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big: Add mod and addmod.

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This commit is contained in:
Jeroen van Rijn
2021-07-26 14:55:03 +02:00
parent 1ebaa9fb3b
commit 5f7aeb3045
2 changed files with 54 additions and 8 deletions
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52
core/math/big/basic.odin
View File

@@ -662,14 +662,60 @@ int_div :: proc(quotient, remainder, numerator, denominator: ^Int) -> (err: Erro
*/
if quotient == nil && remainder == nil { return .None; }
if err = clear_if_uninitialized(numerator); err != .None { return err; }
if err = clear_if_uninitialized(denominator); err != .None { return err; }
return _int_div_small(quotient, remainder, numerator, denominator);
z: bool;
if z, err = is_zero(denominator); z { return .Division_by_Zero; }
/*
If numerator < denominator then quotient = 0, remainder = numerator.
*/
c: int;
if c, err = cmp_mag(numerator, denominator); c == -1 {
if remainder != nil {
if err = copy(remainder, numerator); err != .None { return err; }
}
if quotient != nil {
zero(quotient);
}
return .None;
}
if false && (denominator.used > 2 * _MUL_KARATSUBA_CUTOFF) && (denominator.used <= (numerator.used/3) * 2) {
// err = _int_div_recursive(quotient, remainder, numerator, denominator);
} else if false {
// err = _int_div_school(quotient, remainder, numerator, denominator);
} else {
err = _int_div_small(quotient, remainder, numerator, denominator);
}
return err;
}
div :: proc{ int_div, };
/*
remainder = numerator % denominator.
0 <= remainder < denominator if denominator > 0
denominator < remainder <= 0 if denominator < 0
*/
int_mod :: proc(remainder, numerator, denominator: ^Int) -> (err: Error) {
if err = div(nil, remainder, numerator, denominator); err != .None { return err; }
z: bool;
if z, err = is_zero(remainder); z || denominator.sign == remainder.sign { return .None; }
return add(remainder, remainder, numerator);
}
mod :: proc { int_mod, };
/*
remainder = (number + addend) % modulus.
*/
int_addmod :: proc(remainder, number, addend, modulus: ^Int) -> (err: Error) {
if err = add(remainder, number, addend); err != .None { return err; }
return mod(remainder, remainder, modulus);
}
addmod :: proc { int_addmod, };
/*
==========================
@@ -974,7 +1020,7 @@ _int_sqr :: proc(dest, src: ^Int) -> (err: Error) {
}
/*
Fivide by three (based on routine from MPI and the GMP manual).
Divide by three (based on routine from MPI and the GMP manual).
*/
_int_div_3 :: proc(quotient, numerator: ^Int) -> (remainder: int, err: Error) {
/*

10
core/math/big/example.odin
View File

@@ -67,16 +67,16 @@ demo :: proc() {
destination, source, quotient, remainder, numerator, denominator := &Int{}, &Int{}, &Int{}, &Int{}, &Int{}, &Int{};
defer destroy(destination, source, quotient, remainder, numerator, denominator);
err = set (numerator, 2);
err = set (denominator, 3);
err = zero(quotient);
err = set (numerator, 3);
err = set (denominator, 2);
err = set (quotient, 3);
err = zero(remainder);
err = pow(numerator, numerator, 260);
err = addmod(remainder, numerator, denominator, quotient);
if err != .None {
fmt.printf("Error: %v\n", err);
} else {
print("numerator ", numerator, 16);
print("numerator ", numerator, 10);
print("denominator", denominator, 10);
print("quotient ", quotient, 10);
print("remainder ", remainder, 10);