Merge pull request #25472 from JuliaLang/teh/find_sentinel

Change sentinel in find(first|next|prev|last) to `nothing`

Author: timholy

base/array.jl

@@ -1495,7 +1495,7 @@ cat(n::Integer, x::Integer...) = reshape([x...], (ntuple(x->1, n-1)..., length(x
 """
     findnext(A, i::Integer)
 
-Find the next linear index >= `i` of a `true` element of `A`, or `0` if not found.
+Find the next linear index >= `i` of a `true` element of `A`, or `nothing` if not found.
 
 # Examples
 ```jldoctest
@@ -1508,7 +1508,6 @@ julia> findnext(A, 1)
 2
 
 julia> findnext(A, 3)
-0
 ```
 """
 function findnext(A, start::Integer)
@@ -1526,14 +1525,14 @@ function findnext(A, start::Integer)
         end
         i = nextind(A, i)
     end
-    return 0
+    return nothing
 end
 
 """
     findfirst(A)
 
 Return the linear index of the first `true` value in `A`.
-Return `0` if no such value is found.
+Return `nothing` if no such value is found.
 To search for other kinds of values, pass a predicate as the first argument.
 
 # Examples
@@ -1546,16 +1545,17 @@ julia> A = [false false; true false]
 julia> findfirst(A)
 2
 
-julia> findfirst(falses(3))
-0
+julia> findfirst(falses(3)) == nothing
+true
 ```
 """
 findfirst(A) = findnext(A, 1)
 
 """
     findnext(predicate::Function, A, i::Integer)
 
-Find the next linear index >= `i` of an element of `A` for which `predicate` returns `true`, or `0` if not found.
+Find the next linear index >= `i` of an element of `A` for which `predicate` returns `true`,
+or `nothing` if not found.
 
 # Examples
 ```jldoctest
@@ -1567,8 +1567,8 @@ julia> A = [1 4; 2 2]
 julia> findnext(isodd, A, 1)
 1
 
-julia> findnext(isodd, A, 2)
-0
+julia> findnext(isodd, A, 2) == nothing
+true
 ```
 """
 function findnext(testf::Function, A, start::Integer)
@@ -1580,14 +1580,14 @@ function findnext(testf::Function, A, start::Integer)
         end
         i = nextind(A, i)
     end
-    return 0
+    return nothing
 end
 
 """
     findfirst(predicate::Function, A)
 
 Return the linear index of the first element of `A` for which `predicate` returns `true`.
-Return `0` if there is no such element.
+Return `nothing` if there is no such element.
 
 # Examples
 ```jldoctest
@@ -1599,8 +1599,8 @@ julia> A = [1 4; 2 2]
 julia> findfirst(iseven, A)
 2
 
-julia> findfirst(x -> x>10, A)
-0
+julia> findfirst(x -> x>10, A) == nothing
+true
 
 julia> findfirst(equalto(4), A)
 3
@@ -1611,7 +1611,7 @@ findfirst(testf::Function, A) = findnext(testf, A, 1)
 """
     findprev(A, i::Integer)
 
-Find the previous linear index <= `i` of a `true` element of `A`, or `0` if not found.
+Find the previous linear index <= `i` of a `true` element of `A`, or `nothing` if not found.
 
 # Examples
 ```jldoctest
@@ -1623,8 +1623,8 @@ julia> A = [false false; true true]
 julia> findprev(A,2)
 2
 
-julia> findprev(A,1)
-0
+julia> findprev(A,1) == nothing
+true
 ```
 """
 function findprev(A, start::Integer)
@@ -1639,14 +1639,14 @@ function findprev(A, start::Integer)
         a != 0 && return i
         i = prevind(A, i)
     end
-    return 0
+    return nothing
 end
 
 """
     findlast(A)
 
 Return the linear index of the last `true` value in `A`.
-Return `0` if there is no `true` value in `A`.
+Return `nothing` if there is no `true` value in `A`.
 
 # Examples
 ```jldoctest
@@ -1660,8 +1660,8 @@ julia> findlast(A)
 
 julia> A = falses(2,2);
 
-julia> findlast(A)
-0
+julia> findlast(A) == nothing
+true
 ```
 """
 findlast(A) = findprev(A, endof(A))
@@ -1670,7 +1670,7 @@ findlast(A) = findprev(A, endof(A))
     findprev(predicate::Function, A, i::Integer)
 
 Find the previous linear index <= `i` of an element of `A` for which `predicate` returns `true`, or
-`0` if not found.
+`nothing` if not found.
 
