Merge pull request #18339 from TotalVerb/fw/split

Make `chop` and `chomp` return `SubString`

Author: StefanKarpinski

base/strings/util.jl

@@ -58,21 +58,20 @@ startswith(a::Vector{UInt8}, b::Vector{UInt8}) =
 
 # TODO: fast endswith
 
-
 """
     chop(s::AbstractString)
 
 Remove the last character from `s`.
 
 ```jldoctest
-julia> a = string("March")
+julia> a = "March"
 "March"
 
 julia> chop(a)
 "Marc"
 ```
 """
-chop(s::AbstractString) = s[1:end-1]
+chop(s::AbstractString) = SubString(s, 1, endof(s)-1)
 
 """
     chomp(s::AbstractString)
@@ -81,14 +80,21 @@ Remove a single trailing newline from a string.
 """
 function chomp(s::AbstractString)
     i = endof(s)
-    if (i < 1 || s[i] != '\n') return s end
+    if (i < 1 || s[i] != '\n') return SubString(s, 1, i) end
     j = prevind(s,i)
-    if (j < 1 || s[j] != '\r') return s[1:i-1] end
-    return s[1:j-1]
+    if (j < 1 || s[j] != '\r') return SubString(s, 1, i-1) end
+    return SubString(s, 1, j-1)
+end
+function chomp(s::String)
+    i = endof(s)
+    if i < 1 || s.data[i] != 0x0a
+        SubString(s, 1, i)
+    elseif i < 2 || s.data[i-1] != 0x0d
+        SubString(s, 1, i-1)
+    else
+        SubString(s, 1, i-2)
+    end
 end
-chomp(s::String) =
-    (endof(s) < 1 || s.data[end]   != 0x0a) ? s :
-    (endof(s) < 2 || s.data[end-1] != 0x0d) ? s[1:end-1] : s[1:end-2]
 
 # NOTE: use with caution -- breaks the immutable string convention!
 function chomp!(s::String)

doc/stdlib/strings.rst

@@ -450,7 +450,7 @@
 
    .. doctest::
 
-       julia> a = string("March")
+       julia> a = "March"
        "March"
 
        julia> chop(a)

test/strings/util.jl

@@ -210,7 +210,9 @@ end
 
 # chomp/chop
 @test chomp("foo\n") == "foo"
-@test chop("foob") == "foo"
+@test chop("fooε") == "foo"
+@test isa(chomp("foo"), SubString)
+@test isa(chop("foo"), SubString)
 
 # bytes2hex and hex2bytes
 hex_str = "d7a8fbb307d7809469ca9abcb0082e4f8d5651e46d3cdb762d02d0bf37c9e592"