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Headers and Decorators

Template

Templates using header comments

A template in pyccel, is used to allow the same function to take arguments of different types from a selection of types the user specifies.

The usage

In this example the argument a, could either be an integer or float, and the same for the argument b:

#$ header template T(int|real)
#$ header template Z(int|real)
#$ header function f(T, Z)
def f(a,b):
	pass

In this example The arguments a and b, should both be integers or floats at the same time:

#$ header template T(int|real)
#$ header function f(T, T)
def f(a,b):
	pass

When a function is declared using a header comment as above:

  • The function can access the templates declared in its parent's scopes.
  • A template declared in the same scope as the function overrides any template with the same name in the parent's scopes.

Examples

In this example the template T can be used to define the arguments types of the nested function f2:

#$ header template T(int|real)
def f1():
	#$ header f2(T, T)
	def f2(a, b):
		pass
	pass

In this example the arguments of f2 can either be bool or complex, they can not be int or float:

#$ header template T(int|real)
def f1():
	#$ header template T(bool|complex)
	#$ header f2(T, T)
	def f2(a, b):
		pass
	pass

Templates using decorators

The usage

from pyccel.decorators import types, template
@types('T', 'T')
@template(name='T', types=['int','real'])
def f(a,b):
	pass

Arguments:

  • name: the name of the template
  • types: the types the tamplate represents.

Note: The arguments name and types could also be passed of the form @template(T, types=['int', 'real']) without specifying the keywords.and the order in which the decorators are called is not important.

When a function is decorated with the template decorator:

  • The templates are only available to the decorated function.
  • The templates overrides any existing templates with the same name (declared as header comment).
  • If the function is decorated with two templates with the same name, the first one gets overrided.
Examples

In this example the arguments of f can either be bool or complex, they can not be int or float.

from pyccel.decorators import types, template
#$ header template T(int|real)
@types('T', 'T')
@template(name='T', types=['bool','complex'])
def f(a,b):
  pass