 # Examples
 ```jldoctest
@@ -1679,8 +1679,8 @@ julia> A = [4 6; 1 2]
  4  6
  1  2
 
-julia> findprev(isodd, A, 1)
-0
+julia> findprev(isodd, A, 1) == nothing
+true
 
 julia> findprev(isodd, A, 3)
 2
@@ -1692,14 +1692,14 @@ function findprev(testf::Function, A, start::Integer)
         testf(A[i]) && return i
         i = prevind(A, i)
     end
-    return 0
+    return nothing
 end
 
 """
     findlast(predicate::Function, A)
 
 Return the linear index of the last element of `A` for which `predicate` returns `true`.
-Return `0` if there is no such element.
+Return `nothing` if there is no such element.
 
 # Examples
 ```jldoctest
@@ -1711,8 +1711,8 @@ julia> A = [1 2; 3 4]
 julia> findlast(isodd, A)
 2
 
-julia> findlast(x -> x > 5, A)
-0
+julia> findlast(x -> x > 5, A) == nothing
+true
 ```
 """
 findlast(testf::Function, A) = findprev(testf, A, endof(A))

base/bitarray.jl

@@ -1459,13 +1459,13 @@ function unsafe_bitfindnext(Bc::Vector{UInt64}, start::Integer)
             end
         end
     end
-    return 0
+    return nothing
 end
 
-# returns the index of the next non-zero element, or 0 if all zeros
+# returns the index of the next true element, or nothing if all false
 function findnext(B::BitArray, start::Integer)
     start > 0 || throw(BoundsError(B, start))
-    start > length(B) && return 0
+    start > length(B) && return nothing
     unsafe_bitfindnext(B.chunks, start)
 end
 
@@ -1474,11 +1474,11 @@ end
 # aux function: same as findnext(~B, start), but performed without temporaries
 function findnextnot(B::BitArray, start::Integer)
     start > 0 || throw(BoundsError(B, start))
-    start > length(B) && return 0
+    start > length(B) && return nothing
 
     Bc = B.chunks
     l = length(Bc)
-    l == 0 && return 0
+    l == 0 && return nothing
 
     chunk_start = _div64(start-1)+1
     within_chunk_start = _mod64(start-1)
@@ -1499,15 +1499,16 @@ function findnextnot(B::BitArray, start::Integer)
     elseif Bc[l] | mask != _msk_end(B)
         return (l-1) << 6 + trailing_ones(Bc[l] | mask) + 1
     end
-    return 0
+    return nothing
 end
 findfirstnot(B::BitArray) = findnextnot(B,1)
 
 # returns the index of the first matching element
-function findnext(B::BitArray, v, start::Integer)
+function findnext(pred::EqualTo, B::BitArray, start::Integer)
+    v = pred.x
     v == false && return findnextnot(B, start)
     v == true && return findnext(B, start)
-    return 0
+    return nothing
 end
 #findfirst(B::BitArray, v) = findnext(B, 1, v)  ## defined in array.jl
 
@@ -1519,9 +1520,9 @@ function findnext(testf::Function, B::BitArray, start::Integer)
     f0 && !f1 && return findnextnot(B, start)
 
     start > 0 || throw(BoundsError(B, start))
-    start > length(B) && return 0
+    start > length(B) && return nothing
     f0 && f1 && return Int(start)
-    return 0 # last case: !f0 && !f1
+    return nothing # last case: !f0 && !f1
 end
 #findfirst(testf::Function, B::BitArray) = findnext(testf, B, 1)  ## defined in array.jl
 
@@ -1540,18 +1541,18 @@ function unsafe_bitfindprev(Bc::Vector{UInt64}, start::Integer)
             end
         end
     end
-    return 0
+    return nothing
 end
 
-# returns the index of the previous non-zero element, or 0 if all zeros
+# returns the index of the previous true element, or nothing if all false
 function findprev(B::BitArray, start::Integer)
-    start > 0 || return 0
+    start > 0 || return nothing
     start > length(B) && throw(BoundsError(B, start))
     unsafe_bitfindprev(B.chunks, start)
 end
 
 function findprevnot(B::BitArray, start::Integer)
-    start > 0 || return 0
+    start > 0 || return nothing
     start > length(B) && throw(BoundsError(B, start))
 
     Bc = B.chunks
@@ -1570,15 +1571,16 @@ function findprevnot(B::BitArray, start::Integer)
             end
         end
     end
-    return 0
+    return nothing
 end
 findlastnot(B::BitArray) = findprevnot(B, length(B))
 
 # returns the index of the previous matching element
-function findprev(B::BitArray, v, start::Integer)
+function findprev(pred::EqualTo, B::BitArray, start::Integer)
+    v = pred.x
     v == false && return findprevnot(B, start)
     v == true && return findprev(B, start)
-    return 0
+    return nothing
 end
 #findlast(B::BitArray, v) = findprev(B, 1, v)  ## defined in array.jl
 
