Impl, docs, & tests for searchsortedbefore

Author: devinallen

docs/src/sorted_containers.md

@@ -140,6 +140,7 @@ regress(token::Token)
 Base.searchsortedfirst(m::SortedContainer, k)
 Base.searchsortedlast(m::SortedContainer, k)
 searchsortedafter(m::SortedContainer, k)
+searchsortedbefore(m::SortedContainer, k)
 searchequalrange(smd::SortedMultiDict, k)
 findkey(m::SortedSet, k)
 findkey(sd::SortedDict, k)

src/DataStructures.jl

@@ -37,7 +37,7 @@ module DataStructures
     export SetSemiToken
     export pastendsemitoken, beforestartsemitoken
     export pastendtoken, beforestarttoken
-    export searchsortedafter, searchequalrange
+    export searchsortedafter, searchsortedbefore, searchequalrange
     export packcopy, packdeepcopy
     export exclusive, inclusive, semitokens, inclusive_key, exclusive_key
     export orderobject, ordtype, Lt, compare, onlysemitokens

src/sorted_container_iteration.jl

@@ -455,6 +455,19 @@ function Base.searchsortedlast(m::SortedContainer, k_)
 end
 
 
+"""
+    searchsortedbefore(m::SortedContainer, k)
+
+Return the semitoken of the last item in the container that is less than
+`k` in the sort order.  If there is no
+such item, then the before-start semitoken is returned.  Time: O(*c* log *n*)
+"""
+function searchsortedbefore(m::SortedContainer, k_)
+    i = findkeyless(m.bt, convert(keytype(m), k_))
+    IntSemiToken(i)
+end
+
+
 ## The next four are correctness-checking routines.  They are
 ## not exported.
 

test/test_sorted_containers.jl

@@ -485,6 +485,10 @@ function testSortedDictMethods()
     i17 = searchsortedlast(m1, 48)
     my_assert(deref_key((m1,i16)) == 47)
     my_assert(deref_key((m1,i17)) == 47)
+    i16 = searchsortedbefore(m1, 47)
+    i17 = searchsortedbefore(m1, 48)
+    my_assert(deref_key((m1,i16)) == 43)
+    my_assert(deref_key((m1,i17)) == 47)
     ww = my_primes(N)
     cc = last(m1)
     my_assert(cc[1] == last(ww))
@@ -1337,6 +1341,8 @@ function testSortedMultiDict()
     my_assert(deref((factors,i)) == Pair(77,77))
     i = searchsortedafter(factors,77)
     my_assert(deref((factors,i)) == Pair(78,1))
+    i = searchsortedbefore(factors,77)
+    my_assert(deref((factors,i)) == Pair(76,76))
     expected = [1,2,4,5,8,10,16,20,40,80]
     i1,i2 = searchequalrange(factors, 80)
     i = i1
@@ -1613,16 +1619,21 @@ function testSortedSet()
     j1 = searchsortedfirst(m,0.5)
     j2 = searchsortedlast(m,0.5)
     j3 = searchsortedafter(m,0.5)
+    j4 = searchsortedbefore(m,0.5)
     my_assert(deref((m,j1)) > 0.5)
     my_assert(deref((m,j2)) < 0.5)
     my_assert(advance((m,j2)) == j1)
     my_assert(j1 == j3)
+    my_assert(j2 == j4)
     k1 = searchsortedfirst(m,smallest)
     k2 = searchsortedlast(m,smallest)
     k3 = searchsortedafter(m,smallest)
+    k4 = searchsortedbefore(m,smallest)
     my_assert(deref((m,k1)) == smallest)
     my_assert(deref((m,k2)) == smallest)
     my_assert(deref((m,regress((m,k3)))) == smallest)
+    my_assert(deref((m,advance((m,k4)))) == smallest)
+    my_assert(k4 == beforestartsemitoken(m))
     secondsmallest = deref((m,k3))
     sk = searchsortedfirst(m,0.4)
     ek = searchsortedfirst(m,0.6)