signed int exp

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jangko 2023-06-14 08:31:28 +07:00
parent 1657d841e7
commit 7b7db2a73a
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3 changed files with 92 additions and 9 deletions

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@ -184,12 +184,12 @@ func setBit*(a: var StInt, k: Natural) =
func clearBit*(a: var StInt, k: Natural) = func clearBit*(a: var StInt, k: Natural) =
## set bit at position `k` ## set bit at position `k`
## k = 0..a.bits-1 ## k = 0..a.bits-1
a.imp.clearBit(k) a.imp.clearBit(k)
func getBit*(a: StInt, k: Natural): bool = func getBit*(a: StInt, k: Natural): bool =
## set bit at position `k` ## set bit at position `k`
## k = 0..a.bits-1 ## k = 0..a.bits-1
a.imp.getBit(k) a.imp.getBit(k)
{.pop.} {.pop.}
@ -234,10 +234,29 @@ func `+=`*(a: var StInt, b: SomeUnsignedInt) =
{.push raises: [], noinit, gcsafe.} {.push raises: [], noinit, gcsafe.}
func pow*(a: StUint, e: Natural): StUint = func isOdd(x: Natural): bool =
bool(x and 1)
func pow*(a: StInt, e: Natural): StInt =
## Compute ``a`` to the power of ``e``, ## Compute ``a`` to the power of ``e``,
## ``e`` must be non-negative ## ``e`` must be non-negative
if a.isNegative:
func pow*[aBits, eBits](a: StUint[aBits], e: StUint[eBits]): StUint[aBits] = let base = a.neg
result.imp = base.imp.pow(e)
if e.isOdd:
result.negate
else:
result.imp = a.imp.pow(e)
func pow*[aBits, eBits](a: StInt[aBits], e: StInt[eBits]): StInt[aBits] =
## Compute ``x`` to the power of ``y``, ## Compute ``x`` to the power of ``y``,
## ``x`` must be non-negative ## ``x`` must be non-negative
doAssert e.isNegative.not, "exponent must be non-negative"
if a.isNegative:
let base = a.neg
result.imp = base.imp.pow(e.imp)
if e.isOdd:
result.negate
else:
result.imp = a.imp.pow(e.imp)

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@ -92,10 +92,10 @@ template testAddSub(chk, tst: untyped) =
chkNegation(chk, 32767, -32767, 128) chkNegation(chk, 32767, -32767, 128)
# With Nim 1.6, it seems like https://github.com/status-im/nim-stint/issues/92 # With Nim 1.6, it seems like https://github.com/status-im/nim-stint/issues/92
# can now happen on 32-bit platforms. # can now happen on 32-bit platforms.
when (NimMajor,NimMinor,NimPatch) < (1,6,0): #when (NimMajor,NimMinor,NimPatch) < (1,6,0):
chkNegation(chk, 2147483648, -2147483648, 128) chkNegation(chk, 2147483648, -2147483648, 128)
chkNegation(chk, 2147483647, -2147483647, 128) chkNegation(chk, 2147483647, -2147483647, 128)
#chkNegation(chk, 9223372036854775808, -9223372036854775808, 128) # TODO: bug #92 # chkNegation(chk, 9223372036854775808, -9223372036854775808, 128) # TODO: bug #92
tst "absolute integer": tst "absolute integer":
chkAbs(chk, 0, 0, 128) chkAbs(chk, 0, 0, 128)

64
tests/test_int_exp.nim Normal file
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@ -0,0 +1,64 @@
# Stint
# Copyright 2018-2023 Status Research & Development GmbH
# Licensed under either of
#
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
# * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
#
# at your option. This file may not be copied, modified, or distributed except according to those terms.
import ../stint, unittest, math, test_helpers
template chkPow(chk: untyped, a, b, c: string, bits: int) =
chk pow(fromHex(StInt[bits], a), fromHex(StInt[bits], b)) == fromHex(StInt[bits], c)
template chkPow(chk: untyped, a: string, b: SomeInteger, c: string, bits: int) =
chk pow(fromHex(StInt[bits], a), b) == fromHex(StInt[bits], c)
template testExp(chk, tst: untyped) =
tst "signed BigInt BigInt Pow":
chkPow(chk, "F", "2", "E1", 128)
chkPow(chk, "FF", "2", "FE01", 128)
chkPow(chk, "FF", "3", "FD02FF", 128)
chkPow(chk, "FFF", "3", "FFD002FFF", 128)
chkPow(chk, "FFFFF", "3", "ffffd00002fffff", 128)
chk pow(-10.i128, 2.i128) == 100.i128
chk pow(-10.i128, 3.i128) == -1000.i128
tst "signed BigInt Natural Pow":
chkPow(chk, "F", 2, "E1", 128)
chkPow(chk, "FF", 2, "FE01", 128)
chkPow(chk, "FF", 3, "FD02FF", 128)
chkPow(chk, "FFF", 3, "FFD002FFF", 128)
chkPow(chk, "FFFFF", 3, "ffffd00002fffff", 128)
chk pow(-10.i128, 2) == 100.i128
chk pow(-10.i128, 3) == -1000.i128
static:
testExp(ctCheck, ctTest)
suite "Wider signed int exp coverage":
testExp(check, test)
suite "Testing signed exponentiation":
test "Simple exponentiation 5^3":
let
a = 5'u64
b = 3
u = a.stint(64)
check:
cast[uint64](u.pow(b)) == a ^ b
cast[uint64](u.pow(b.stint(64))) == a ^ b
test "12 ^ 34 == 4922235242952026704037113243122008064":
# https://www.wolframalpha.com/input/?i=12+%5E+34
let
a = 12.stint(256)
b = 34
check: a.pow(b) == "4922235242952026704037113243122008064".i256
check: a.pow(b.stint(256)) == "4922235242952026704037113243122008064".i256