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add rand(::String) #22224

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merged 7 commits into from
Jun 15, 2017
Merged

add rand(::String) #22224

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459a126
add rand(::String)
rfourquet May 31, 2017
1deb0c5
test for empty strings (StefanKarpinski) and fix bad usage a GLOBAL_RNG
rfourquet Jun 5, 2017
5e827e9
warn about linear complexity for AbstractString (stevengj)
rfourquet Jun 6, 2017
533dfb3
use O(1) algo for generic AbstractString (StefanKarpinski)
rfourquet Jun 7, 2017
3b97b61
use isvalid instead of try/catch in generic implementation (StefanKar…
rfourquet Jun 13, 2017
fa51ee6
add a missing "or" in doc (stevengj)
rfourquet Jun 13, 2017
a5289a1
add NEWS.md entry
rfourquet Jun 14, 2017
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use isvalid instead of try/catch in generic implementation (StefanKar… 
…pinski)
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@rfourquet
rfourquet committed Jun 13, 2017
commit 3b97b615b46c27487ab53d25b7d15c84980a33bf
16 changes: 5 additions & 11 deletions base/random.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -713,24 +713,18 @@ rand(rng::AbstractRNG, r::AbstractArray, dims::Integer...) = rand(rng, r, conver
# rand from a string

isvalid_unsafe(s::String, i) = !Base.is_valid_continuation(unsafe_load(pointer(s), i))
isvalid_unsafe(s::AbstractString, i) = isvalid(s, i)
_endof(s::String) = s.len
_endof(s::AbstractString) = endof(s)

function rand(rng::AbstractRNG, s::String)::Char
g = RangeGenerator(1:s.len)
function rand(rng::AbstractRNG, s::AbstractString)::Char
g = RangeGenerator(1:_endof(s))
while true
pos = rand(rng, g)
isvalid_unsafe(s, pos) && return s[pos]
end
end

function rand(rng::AbstractRNG, s::AbstractString)::Char
g = RangeGenerator(1:endof(s))
while true
try # the generic `isvalid` includes an equivalent try/catch statement
return s[rand(rng, g)]
end
end
end

rand(s::AbstractString) = rand(GLOBAL_RNG, s)

## rand from a string for arrays
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