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Diffstat (limited to 'ruby_1_9_3/lib/prettyprint.rb')
| -rw-r--r-- | ruby_1_9_3/lib/prettyprint.rb | 395 |
1 files changed, 395 insertions, 0 deletions
diff --git a/ruby_1_9_3/lib/prettyprint.rb b/ruby_1_9_3/lib/prettyprint.rb new file mode 100644 index 0000000000..9a90713a4d --- /dev/null +++ b/ruby_1_9_3/lib/prettyprint.rb @@ -0,0 +1,395 @@ +# This class implements a pretty printing algorithm. It finds line breaks and +# nice indentations for grouped structure. +# +# By default, the class assumes that primitive elements are strings and each +# byte in the strings have single column in width. But it can be used for +# other situations by giving suitable arguments for some methods: +# * newline object and space generation block for PrettyPrint.new +# * optional width argument for PrettyPrint#text +# * PrettyPrint#breakable +# +# There are several candidate uses: +# * text formatting using proportional fonts +# * multibyte characters which has columns different to number of bytes +# * non-string formatting +# +# == Bugs +# * Box based formatting? +# * Other (better) model/algorithm? +# +# == References +# Christian Lindig, Strictly Pretty, March 2000, +# http://www.st.cs.uni-sb.de/~lindig/papers/#pretty +# +# Philip Wadler, A prettier printer, March 1998, +# http://homepages.inf.ed.ac.uk/wadler/topics/language-design.html#prettier +# +# == Author +# Tanaka Akira <akr@m17n.org> +# +class PrettyPrint + + # This is a convenience method which is same as follows: + # + # begin + # q = PrettyPrint.new(output, maxwidth, newline, &genspace) + # ... + # q.flush + # output + # end + # + def PrettyPrint.format(output='', maxwidth=79, newline="\n", genspace=lambda {|n| ' ' * n}) + q = PrettyPrint.new(output, maxwidth, newline, &genspace) + yield q + q.flush + output + end + + # This is similar to PrettyPrint::format but the result has no breaks. + # + # +maxwidth+, +newline+ and +genspace+ are ignored. + # + # The invocation of +breakable+ in the block doesn't break a line and is + # treated as just an invocation of +text+. + # + def PrettyPrint.singleline_format(output='', maxwidth=nil, newline=nil, genspace=nil) + q = SingleLine.new(output) + yield q + output + end + + # Creates a buffer for pretty printing. + # + # +output+ is an output target. If it is not specified, '' is assumed. It + # should have a << method which accepts the first argument +obj+ of + # PrettyPrint#text, the first argument +sep+ of PrettyPrint#breakable, the + # first argument +newline+ of PrettyPrint.new, and the result of a given + # block for PrettyPrint.new. + # + # +maxwidth+ specifies maximum line length. If it is not specified, 79 is + # assumed. However actual outputs may overflow +maxwidth+ if long + # non-breakable texts are provided. + # + # +newline+ is used for line breaks. "\n" is used if it is not specified. + # + # The block is used to generate spaces. {|width| ' ' * width} is used if it + # is not given. + # + def initialize(output='', maxwidth=79, newline="\n", &genspace) + @output = output + @maxwidth = maxwidth + @newline = newline + @genspace = genspace || lambda {|n| ' ' * n} + + @output_width = 0 + @buffer_width = 0 + @buffer = [] + + root_group = Group.new(0) + @group_stack = [root_group] + @group_queue = GroupQueue.new(root_group) + @indent = 0 + end + attr_reader :output, :maxwidth, :newline, :genspace + attr_reader :indent, :group_queue + + # Returns the group most recently added to the stack. + def current_group + @group_stack.last + end + + # first? is a predicate to test the call is a first call to first? with + # current group. + # + # It is useful to format comma separated values as: + # + # q.group(1, '[', ']') { + # xxx.each {|yyy| + # unless q.first? + # q.text ',' + # q.breakable + # end + # ... pretty printing yyy ... + # } + # } + # + # first? is obsoleted in 1.8.2. + # + def first? + warn "PrettyPrint#first? is obsoleted at 1.8.2." + current_group.first? + end + + # Breaks the buffer into lines that are shorter than #maxwidth + def break_outmost_groups + while @maxwidth < @output_width + @buffer_width + return unless group = @group_queue.deq + until group.breakables.empty? + data = @buffer.shift + @output_width = data.output(@output, @output_width) + @buffer_width -= data.width + end + while !