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Work String#starts_with? with regex #5485

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Apr 9, 2018
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Work String#starts_with? with regex #5485

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b6bd2dc
Work String#starts_with? with regex
makenowjust Dec 30, 2017
8432c14
Fix String#ends_with to accept regex
makenowjust Jan 2, 2018
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4 changes: 4 additions & 0 deletions spec/std/string_spec.cr
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Original file line number Diff line number Diff line change
Expand Up @@ -925,6 +925,8 @@ describe "String" do
it { "foobar".starts_with?("").should be_true }
it { "foobar".starts_with?("foobarbaz").should be_false }
it { "foobar".starts_with?("foox").should be_false }
it { "foobar".starts_with?(/foo/).should be_true }
it { "foobar".starts_with?(/bar/).should be_false }
it { "foobar".starts_with?('f').should be_true }
it { "foobar".starts_with?('g').should be_false }
it { "よし".starts_with?('よ').should be_true }
Expand All @@ -936,6 +938,8 @@ describe "String" do
it { "foobar".ends_with?("").should be_true }
it { "foobar".ends_with?("foobarbaz").should be_false }
it { "foobar".ends_with?("xbar").should be_false }
it { "foobar".ends_with?(/bar/).should be_true }
it { "foobar".ends_with?(/foo|baz/).should be_false }
it { "foobar".ends_with?('r').should be_true }
it { "foobar".ends_with?('x').should be_false }
it { "よし".ends_with?('し').should be_true }
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8 changes: 8 additions & 0 deletions src/string.cr
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Expand Up @@ -3969,6 +3969,10 @@ class String
false
end

def starts_with?(re : Regex)
!!($~ = re.match_at_byte_index(self, 0, Regex::Options::ANCHORED))
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That's a fairly confusing definition, how about:

def starts_with?(re : Regex)
  match_data = $~ = re.match_at_byte_index(self, 0, Regex::Options::ANCHORED)

  match_data != nil
end

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@makenowjust makenowjust Dec 30, 2017 •
edited
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Your code has another confusability. It seems match_data is redundant and last statement can be replaced with $~ != nil, unfortunately it cannot. It is hard to explain this reason, so I cannot accept your suggestion. Please approve.

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I disagree.

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Why?

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I just think that this way is easier to understand. Perhaps:

match_data = re.match_at_byte_index(self, 0, Regex::Options::ANCHORED)

$~ = match_data
match_data != nil

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This is such a small method that I think the original code is fine.

end

def ends_with?(str : String)
return false if str.bytesize > bytesize
(to_unsafe + bytesize - str.bytesize).memcmp(str.to_unsafe, str.bytesize) == 0
Expand All @@ -3991,6 +3995,10 @@ class String
true
end

def ends_with?(re : Regex)
!!($~ = /#{re}\z/.match(self))
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Doesn't this require /(?:#{re})\z/?

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Needless, re.to_s yields enclosed string.

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Oh, cool.

end

# Interpolates *other* into the string using `Kernel#sprintf`.
#
# ```
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