Hi, I had merrily asumed I could implement nth Fibonacci number with:
takeOne(drop(recurrence!((a, n) => a[n-1] + a[n-2])(zero, one), n)).front
where zero and one are of type BigInt, and n is of type size_t. However both
dmd and ldc2 complain saying:
/usr/include/dmd/phobos/std/range/package.d(5770): Error: template
std.bigint.BigInt.opAssign cannot deduce function from argument types
!()(immutable(BigInt)) immutable, candidates are:
/usr/include/dmd/phobos/std/bigint.d(178):
std.bigint.BigInt.opAssign(T)(T x) if (isIntegral!T)
/usr/include/dmd/phobos/std/bigint.d(194): std.bigint.BigInt.opAssign(T
: BigInt)(T x)
/usr/include/dmd/phobos/std/range/package.d(5770): Error: template
std.bigint.BigInt.opAssign cannot deduce function from argument types
!()(immutable(BigInt)) immutable, candidates are:
/usr/include/dmd/phobos/std/bigint.d(178):
std.bigint.BigInt.opAssign(T)(T x) if (isIntegral!T)
/usr/include/dmd/phobos/std/bigint.d(194): std.bigint.BigInt.opAssign(T
: BigInt)(T x)
fibonacci.d(25): Error: template instance
`fibonacci.declarative.recurrence!((a, n) => a[n - 1] + a[n - 2],
immutable(BigInt), immutable(BigInt))` error instantiating
/usr/include/dmd/phobos/std/range/package.d(5720): Error: template
std.bigint.BigInt.opAssign cannot deduce function from argument types
!()(immutable(BigInt)) immutable, candidates are:
/usr/include/dmd/phobos/std/bigint.d(178):
std.bigint.BigInt.opAssign(T)(T x) if (isIntegral!T)
/usr/include/dmd/phobos/std/bigint.d(194): std.bigint.BigInt.opAssign(T
: BigInt)(T x)
/usr/include/dmd/phobos/std/range/package.d(3177): Error: template instance
`std.range.primitives.isInputRange!(Recurrence!(__lambda2, immutable(BigInt),
2LU))` error instantiating
fibonacci.d(25): Error: template std.range.drop cannot deduce function from
argument types !()(Recurrence!(__lambda2, immutable(BigInt), 2LU),
immutable(ulong)), candidates are:
/usr/include/dmd/phobos/std/range/package.d(3176): std.range.drop(R)(R
range, size_t n) if (isInputRange!R)
I am now at the WTF stage – how can I show this example on Thursday in my
DevoxxUK presentation?
I am close to giving up and imbibing of too much Pernod.
--
Russel.
===========================================
Dr Russel Winder t: +44 20 7585 2200
41 Buckmaster Road m: +44 7770 465 077
London SW11 1EN, UK w: www.russel.org.uk
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