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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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54
Userland/Applications/Calculator/Calculator.cpp
View file

@ -6,13 +6,13 @@
*/
#include "Calculator.h"
#include "KeypadValue.h"
#include <AK/Assertions.h>
#include <AK/Math.h>
#include <LibCrypto/BigFraction/BigFraction.h>
KeypadValue Calculator::begin_operation(Operation operation, KeypadValue argument)
Crypto::BigFraction Calculator::begin_operation(Operation operation, Crypto::BigFraction argument)
{
KeypadValue res = 0;
Crypto::BigFraction res {};
switch (operation) {
case Operation::None:
@ -27,7 +27,7 @@ KeypadValue Calculator::begin_operation(Operation operation, KeypadValue argumen
return argument;
case Operation::Sqrt:
if (argument < 0) {
if (argument < Crypto::BigFraction {}) {
m_has_error = true;
return argument;
}
@ -35,7 +35,7 @@ KeypadValue Calculator::begin_operation(Operation operation, KeypadValue argumen
clear_operation();
break;
case Operation::Inverse:
if (argument == 0) {
if (argument == Crypto::BigFraction {}) {
m_has_error = true;
return argument;
}
@ -43,14 +43,14 @@ KeypadValue Calculator::begin_operation(Operation operation, KeypadValue argumen
clear_operation();
break;
case Operation::Percent:
res = argument * KeypadValue { 1, 2 }; // also known as `KeypadValue{0.01}`
res = argument * Crypto::BigFraction { 1, 100 };
break;
case Operation::ToggleSign:
res = -argument;
break;
case Operation::MemClear:
m_mem = 0;
m_mem.set_to_0();
res = argument;
break;
case Operation::MemRecall:
@ -66,15 +66,12 @@ KeypadValue Calculator::begin_operation(Operation operation, KeypadValue argumen
break;
}
if (should_be_rounded(res))
round(res);
return res;
}
KeypadValue Calculator::finish_operation(KeypadValue argument)
Crypto::BigFraction Calculator::finish_operation(Crypto::BigFraction argument)
{
KeypadValue res = 0;
Crypto::BigFraction res {};
switch (m_operation_in_progress) {
case Operation::None:
@ -90,7 +87,7 @@ KeypadValue Calculator::finish_operation(KeypadValue argument)
res = m_saved_argument * argument;
break;
case Operation::Divide:
if (argument == 0) {
if (argument == Crypto::BigFraction {}) {
m_has_error = true;
return argument;
}
@ -108,9 +105,6 @@ KeypadValue Calculator::finish_operation(KeypadValue argument)
VERIFY_NOT_REACHED();
}
if (should_be_rounded(res))
round(res);
clear_operation();
return res;
}
@ -118,32 +112,6 @@ KeypadValue Calculator::finish_operation(KeypadValue argument)
void Calculator::clear_operation()
{
m_operation_in_progress = Operation::None;
m_saved_argument = 0;
m_saved_argument.set_to_0();
clear_error();
}
bool Calculator::should_be_rounded(KeypadValue value)
{
// We check if pow(10, value.m_decimal_places) overflow.
// If it does, the value can't be displayed (and provoke a division by zero), see Keypad::set_value()
// For u64, the threshold is 19
return value.m_decimal_places > rounding_threshold;
}
void Calculator::round(KeypadValue& value)
{
while (value.m_decimal_places > rounding_threshold) {
bool const need_increment = value.m_value % 10 > 4;
value.m_value /= 10;
if (need_increment)
value.m_value++;
value.m_decimal_places--;
if (value.m_value == 0) {
value = 0;
return;
}
}
}