require explicit predicates in find functions

fix #23120, fix #19186

Author: JeffBezanson

NEWS.md

@@ -292,6 +292,9 @@ Library improvements
 
   * REPL Undo via Ctrl-/ and Ctrl-_
 
+  * New function `equalto(x)`, which returns a function that compares its argument to `x`
+    using `isequal` ([#23812]).
+
 Compiler/Runtime improvements
 -----------------------------
 
@@ -484,6 +487,12 @@ Deprecated or removed
   * The timing functions `tic`, `toc`, and `toq` are deprecated in favor of `@time` and `@elapsed`
     ([#17046]).
 
+  * Methods of `findfirst`, `findnext`, `findlast`, and `findprev` that accept a value to
+    search for are deprecated in favor of passing a predicate ([#19186], [#10593]).
+
+  * `find` functions now operate only on booleans by default. To look for non-zeros, use
+    `x->x!=0` or `!iszero` ([#23120]).
+
 Command-line option changes
 ---------------------------
 

base/array.jl

@@ -1599,14 +1599,14 @@ 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 non-zero element of `A`, or `0` if not found.
+Find the next linear index >= `i` of a `true` element of `A`, or `0` if not found.
 
 # Examples
 ```jldoctest
-julia> A = [0 0; 1 0]
-2×2 Array{Int64,2}:
- 0  0
- 1  0
+julia> A = [false false; true false]
+2×2 Array{Bool,2}:
+ false  false
+  true  false
 
 julia> findnext(A,1)
 2
@@ -1618,8 +1618,14 @@ julia> findnext(A,3)
 function findnext(A, start::Integer)
     l = endof(A)
     i = start
+    warned = false
     while i <= l
-        if A[i] != 0
+        a = A[i]
+        if !warned && !(a isa Bool)
+            depwarn("In the future `findnext` will only work on boolean collections. Use `findnext(x->x!=0, A)` instead.", :findnext)
+            warned = true
+        end
+        if a != 0
             return i
         end
         i = nextind(A, i)
@@ -1630,8 +1636,9 @@ end
 """
     findfirst(A)
 
-Return the linear index of the first non-zero value in `A` (determined by `A[i]!=0`).
+Return the linear index of the first `true` value in `A`.
 Returns `0` if no such value is found.
+To search for other kinds of values, pass a predicate as the first argument.
 
 # Examples
 ```jldoctest
@@ -1649,58 +1656,6 @@ julia> findfirst(zeros(3))
 """
 findfirst(A) = findnext(A, 1)
 
-"""
-    findnext(A, v, i::Integer)
-
-Find the next linear index >= `i` of an element of `A` equal to `v` (using `==`), or `0` if not found.
-
-# Examples
-```jldoctest
-julia> A = [1 4; 2 2]
-2×2 Array{Int64,2}:
- 1  4
- 2  2
-
-julia> findnext(A,4,4)
-0
-
-julia> findnext(A,4,3)
-3
-```
-"""
-function findnext(A, v, start::Integer)
-    l = endof(A)
-    i = start
-    while i <= l
-        if A[i] == v
-            return i
-        end
-        i = nextind(A, i)
-    end
-    return 0
-end
-"""
-    findfirst(A, v)
-
-Return the linear index of the first element equal to `v` in `A`.
-Returns `0` if `v` is not found.
-
-# Examples
-```jldoctest
-julia> A = [4 6; 2 2]
-2×2 Array{Int64,2}:
- 4  6
- 2  2
-
-julia> findfirst(A,2)
-2
-
-julia> findfirst(A,3)
-0
-```
-"""
-findfirst(A, v) = findnext(A, v, 1)
-
 """
     findnext(predicate::Function, A, i::Integer)
 
@@ -1750,21 +1705,24 @@ julia> findfirst(iseven, A)
 
 julia> findfirst(x -> x>10, A)
 0
+
+julia> findfirst(equalto(4), A)
+3
 ```
 """
 findfirst(testf::Function, A) = findnext(testf, A, 1)
 
 """
     findprev(A, i::Integer)
 
-Find the previous linear index <= `i` of a non-zero element of `A`, or `0` if not found.
+Find the previous linear index <= `i` of a `true` element of `A`, or `0` if not found.
 
 # Examples
 ```jldoctest
-julia> A = [0 0; 1 2]
-2×2 Array{Int64,2}:
- 0  0
- 1  2
+julia> A = [false false; true true]
+2×2 Array{Bool,2}:
+ false  false
+  true  true
 
 julia> findprev(A,2)
 2
@@ -1775,8 +1733,14 @@ julia> findprev(A,1)
 """
 function findprev(A, start::Integer)
     i = start
+    warned = false
     while i >= 1
-        A[i] != 0 && return i
+        a = A[i]
+        if !warned && !(a isa Bool)
+            depwarn("In the future `findprev` will only work on boolean collections. Use `findprev(x->x!=0, A)` instead.", :findprev)
+            warned = true
+        end
+        a != 0 && return i
         i = prevind(A, i)
     end
     return 0
@@ -1785,8 +1749,8 @@ end
 """
     findlast(A)
 
-Return the linear index of the last non-zero value in `A` (determined by `A[i]!=0`).
-Returns `0` if there is no non-zero value in `A`.
+Return the linear index of the last `true` value in `A`.
+Returns `0` if there is no `true` value in `A`.
 