@@ -1589,10 +1591,10 @@ function findprev(testf::Function, B::BitArray, start::Integer)
     !f0 && f1 && return findprev(B, start)
     f0 && !f1 && return findprevnot(B, start)
 
-    start > 0 || return 0
+    start > 0 || return nothing
     start > length(B) && throw(BoundsError(B, start))
     f0 && f1 && return Int(start)
-    return 0 # last case: !f0 && !f1
+    return nothing # last case: !f0 && !f1
 end
 #findlast(testf::Function, B::BitArray) = findprev(testf, B, 1)  ## defined in array.jl
 

base/bitset.jl

@@ -68,14 +68,16 @@ function _bits_findnext(b::Bits, start::Int)
     # start is 0-based
     # @assert start >= 0
     _div64(start) + 1 > length(b) && return -1
-    unsafe_bitfindnext(b, start+1) - 1
+    ind = unsafe_bitfindnext(b, start+1)
+    ind === nothing ? -1 : ind - 1
 end
 
 function _bits_findprev(b::Bits, start::Int)
     # start is 0-based
     # @assert start <= 64 * length(b) - 1
     start >= 0 || return -1
-    unsafe_bitfindprev(b, start+1) - 1
+    ind = unsafe_bitfindprev(b, start+1)
+    ind === nothing ? -1 : ind - 1
 end
 
 # An internal function for setting the inclusion bit for a given integer

base/client.jl

@@ -149,7 +149,7 @@ function display_error(io::IO, er, bt)
     print_with_color(Base.error_color(), io, "ERROR: "; bold = true)
     # remove REPL-related frames from interactive printing
     eval_ind = findlast(addr->Base.REPL.ip_matches_func(addr, :eval), bt)
-    if eval_ind != 0
+    if eval_ind !== nothing
         bt = bt[1:eval_ind-1]
     end
     showerror(IOContext(io, :limit => true), er, bt)

base/combinatorics.jl

@@ -75,7 +75,7 @@ function permute!!(a, p::AbstractVector{<:Integer})
     count = 0
     start = 0
     while count < length(a)
-        ptr = start = findnext(!iszero, p, start+1)
+        ptr = start = findnext(!iszero, p, start+1)::Int
         temp = a[start]
         next = p[start]
         count += 1
@@ -125,7 +125,7 @@ function invpermute!!(a, p::AbstractVector{<:Integer})
     count = 0
     start = 0
     while count < length(a)
-        start = findnext(!iszero, p, start+1)
+        start = findnext(!iszero, p, start+1)::Int
         temp = a[start]
         next = p[start]
         count += 1

base/event.jl

@@ -231,7 +231,7 @@ function ensure_rescheduled(othertask::Task)
         # also need to return it to the runnable state
         # before throwing an error
         i = findfirst(t->t===ct, Workqueue)
-        i == 0 || deleteat!(Workqueue, i)
+        i === nothing || deleteat!(Workqueue, i)
         ct.state = :runnable
     end
     nothing

base/file.jl

@@ -271,7 +271,7 @@ function tempname(temppath::AbstractString,uunique::UInt32)
     tempp = cwstring(temppath)
     tname = Vector{UInt16}(uninitialized, 32767)
     uunique = ccall(:GetTempFileNameW,stdcall,UInt32,(Ptr{UInt16},Ptr{UInt16},UInt32,Ptr{UInt16}), tempp,temp_prefix,uunique,tname)
-    lentname = findfirst(iszero,tname)-1
+    lentname = coalesce(findfirst(iszero,tname), 0)-1
     if uunique == 0 || lentname <= 0
         error("GetTempFileName failed: $(Libc.FormatMessage())")
     end

base/filesystem.jl

@@ -43,6 +43,7 @@ import Base:
     nb_available, position, read, read!, readavailable, seek, seekend, show,
     skip, stat, unsafe_read, unsafe_write, transcode, uv_error, uvhandle,
     uvtype, write
+using Base: coalesce
 
 if Sys.iswindows()
     import Base: cwstring

base/inference.jl

@@ -1822,7 +1822,7 @@ function builtin_tfunction(@nospecialize(f), argtypes::Array{Any,1},
         tf = t_ifunc[iidx]
     else
         fidx = findfirst(x->x===f, t_ffunc_key)
-        if fidx == 0
+        if fidx === nothing
             # unknown/unhandled builtin function
             return Any
         end
@@ -5147,7 +5147,7 @@ function statement_cost(ex::Expr, line::Int, src::CodeInfo, mod::Module, params:
                     return plus_saturate(argcost, isknowntype(ex.typ) ? 4 : params.inline_nonleaf_penalty)
                 end
                 fidx = findfirst(x->x===f, t_ffunc_key)
-                if fidx == 0
+                if fidx === nothing
                     # unknown/unhandled builtin or anonymous function
                     # Use the generic cost of a direct function call
                     return plus_saturate(argcost, 20)