Procedural Perl

This example illustrates a how Taco can be used to interact with procedural Perl modules — importing them, calling functions, and interacting with variables.

• Calling functions to perform calculations

  We begin by importing the Taco class and constructing an instance of it which launches a Perl sub-process. Now we can calculate the sine of 30 degrees by calling Perl’s sin subroutine (from the CORE:: namespace). This should give the expected value of a half.

  from taco import Taco
  
  taco = Taco(lang='perl')
  
  print('{0:.2f}'.format(
      taco.call_function('CORE::sin', radians(30))
  ))
  

  0.50
  

• Importing modules

  To make use of routines from other modules, they must be imported into the Perl interpreter running in the sub-process. The appropriate action to do this can be sent using the import_module() method. In the case of the Perl server, any arguments to this method are passed to the equivalent of a use statement. This allows us to bring the md5_hex subroutine into the current scope.

  taco.import_module('Digest::MD5', 'md5_hex')
  print(
      taco.call_function('md5_hex', 'Hello from Taco')
  )
  

  9442d82de2303664e42b60e103c0ead4
  

• A more convenient way to call functions

  Another way to call a function through Taco is by creating a convenience callable for it. The function() method, given the name of a function to be called, returns an object which can be called to invoke that function.

  md = taco.function('md5_hex')
  print(
      md('Useful for calling the same function multiple times')
  )
  

  47a533e6b83934f58c976de5f2b2dc5a
  

• Getting values

  We can retrieve the value of variables using get_value(). In this example, importing the “English” module gives a readable name for the variable containing the operating system name.

  taco.import_module('English')
  print(
      taco.get_value('$OSNAME')
  )
  

  linux
  

• Setting values

  set_value() can be used to assign a variable on the server side. In the case of Perl, setting the output field separator variable $, will configure the spacing between things which are printed out.

  taco.set_value('$,', '**')
  

  At this stage we can make use of some object-oriented code to check that the setting of $, has taken effect. For more information about using Taco with object-oriented Perl modules, see the object-oriented Perl example. Here we print the strings 'X', 'Y' and 'Z' to an IO::String object and check the result.

  taco.import_module('IO::String')
  s = taco.construct_object('IO::String')
  s.call_method('print', 'X', 'Y', 'Z')
  s.call_method('pos', 0)
  print(s.call_method('getline'))
  

  X**Y**Z