Rafal Skolasinski authored 6 years ago and Joseph Weston committed 6 years ago

Previously we were manually computing the position from
the site tag an an extra 'grid_spacing' parameter. Even
though we now have one additional Python function call,
using the position as determined by the underlying lattice
is less susceptible to bugs.

Closes #199.

Rafal Skolasinski authored 7 years ago and Joseph Weston committed 7 years ago

A regression in Sympy causes symbols that are invalid
identifiers to be created, e.g. '-B_x'. While we cannot
fix Sympy's behaviour, we can at least shield our users
from its quirks.

Closes #179.

Previously, the wording of the explanatory comment above
discretized hopping functions was confusing. Now we
are clear about where the hopping originates.

Fixes #173.

Some API functions call other API functions that report warnings.
We need to increase the stacklevel so that the user sees their
own line of code in the warning message.

The warning used to be emitted from build_discretized().  Whenever
discretize(), another API function that internally calls
build_discreitzed() would be called with the deprecated argument, a
warning would appear for a line in the code of discretize().

This has been fixed by factoring out the check, and calling it from both
functions.

"grid" parameter takes role of "grid_spacing" and extends its
functionality. It can take scalar values, as "grid_spacing",
as well as "kwant.lattice.Monatomic" object. Currently there
are strong contraints of accepted lattice but they can be lowered
later when new functionality will be provided. "grid_spacing" is
being deprecated.

Calling "expand" at this point is not required and differs from
sympy behaviour without a good argument for it. Closes #146.

"monomials" are not yet a public function. Interface improvment consists of:

- change "*gens" into single argument "gens" with default value "None".
- If left as "None" it reads all symbols present in the given "expression".
- It is also possible to provide "gens" as sequence of strings (symbol names).

If "expr" is already a SymPy object and "locals" are provided the
RuntimeWarning will be triggered.

closes #125

The purpose of keyword-only args is to allow functions that take a
variable number of args but also a variable number of "options" without
having to resort to (*args, **kwargs).  Builder value functions do not
fall into this category.  Hence, there is no reason to pay the price (in
terms of flexibility and efficiency) for not much gain.

e → expr
discrete_coordinates → discrete_coords
substitutions → subs

Rafal Skolasinski authored 7 years ago and Bas Nijholt committed 7 years ago

Calling "kwant.continuum.discretize('A * k_x', substitutions={'A': 'A + B'})"
ends with performing substitutions twice. Fixed by removing redundant second
substitution. Fixes issue #121.

Rafal Skolasinski authored 8 years ago and Joseph Weston committed 8 years ago

Arguments of "discretize", "discretize_symbolic", and "build_discretized"
that does not represent Hamiltonian or discrete coordinates are now keyword-only.
Also "lattice_constant" argument is renamed to "grid_spacing" in order to
distinguish it from real lattice constant of a crystal. Closes 110.

Rafal Skolasinski authored 8 years ago and Joseph Weston committed 8 years ago

Currently when 'build_discretized' receives onsite and hoppings to build
kwant template system it checks if the input expression contains
position operators as symbols. Because at this moment commutative relations
don't play any significant role it is enough to check by symbol names.

So far substitutions were accepted in form ''string key: sympy expression'',
which was extended to accept form of ''string key: string expression'.
Also 'substitutions' were only used when input 'hamiltonian' was not a sympy
object already, which got alternated to apply them always. Closes #97.