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https://github.com/RGBCube/serenity
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Calculator: Change internal representation to support perfect division
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.
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10 changed files with 110 additions and 361 deletions
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@ -7,38 +7,31 @@
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*/
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#include "Keypad.h"
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#include "KeypadValue.h"
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#include <AK/IntegralMath.h>
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#include <AK/StringBuilder.h>
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#include <LibCrypto/BigFraction/BigFraction.h>
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#include <LibCrypto/BigInt/UnsignedBigInteger.h>
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#include <LibCrypto/NumberTheory/ModularFunctions.h>
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void Keypad::type_digit(int digit)
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{
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u64 previous_value = 0;
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switch (m_state) {
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case State::External:
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m_state = State::TypingInteger;
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m_negative = false;
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m_int_value = digit;
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m_frac_value = 0;
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m_frac_length = 0;
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m_frac_value.set_to_0();
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m_frac_length.set_to_0();
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break;
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case State::TypingInteger:
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VERIFY(m_frac_value.value() == 0);
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VERIFY(m_frac_value == 0);
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VERIFY(m_frac_length == 0);
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previous_value = m_int_value.value();
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m_int_value *= 10;
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m_int_value += digit;
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if (m_int_value.has_overflow())
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m_int_value = previous_value;
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m_int_value.set_to(m_int_value.multiplied_by(10));
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m_int_value.set_to(m_int_value.plus(digit));
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break;
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case State::TypingDecimal:
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previous_value = m_frac_value.value();
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m_frac_value *= 10;
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m_frac_value += digit;
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if (m_frac_value.has_overflow())
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m_frac_value = previous_value;
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else
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m_frac_length++;
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m_frac_value.set_to(m_frac_value.multiplied_by(10));
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m_frac_value.set_to(m_frac_value.plus(digit));
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m_frac_length.set_to(m_frac_length.plus(1));
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break;
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}
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}
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@ -47,14 +40,13 @@ void Keypad::type_decimal_point()
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{
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switch (m_state) {
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case State::External:
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m_negative = false;
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m_int_value = 0;
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m_frac_value = 0;
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m_frac_length = 0;
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m_int_value.set_to_0();
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m_frac_value.set_to_0();
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m_frac_length.set_to_0();
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m_state = State::TypingDecimal;
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break;
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case State::TypingInteger:
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VERIFY(m_frac_value.value() == 0);
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VERIFY(m_frac_value == 0);
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VERIFY(m_frac_length == 0);
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m_state = State::TypingDecimal;
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break;
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@ -68,70 +60,78 @@ void Keypad::type_backspace()
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{
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switch (m_state) {
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case State::External:
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m_negative = false;
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m_int_value = 0;
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m_frac_value = 0;
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m_frac_length = 0;
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m_int_value.set_to_0();
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m_frac_value.set_to_0();
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m_frac_length.set_to_0();
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break;
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case State::TypingDecimal:
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if (m_frac_length > 0) {
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m_frac_value /= 10;
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m_frac_length--;
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m_frac_value.set_to(m_frac_value.divided_by(10).quotient);
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m_frac_length.set_to(m_frac_length.minus(1));
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break;
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}
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VERIFY(m_frac_value.value() == 0);
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VERIFY(m_frac_value == 0);
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m_state = State::TypingInteger;
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[[fallthrough]];
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case State::TypingInteger:
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VERIFY(m_frac_value.value() == 0);
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VERIFY(m_frac_value == 0);
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VERIFY(m_frac_length == 0);
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m_int_value /= 10;
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if (m_int_value.value() == 0)
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m_negative = false;
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m_int_value.set_to(m_int_value.divided_by(10).quotient);
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break;
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}
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}
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KeypadValue Keypad::value() const
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Crypto::BigFraction Keypad::value() const
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{
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KeypadValue frac_part = { (i64)m_frac_value.value(), m_frac_length };
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KeypadValue int_part = { (i64)m_int_value.value() };
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KeypadValue res = int_part + frac_part;
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if (m_negative)
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res = -res;
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return res;
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if (m_state != State::External) {
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Crypto::SignedBigInteger sum { m_int_value.multiplied_by(Crypto::NumberTheory::Power("10"_bigint, m_frac_length)).plus(m_frac_value) };
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Crypto::BigFraction res { move(sum), Crypto::NumberTheory::Power("10"_bigint, m_frac_length) };
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m_internal_value = move(res);
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}
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return m_internal_value;
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}
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void Keypad::set_value(KeypadValue value)
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void Keypad::set_value(Crypto::BigFraction value)
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{
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m_state = State::External;
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if (value.m_value < 0) {
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m_negative = true;
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value = -value;
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} else
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m_negative = false;
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m_internal_value = move(value);
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}
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m_int_value = value.m_value / AK::pow<u64>(10, value.m_decimal_places);
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m_frac_value = value.m_value % AK::pow<u64>(10, value.m_decimal_places);
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m_frac_length = value.m_decimal_places;
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void Keypad::set_to_0()
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{
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m_int_value.set_to_0();
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m_frac_value.set_to_0();
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m_frac_length.set_to_0();
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m_internal_value.set_to_0();
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m_state = State::External;
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}
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String Keypad::to_string() const
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{
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// TODO: Implement custom rounding length in the calculator.
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constexpr auto maximum_precision = 6;
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if (m_state == State::External)
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return m_internal_value.to_string(maximum_precision);
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StringBuilder builder;
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if (m_negative)
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builder.append('-');
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builder.appendff("{}", m_int_value.value());
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// NOTE: This is so the decimal point appears on screen as soon as you type it.
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if (m_frac_length > 0 || m_state == State::TypingDecimal)
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String const integer_value = m_int_value.to_base(10);
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String const frac_value = m_frac_value.to_base(10);
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unsigned const number_pre_zeros = m_frac_length.to_u64() - (frac_value.length() - 1) - (frac_value == "0" ? 0 : 1);
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builder.append(integer_value);
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// NOTE: We test for the state so the decimal point appears on screen as soon as you type it.
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if (m_state == State::TypingDecimal) {
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builder.append('.');
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if (m_frac_length > 0) {
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// FIXME: This disables the compiletime format string check since we can't parse '}}' here correctly.
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// remove the 'StringView { }' when that's fixed.
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builder.appendff("{:0{}}"sv, m_frac_value.value(), m_frac_length);
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builder.append_repeated('0', number_pre_zeros);
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if (frac_value != "0")
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builder.append(frac_value);
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}
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return builder.to_string();
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