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import std/decls
block:
var s = @[10,11,12]
var a {.byaddr.} = s[0]
a+=100
doAssert s == @[110,11,12]
doAssert a is int
var b {.byaddr.}: int = s[0]
doAssert a.addr == b.addr
doAssert not compiles(block:
# redeclaration not allowed
var foo = 0
var foo {.byaddr.} = s[0])
doAssert not compiles(block:
# ditto
var foo {.byaddr.} = s[0]
var foo {.byaddr.} = s[0])
block:
var b {.byaddr.} = s[1] # redeclaration ok in sub scope
b = 123
doAssert s == @[110,123,12]
b = b * 10
doAssert s == @[1100,123,12]
doAssert not compiles(block:
var b2 {.byaddr.}: float = s[2])
doAssert compiles(block:
var b2 {.byaddr.}: int = s[2])
## We can define custom pragmas in user code
template byUnsafeAddr(lhs, typ, expr) =
when typ is type(nil):
let tmp = unsafeAddr(expr)
else:
let tmp: ptr typ = unsafeAddr(expr)
template lhs: untyped = tmp[]
block:
let s = @["foo", "bar"]
let a {.byUnsafeAddr.} = s[0]
doAssert a == "foo"
doAssert a[0].unsafeAddr == s[0][0].unsafeAddr
block: # nkAccQuoted
# shows using a keyword, which requires nkAccQuoted
template `cast`(lhs, typ, expr) =
when typ is type(nil):
let tmp = unsafeAddr(expr)
else:
let tmp: ptr typ = unsafeAddr(expr)
template lhs: untyped = tmp[]
block:
let s = @["foo", "bar"]
let a {.`byUnsafeAddr`.} = s[0]
doAssert a == "foo"
doAssert a[0].unsafeAddr == s[0][0].unsafeAddr
block:
let s = @["foo", "bar"]
let a {.`cast`.} = s[0]
doAssert a == "foo"
doAssert a[0].unsafeAddr == s[0][0].unsafeAddr
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