From: Hideto ISHIBASHI <hideto-i@...4u.or.jp>
Date: 2000-04-22T19:49:50+09:00
Subject: [ruby-list:22066] Re: assert

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石橋秀仁です。

> 友谷です。

> で、assertを組み込むのであればこんなのはどうでしょうか。

ちょっと脱線します。
厳密にはassertではないのですが、次のようなものはどうでしょう？
実行時にエラーの回復をするためのライブラリです。

--
Hideto "rubyholic" ISHIBASHI


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module Assert

  class AssertionError < StandardError; end

  def assert(*args, &block)
    return nil unless $DEBUG
    __assert__(*args, &block)
  end

  def __assert__(*args)
    return true if yield == true
    msg = "assertion failed:"
    for arg in args
      msg += " " + arg.inspect
    end
    raise AssertionError, msg
  end

  def recoverable_assert(*args, &block)
    return nil unless $DEBUG
    assert_and_recovery(*args, &block)
  end

  def assert_and_recovery(*args, &block)
    begin
      return true if __assert__(*args, &block)
    rescue
      exception = $!
      STDOUT.print exception, "\n"
      for c in caller(0)
        STDOUT.print c, "\n"
      end
    end
    STDOUT.print "type 'help' to display help message.\n"

    loop do
      input = readline("(recovery:-) ")
      case input
      when /^\s*h(?:elp)?\s*$/
	STDOUT.print <<EOS
help	print this message
fail	raise AssertionError
local	print local variables
retry	retry assertion
...	eval an input string
EOS
      when /^\s*f(?:ail)?\s*$/
	fail exception
      when /^\s*l(?:ocal)?\s*$/
        STDOUT.print "local variables (name : type = value)\n"
	eval(<<-EOE, block)
          for lv in local_variables - ["lv"]
            STDOUT.print " ", lv, "\t: ", lv.type, "\t= ", eval(lv), "\n"
          end
	EOE
      when /^\s*r(?:etry)?\s*$/
        begin
          return true if __assert__(*args, &block)
        rescue
          STDOUT.print $!, "\n"
        end
      else
	begin
          STDOUT.print eval(input, block).inspect, "\n"
	rescue
	  STDOUT.print $!, "\n"
	end
      end
    end
  end

  def readline(prompt)
    STDOUT.print prompt
    STDOUT.flush
    line = STDIN.gets
    line.chomp!
    line
  end
end

if __FILE__ == $0

  include Assert

  orig = "This is a pen."
  pen = orig.dup
  str = pen

  assert("pen == orig ?") {pen == orig}
  str.sub!(/a/, "A")
  recoverable_assert("pen == orig ?") {pen == orig}
  #assert_and_recovery("pen == orig ?") {pen == orig}

  print "recoverd.\n"

end

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$ ruby assert.rb 
recoverd.
$ ruby -d assert.rb 
Exception `Assert::AssertionError' at assert.rb:16
assertion failed: "pen == orig ?"
assert.rb:30:in `assert_and_recovery'
assert.rb:21:in `recoverable_assert'
assert.rb:91
type 'help' to display help message.
(recovery:-) help
help	print this message
fail	raise AssertionError
local	print local variables
retry	retry assertion
...	eval an input string
(recovery:-) l
local variables (name : type = value)
 orig	: String	= This is a pen.
 pen	: String	= This is A pen.
 str	: String	= This is A pen.
(recovery:-) r
Exception `Assert::AssertionError' at assert.rb:16
assertion failed: "pen == orig ?"
(recovery:-) pen.sub!(/A/, "a")
"This is a pen."
(recovery:-) l
local variables (name : type = value)
 orig	: String	= This is a pen.
 pen	: String	= This is a pen.
 str	: String	= This is a pen.
(recovery:-) orig
"This is a pen."
(recovery:-) retry
recoverd.
$ ruby -d assert.rb 
Exception `Assert::AssertionError' at assert.rb:16
assertion failed: "pen == orig ?"
assert.rb:30:in `assert_and_recovery'
assert.rb:21:in `recoverable_assert'
assert.rb:91
type 'help' to display help message.
(recovery:-) r
Exception `Assert::AssertionError' at assert.rb:16
assertion failed: "pen == orig ?"
(recovery:-) f
Exception `Assert::AssertionError' at assert.rb:48
assert.rb:48:in `assert_and_recovery': assertion failed: "pen == orig ?" (Assert::AssertionError)
	from assert.rb:37:in `loop'
	from assert.rb:37:in `assert_and_recovery'
	from assert.rb:21:in `recoverable_assert'
	from assert.rb:91
$ 
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