 # Examples
 ```jldoctest
@@ -1809,59 +1773,6 @@ julia> findlast(A)
 """
 findlast(A) = findprev(A, endof(A))
 
-"""
-    findprev(A, v, i::Integer)
-
-Find the previous linear index <= `i` of an element of `A` equal to `v` (using `==`), or `0` if not found.
-
-# Examples
-```jldoctest
-julia> A = [0 0; 1 2]
-2×2 Array{Int64,2}:
- 0  0
- 1  2
-
-julia> findprev(A, 1, 4)
-2
-
-julia> findprev(A, 1, 1)
-0
-```
-"""
-function findprev(A, v, start::Integer)
-    i = start
-    while i >= 1
-        A[i] == v && return i
-        i = prevind(A, i)
-    end
-    return 0
-end
-
-"""
-    findlast(A, v)
-
-Return the linear index of the last element equal to `v` in `A`.
-Returns `0` if there is no element of `A` equal to `v`.
-
-# Examples
-```jldoctest
-julia> A = [1 2; 2 1]
-2×2 Array{Int64,2}:
- 1  2
- 2  1
-
-julia> findlast(A,1)
-4
-
-julia> findlast(A,2)
-3
-
-julia> findlast(A,3)
-0
-```
-"""
-findlast(A, v) = findprev(A, v, endof(A))
-
 """
     findprev(predicate::Function, A, i::Integer)
 
@@ -1921,16 +1832,23 @@ If there are no such elements of `A`, find returns an empty array.
 
 # Examples
 ```jldoctest
-julia> A = [1 2; 3 4]
-2×2 Array{Int64,2}:
- 1  2
- 3  4
+julia> A = [1 2 0; 3 4 0]
+2×3 Array{Int64,2}:
+ 1  2  0
+ 3  4  0
 
-julia> find(isodd,A)
+julia> find(isodd, A)
 2-element Array{Int64,1}:
  1
  2
 
+julia> find(!iszero, A)
+4-element Array{Int64,1}:
+ 1
+ 2
+ 3
+ 4
+
 julia> find(isodd, [2, 4])
 0-element Array{Int64,1}
 ```
@@ -1955,9 +1873,8 @@ _index_remapper(iter) = OneTo(typemax(Int))  # safe for objects that don't imple
 """
     find(A)
 
-Return a vector of the linear indexes of the non-zeros in `A` (determined by `A[i]!=0`). A
-common use of this is to convert a boolean array to an array of indexes of the `true`
-elements. If there are no non-zero elements of `A`, `find` returns an empty array.
+Return a vector of the linear indices of the `true` values in `A`.
+To search for other kinds of values, pass a predicate as the first argument.
 
 # Examples
 ```jldoctest
@@ -1971,7 +1888,7 @@ julia> find(A)
  1
  4
 
-julia> find(zeros(3))
+julia> find(falses(3))
 0-element Array{Int64,1}
 ```
 """
@@ -1980,7 +1897,12 @@ function find(A)
     I = Vector{Int}(nnzA)
     cnt = 1
     inds = _index_remapper(A)
+    warned = false
     for (i,a) in enumerate(A)
+        if !warned && !(a isa Bool)
+            depwarn("In the future `find(A)` will only work on boolean collections. Use `find(x->x!=0, A)` instead.", :find)
+            warned = true
+        end
         if a != 0
             I[cnt] = inds[i]
             cnt += 1
@@ -1989,7 +1911,7 @@ function find(A)
     return I
 end
 
-find(x::Number) = x == 0 ? Array{Int,1}(0) : [1]
+find(x::Bool) = x ? [1] : Array{Int,1}(0)
 find(testf::Function, x::Number) = !testf(x) ? Array{Int,1}(0) : [1]
 
 findn(A::AbstractVector) = find(A)

base/combinatorics.jl

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

base/datafmt.jl

@@ -370,7 +370,7 @@ function val_opts(opts)
     for (opt_name, opt_val) in opts
         in(opt_name, valid_opts) ||
             throw(ArgumentError("unknown option $opt_name"))
-        opt_typ = valid_opt_types[findfirst(valid_opts, opt_name)]
+        opt_typ = valid_opt_types[findfirst(equalto(opt_name), valid_opts)]
         isa(opt_val, opt_typ) ||
             throw(ArgumentError("$opt_name should be of type $opt_typ, got $(typeof(opt_val))"))
         d[opt_name] = opt_val

base/deprecated.jl

@@ -1918,6 +1918,14 @@ end
 @deprecate strwidth textwidth
 @deprecate charwidth textwidth
 
+@deprecate find(x::Number)            find(!iszero, x)
+@deprecate findnext(A, v, i::Integer) findnext(equalto(v), A, i)
+@deprecate findfirst(A, v)            findfirst(equalto(v), A)
+@deprecate findprev(A, v, i::Integer) findprev(equalto(v), A, i)
+@deprecate findlast(A, v)             findlast(equalto(v), A)
+# also remove deprecation warnings in find* functions in array.jl, sparse/sparsematrix.jl,
+# and sparse/sparsevector.jl.
+
 # END 0.7 deprecations
 
 # BEGIN 1.0 deprecations

base/event.jl

@@ -234,7 +234,7 @@ function ensure_rescheduled(othertask::Task)
         # if the current task was queued,
         # also need to return it to the runnable state
         # before throwing an error
-        i = findfirst(Workqueue, ct)
+        i = findfirst(t->t===ct, Workqueue)
         i == 0 || deleteat!(Workqueue, i)
         ct.state = :runnable
     end

base/exports.jl

@@ -859,6 +859,7 @@ export
     identity,
     isbits,
     isequal,
+    equalto,
     isimmutable,
     isless,
     ifelse,

base/file.jl

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