value /= 10;
if (m_int_value.value() == 0)
m_negative = false;
m_int_value.set_to(m_int_value.divided_by(10).quotient);
break;
}
}
KeypadValue Keypad::value() const
Crypto::BigFraction Keypad::value() const
{
KeypadValue frac_part = { (i64)m_frac_value.value(), m_frac_length };
KeypadValue int_part = { (i64)m_int_value.value() };
KeypadValue res = int_part + frac_part;
if (m_negative)
res = -res;
return res;
if (m_state != State::External) {
Crypto::SignedBigInteger sum { m_int_value.multiplied_by(Crypto::NumberTheory::Power("10"_bigint, m_frac_length)).plus(m_frac_value) };
Crypto::BigFraction res { move(sum), Crypto::NumberTheory::Power("10"_bigint, m_frac_length) };
m_internal_value = move(res);
}
return m_internal_value;
}
void Keypad::set_value(KeypadValue value)
void Keypad::set_value(Crypto::BigFraction value)
{
m_state = State::External;
if (value.m_value < 0) {
m_negative = true;
value = -value;
} else
m_negative = false;
m_internal_value = move(value);
}
m_int_value = value.m_value / AK::pow<u64>(10, value.m_decimal_places);
m_frac_value = value.m_value % AK::pow<u64>(10, value.m_decimal_places);
m_frac_length = value.m_decimal_places;
void Keypad::set_to_0()
{
m_int_value.set_to_0();
m_frac_value.set_to_0();
m_frac_length.set_to_0();
m_internal_value.set_to_0();
m_state = State::External;
}
String Keypad::to_string() const
{
// TODO: Implement custom rounding length in the calculator.
constexpr auto maximum_precision = 6;
if (m_state == State::External)
return m_internal_value.to_string(maximum_precision);
StringBuilder builder;
if (m_negative)
builder.append('-');
builder.appendff("{}", m_int_value.value());
// NOTE: This is so the decimal point appears on screen as soon as you type it.
if (m_frac_length > 0 || m_state == State::TypingDecimal)
String const integer_value = m_int_value.to_base(10);
String const frac_value = m_frac_value.to_base(10);
unsigned const number_pre_zeros = m_frac_length.to_u64() - (frac_value.length() - 1) - (frac_value == "0" ? 0 : 1);
builder.append(integer_value);
// NOTE: We test for the state so the decimal point appears on screen as soon as you type it.
if (m_state == State::TypingDecimal) {
builder.append('.');
if (m_frac_length > 0) {
// FIXME: This disables the compiletime format string check since we can't parse '}}' here correctly.
// remove the 'StringView { }' when that's fixed.
builder.appendff("{:0{}}"sv, m_frac_value.value(), m_frac_length);
builder.append_repeated('0', number_pre_zeros);
if (frac_value != "0")
builder.append(frac_value);
}
return builder.to_string();