.. _stdlib_templates:

===============================================
decltype macro and template function annotation
===============================================

.. das:module:: templates

The TEMPLATES module implements template instantiation utilities for daslang
code generation. It supports stamping out parameterized code patterns with
type and value substitution.

See also :doc:`templates_boost` for template substitution and code generation.

All functions and symbols are in "templates" module, use require to get access to it.

.. code-block:: das

    require daslib/templates



++++++++++++++++++++
Function annotations
++++++++++++++++++++

.. _handle-templates-template:

.. das:attribute:: template

This macro is used to remove unused (template) arguments from the instantiation of the generic function.
When [template(x)] is specified, the argument x is removed from the function call, but the type of the instance remains.
The call where the function is instanciated is adjusted as well.
For example::

    [template (a), sideeffects]
    def boo ( x : int; a : auto(TT) )   // when boo(1,type<int>)
        return "{x}_{typeinfo typename(type<TT>)}"
    ...
    boo(1,type<int>) // will be replaced with boo(1). instace will print "1_int"




+++++++++++
Call macros
+++++++++++

.. _call-macro-templates-decltype_noref:

.. das:attribute:: decltype_noref

This macro returns TypeDecl for the corresponding expression, minus the ref (&) portion.


.. _call-macro-templates-decltype:

.. das:attribute:: decltype

This macro returns ast::TypeDecl for the corresponding expression. For example::

    let x = 1
    let y <- decltype(x) // [[TypeDecl() baseType==Type tInt, flags=TypeDeclFlags constant | TypeDeclFlags ref]]