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#
#
# Nim's Runtime Library
# (c) Copyright 2020 Nim contributors
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
import std/macros
from std/typetraits import OrdinalEnum, HoleyEnum
when defined(nimPreviewSlimSystem):
import std/assertions
# xxx `genEnumCaseStmt` needs tests and runnableExamples
macro genEnumCaseStmt*(typ: typedesc, argSym: typed, default: typed,
userMin, userMax: static[int], normalizer: static[proc(s :string): string]): untyped =
# Generates a case stmt, which assigns the correct enum field given
# a normalized string comparison to the `argSym` input.
# string normalization is done using passed normalizer.
let typ = typ.getTypeInst[1]
let typSym = typ.getTypeImpl.getTypeInst # skip aliases etc to get type sym
let impl = typSym.getImpl[2]
expectKind impl, nnkEnumTy
let normalizerNode = quote: `normalizer`
expectKind normalizerNode, nnkSym
result = nnkCaseStmt.newTree(newCall(normalizerNode, argSym))
# stores all processed field strings to give error msg for ambiguous enums
var foundFields: seq[string] = @[]
var fVal = ""
var fStr = "" # string of current field
var fNum = BiggestInt(0) # int value of current field
for f in impl:
case f.kind
of nnkEmpty: continue # skip first node of `enumTy`
of nnkSym, nnkIdent:
fVal = f.strVal
fStr = fVal
of nnkAccQuoted:
fVal = ""
for ch in f:
fVal.add ch.strVal
fStr = fVal
of nnkEnumFieldDef:
fVal = f[0].strVal
case f[1].kind
of nnkStrLit:
fStr = f[1].strVal
of nnkTupleConstr:
fStr = f[1][1].strVal
fNum = f[1][0].intVal
of nnkIntLit:
fStr = f[0].strVal
fNum = f[1].intVal
else:
let fAst = f[0].getImpl
if fAst.kind == nnkStrLit:
fStr = fAst.strVal
else:
error("Invalid tuple syntax!", f[1])
else: error("Invalid node for enum type `" & $f.kind & "`!", f)
# add field if string not already added
if fNum >= userMin and fNum <= userMax:
fStr = normalizer(fStr)
if fStr notin foundFields:
result.add nnkOfBranch.newTree(newLit fStr, newDotExpr(typ, ident fVal))
foundFields.add fStr
else:
error("Ambiguous enums cannot be parsed, field " & $fStr &
" appears multiple times!", f)
inc fNum
# finally add else branch to raise or use default
if default == nil:
let raiseStmt = quote do:
raise newException(ValueError, "Invalid enum value: " & $`argSym`)
result.add nnkElse.newTree(raiseStmt)
else:
expectKind(default, nnkSym)
result.add nnkElse.newTree(default)
macro enumFullRange(a: typed): untyped =
newNimNode(nnkBracket).add(a.getType[1][1..^1])
macro enumNames(a: typed): untyped =
# this could be exported too; in particular this could be useful for enum with holes.
result = newNimNode(nnkBracket)
for ai in a.getType[1][1..^1]:
assert ai.kind == nnkSym
result.add newLit ai.strVal
iterator items*[T: HoleyEnum](E: typedesc[T]): T =
## Iterates over an enum with holes.
runnableExamples:
type
A = enum
a0 = 2
a1 = 4
a2
B[T] = enum
b0 = 2
b1 = 4
from std/sequtils import toSeq
assert A.toSeq == [a0, a1, a2]
assert B[float].toSeq == [B[float].b0, B[float].b1]
for a in enumFullRange(E): yield a
func span(T: typedesc[HoleyEnum]): int =
(T.high.ord - T.low.ord) + 1
const invalidSlot = uint8.high
proc genLookup[T: typedesc[HoleyEnum]](_: T): auto =
const n = span(T)
var i = 0
assert n <= invalidSlot.int
var ret {.noinit.}: array[n, uint8]
for ai in mitems(ret): ai = invalidSlot
for ai in items(T):
ret[ai.ord - T.low.ord] = uint8(i)
inc(i)
return ret
func symbolRankImpl[T](a: T): int {.inline.} =
const n = T.span
const thres = 255 # must be <= `invalidSlot`, but this should be tuned.
when n <= thres:
const lookup = genLookup(T)
let lookup2 {.global.} = lookup # xxx improve pending https://github.com/timotheecour/Nim/issues/553
#[
This could be optimized using a hash adapted to `T` (possible since it's known at CT)
to get better key distribution before indexing into the lookup table table.
]#
{.noSideEffect.}: # because it's immutable
let ret = lookup2[ord(a) - T.low.ord]
if ret != invalidSlot: return ret.int
else:
var i = 0
# we could also generate a case statement as optimization
for ai in items(T):
if ai == a: return i
inc(i)
raise newException(IndexDefect, $ord(a) & " invalid for " & $T)
template symbolRank*[T: enum](a: T): int =
## Returns the index in which `a` is listed in `T`.
##
## The cost for a `HoleyEnum` is implementation defined, currently optimized
## for small enums, otherwise is `O(T.enumLen)`.
runnableExamples:
type
A = enum # HoleyEnum
a0 = -3
a1 = 10
a2
a3 = (20, "f3Alt")
B = enum # OrdinalEnum
b0
b1
b2
C = enum # OrdinalEnum
c0 = 10
c1
c2
assert a2.symbolRank == 2
assert b2.symbolRank == 2
assert c2.symbolRank == 2
assert c2.ord == 12
assert a2.ord == 11
var invalid = 7.A
doAssertRaises(IndexDefect): discard invalid.symbolRank
when T is Ordinal: ord(a) - T.low.ord.static
else: symbolRankImpl(a)
proc rangeBase(T: typedesc): typedesc {.magic: "TypeTrait".}
# skip one level of range; return the base type of a range type
func symbolName*[T: enum](a: T): string =
## Returns the symbol name of an enum.
##
## This uses `symbolRank`.
runnableExamples:
type B = enum
b0 = (10, "kb0")
b1 = "kb1"
b2
let b = B.low
assert b.symbolName == "b0"
assert $b == "kb0"
static: assert B.high.symbolName == "b2"
type C = enum # HoleyEnum
c0 = -3
c1 = 4
c2 = 20
assert c1.symbolName == "c1"
when T is range:
const names = enumNames(rangeBase T)
else:
const names = enumNames(T)
names[a.symbolRank]
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