templates.md

Headers and Decorators

Template

Templates using decorators

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:

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

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

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

When a function is decorated with the template decorator:

• The templates are only available to the decorated function.
• If the function is decorated with two templates with the same name, the first one gets overridden.

The arguments of the decorator are:

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

---

Note: The arguments name and types could also be passed of the form @template('T', ['int', 'float']) without specifying the keywords.

---

Examples

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

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

In this example the arguments of g can either be a 1d integer array or a 2d integer array.

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

The following shows a slightly more complex example:

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

In this example h will have one of the following 2 prototypes:

def h(a : 'int', b : 'int[:]'):
  pass
def h(a : 'float', b : 'float[:]'):
  pass