@buffer.empty? && Text === @buffer.first + text = @buffer.shift + @output_width = text.output(@output, @output_width) + @buffer_width -= text.width + end + end + end + + # This adds +obj+ as a text of +width+ columns in width. + # + # If +width+ is not specified, obj.length is used. + # + def text(obj, width=obj.length) + if @buffer.empty? + @output << obj + @output_width += width + else + text = @buffer.last + unless Text === text + text = Text.new + @buffer << text + end + text.add(obj, width) + @buffer_width += width + break_outmost_groups + end + end + + # This is similar to #breakable except + # the decision to break or not is determined individually. + # + # Two #fill_breakable under a group may cause 4 results: + # (break,break), (break,non-break), (non-break,break), (non-break,non-break). + # This is different to #breakable because two #breakable under a group + # may cause 2 results: + # (break,break), (non-break,non-break). + # + # The text sep+ is inserted if a line is not broken at this point. + # + # If +sep+ is not specified, " " is used. + # + # If +width+ is not specified, +sep.length+ is used. You will have to + # specify this when +sep+ is a multibyte character, for example. + # + def fill_breakable(sep=' ', width=sep.length) + group { breakable sep, width } + end + + # This says "you can break a line here if necessary", and a +width+\-column + # text +sep+ is inserted if a line is not broken at the point. + # + # If +sep+ is not specified, " " is used. + # + # If +width+ is not specified, +sep.length+ is used. You will have to + # specify this when +sep+ is a multibyte character, for example. + # + def breakable(sep=' ', width=sep.length) + group = @group_stack.last + if group.break? + flush + @output << @newline + @output << @genspace.call(@indent) + @output_width = @indent + @buffer_width = 0 + else + @buffer << Breakable.new(sep, width, self) + @buffer_width += width + break_outmost_groups + end + end + + # Groups line break hints added in the block. The line break hints are all + # to be used or not. + # + # If +indent+ is specified, the method call is regarded as nested by + # nest(indent) { ... }. + # + # If +open_obj+ is specified, <tt>text open_obj, open_width</tt> is called + # before grouping. If +close_obj+ is specified, <tt>text close_obj, + # close_width</tt> is called after grouping. + # + def group(indent=0, open_obj='', close_obj='', open_width=open_obj.length, close_width=close_obj.length) + text open_obj, open_width + group_sub { + nest(indent) { + yield + } + } + text close_obj, close_width + end + + def group_sub + group = Group.new(@group_stack.last.depth + 1) + @group_stack.push group + @group_queue.enq group + begin + yield + ensure + @group_stack.pop + if group.breakables.empty? + @group_queue.delete group + end + end + end + + # Increases left margin after newline with +indent+ for line breaks added in + # the block. + # + def nest(indent) + @indent += indent + begin + yield + ensure + @indent -= indent + end + end + + # outputs buffered data. + # + def flush + @buffer.each {|data| + @output_width = data.output(@output, @output_width) + } + @buffer.clear + @buffer_width = 0 + end + + class Text + def initialize + @objs = [] + @width = 0 + end + attr_reader :width + + def output(out, output_width) + @objs.each {|obj| out << obj} + output_width + @width + end + + def add(obj, width) + @objs << obj + @width += width + end + end + + class Breakable + def initialize(sep, width, q) + @obj = sep + @width = width + @pp = q + @indent = q.indent + @group = q.current_group + @group.breakables.push self + end + attr_reader :obj, :width, :indent + + def output(out, output_width) + @group.breakables.shift + if @group.break? + out << @pp.newline + out << @pp.genspace.call(@indent) + @indent + else + @pp.group_queue.delete @group if @group.breakables.empty? + out << @obj + output_width + @width + end + end + end + + class Group + def initialize(depth) + @depth = depth + @breakables = [] + @break = false + end + attr_reader :depth, :breakables + + def break + @break = true + end + + def break? + @break + end + + def first? + if defined? @first + false + else + @first = false + true + end + end + end + + class GroupQueue + def initialize(*groups) + @queue = [] + groups.each {|g| enq g} + end + + def enq(group) + depth = group.depth + @queue << [] until depth < @queue.length + @queue[depth] << group + end + + def deq + @queue.each {|gs| + (gs.length-1).downto(0) {|i| + unless gs[i].breakables.empty? + group = gs.slice!(i, 1).first + group.break + return group + end + } + gs.each {|group| group.break} + gs.clear + } + return nil + end + + def delete(group) + @queue[group.depth].delete(group) + end + end + + class SingleLine + def initialize(output, maxwidth=nil, newline=nil) + @output = output + @first = [true] + end + + def text(obj, width=nil) + @output << obj + end + + def breakable(sep=' ', width=nil) + @output << sep + end + + def nest(indent) + yield + end + + def group(indent=nil, open_obj='', close_obj='', open_width=nil, close_width=nil) + @first.push true + @output << open_obj + yield + @output << close_obj + @first.pop + end + + def flush + end + + def first? + result = @first[-1] + @first[-1] = false + result + end + end +end |