From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2001-10-30T09:51:10+09:00
Subject: [ruby-talk:23788] Re: Simple templating system (fixed - I hope:)

In article <i44D7.34286$TF4.1812047@sjcpnn01.usenetserver.com>,
Phil Tomson <ptkwt@shell1.aracnet.com> wrote:
>
>I'll fix these bugs and repost... maybe I'll put it on the RAA or 
>cookbook.

Here's the updated code with some bug fixes:

class String
  def interpolate(bind)
    eval (self.inspect,bind)
  end
end

class TemplateFile
   def initialize(file,bind)
      @file = file
      @bind = bind
      @stateArray = Array.new
      @stateArray << true #default read state
   end
   
   def interpolate(b = @bind)
      fileString = "" 
      File.foreach(@file) {|line|
        case line.strip
           when /^#>IF/
              #check condition
              expression = line.gsub(/#>IF/,"").strip
              condition = expression.interpolate(b)
              if condition.type == String
                 condition = eval condition
              end
              unless(condition.type == TrueClass || condition.type == 
FalseClass)
                 raise TypeError, "#>IF #{expression} does not result in 
boolean, it is: #{condition.type}:file:#@file, line:#$.!",caller
              end
              @stateArray << condition
              puts "#{line} : #{@stateArray.to_s}" if $DEBUG
              puts "condition is: "+condition if $DEBUG
           when /^#>ELSE/
              #invert condition
              @stateArray[-1] = !@stateArray[-1]
              puts "#{line} : #{@stateArray.to_s}" if $DEBUG
           when /^#>END/
              @stateArray.pop
              puts "#{line} : #{@stateArray.to_s}" if $DEBUG
           when /^#>INCLUDE/
              fields = line.split
              file = fields[1].strip
              puts "file to include is: #{file}" if $DEBUG
              fileString << include(fields[1].strip) if allTrue?
           else fileString << line if allTrue? 
        end
      }
      fileString.interpolate(b) 
   end

   private 
   def include(file)
      tf = TemplateFile.new(file,@bind)
      tf.interpolate
   end
   def allTrue?
      bool = true
      @stateArray.each {|entry|
         bool = bool && entry
      }
      return bool
   end

end

#test it:
if $0 == __FILE__
   var = "string"
   i = 0
   tf = TemplateFile.new("tests/vhdl",binding)
   5.times do |i|
      puts "for i==#{i}:"
      puts tf.interpolate(binding)
   end
end
#End of template.rb

Here's the file I used for testing, call it "vhdl" and put it in a subdir 
called 'tests', then you can run: ruby template.rb:
--vhdl
#>INCLUDE license.txt
entity vector_#{i} is
   port(
      data_in:in STD_LOGIC_VECTOR(#{i} downto 0);
      data_out:out STD_LOGIC_VECTOR(#{i} downto 0);
   );
end

architecture arch_vector_#{i} of vector_#{i} is
begin
signal vector(0 to #{i}) = "#{"X"*(i+1)}";
#>IF #{i<2}
--this comment means that i is less than 2
   #>IF #{true}
--you shouldn't be printing this if i is >= 2
      #>IF #{i>0}
--You'll see this if i is greater than 0 and i < 2
      #>ELSE
--You'll see this only if i == 0
      #>END
   #>END
#>ELSE
--this comment means that i is greater than or equal to  2
   #>IF #{i==2}
--this comment means that i is equal to 2
   #>END
   #>IF #{i}
   #>END
#>END
end
--end of vhdl file

Oh, and here's the file included, license.txt:
#license.txtB
--------------------------------------
--this file is covered by the GPL
--creation time: #{Time.now.to_s}
--created by: #{$0}
--author: pt
--------------------------------------


Phil