nim-stint/tests/test_uint_addsub.nim

77 lines
2.0 KiB
Nim

# Stint
# Copyright 2018 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
suite "Testing unsigned int addition implementation":
test "In-place addition gives expected result":
var a = 20182018.stuint(64)
let b = 20172017.stuint(64)
a += b
check: cast[uint64](a) == 20182018'u64 + 20172017'u64
test "Addition gives expected result":
let a = 20182018.stuint(64)
let b = 20172017.stuint(64)
check: cast[uint64](a+b) == 20182018'u64 + 20172017'u64
test "When the low half overflows, it is properly carried":
# uint8 (low half) overflow at 255
let a = 100'u16.stuint(16)
let b = 100'u16.stuint(16)
check: cast[uint16](a+b) == 200
test "Full overflow is handled like native unsigned types":
# uint16 overflows after 65535
let a = 100'u16.stuint(16)
var z = 0'u16.stuint(16)
let o = 36'u16.stuint(16)
for _ in 0 ..< 655:
z += a
check: cast[uint16](z) == 65500
check: cast[uint16](z + o) == 0
z += a
check: cast[uint16](z) == 64
z += a
check: cast[uint16](z) == 164
suite "Testing unsigned int substraction implementation":
test "In-place substraction gives expected result":
var a = 20182018.stuint(64)
let b = 20172017.stuint(64)
a -= b
check: cast[uint64](a) == 20182018'u64 - 20172017'u64
test "Substraction gives expected result":
let a = 20182018.stuint(64)
let b = 20172017.stuint(64)
check: cast[uint64](a-b) == 20182018'u64 - 20172017'u64
test "Full overflow is handled like native unsigned types":
# uint16 overflows after 65535
let a = 100'u16.stuint(16)
let b = 101'u16.stuint(16)
check: cast[uint16](a-b) == high(uint16)