Inferring nested static[T]

[andreaferretti]

This does not work

proc outSize[M: static[int], A](xs: array[M, A]): int = M

echo outSize([1, 2, 3, 4])

failing with Error: cannot generate code for: M.

In itself, this is not an issue: I think it has to do with array accepting a range as its first parameter, and it is enough to wrap it into a type with another name:

type Arr[N: static[int], A] = array[N, A]

proc outSize[M: static[int], A](xs: Arr[M, A]): int = M

echo outSize([1, 2, 3, 4]) # 4

It works for nested arrays as well:

echo outSize([
  [1, 2, 3],
  [4, 5, 6]
]) # 2

Unfortunately, trying to get the inner dimension fails:

proc inSize[M, N: static[int]](xs: Arr[M, Arr[N, int]]): int = N

echo inSize([
  [1, 2, 3],
  [4, 5, 6]
])

This fails with Error: cannot instantiate: 'N'. Unlike the previous example, I was not able to find a workaround for this

[yglukhov]

Latest nim devel now just crashes:

nim.nim(104)             nim
nim.nim(68)              handleCmdLine
main.nim(251)            mainCommand
main.nim(63)             commandCompileToC
modules.nim(214)         compileProject
modules.nim(162)         compileModule
passes.nim(203)          processModule
passes.nim(137)          processTopLevelStmt
sem.nim(458)             myProcess
sem.nim(432)             semStmtAndGenerateGenerics
semstmts.nim(1465)       semStmt
semexprs.nim(910)        semExprNoType
semexprs.nim(2172)       semExpr
semexprs.nim(1759)       semMagic
semexprs.nim(893)        semDirectOp
semexprs.nim(763)        semOverloadedCallAnalyseEffects
semcall.nim(342)         semOverloadedCall
semcall.nim(159)         resolveOverloads
semcall.nim(70)          pickBestCandidate
sigmatch.nim(1695)       matches
sigmatch.nim(1656)       matchesAux
sigmatch.nim(1509)       prepareOperand
semexprs.nim(26)         semOperand
semexprs.nim(2171)       semExpr
semexprs.nim(893)        semDirectOp
semexprs.nim(763)        semOverloadedCallAnalyseEffects
semcall.nim(342)         semOverloadedCall
semcall.nim(159)         resolveOverloads
semcall.nim(70)          pickBestCandidate
sigmatch.nim(1695)       matches
sigmatch.nim(1657)       matchesAux
sigmatch.nim(1430)       paramTypesMatch
sigmatch.nim(1300)       paramTypesMatchAux
sigmatch.nim(758)        typeRel
sigmatch.nim(593)        tryResolvingStaticExpr
semtypinst.nim(490)      replaceTypesInBody
semtypinst.nim(201)      replaceTypeVarsN
semexprs.nim(2255)       semExpr
semexprs.nim(746)        semStaticExpr
vm.nim(1481)             evalStaticExpr
system.nim(333)          evalConstExprAux
vmgen.nim(1767)          genExpr
vmgen.nim(1642)          gen
vmgen.nim(726)           genMagic
vmgen.nim(254)           genx
vmgen.nim(1632)          gen
SIGSEGV: Illegal storage access. (Attempt to read from nil?)

[andreaferretti]

Just wanted to mention that the following workaround works (and it is what I am using in linalg to infer matrix sizes)

type DoubleArray32[M, N: static[int]] = array[M, array[N, float32]]
type DoubleArray64[M, N: static[int]] = array[M, array[N, float64]]