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Coding Convention
=================
Introduction
------------
This document stipulates the coding convention for NERV. The convention applies
to both Lua and C.
Naming
------
- Variable and function names should only contain lower case alphabets, digits or hyphens.
- In a local scope, simple names can be used to ease typing:
.. code-block:: lua
function a_meaningful_function_name(something)
-- "sth" is used to aid typing
local sth = something.thing
sth.description = "just a trival thing"
sth.action = function () end
end
- For global names, meaningful phrases should be used to describe the functionality.
.. code-block:: lua
input_size = 429
output_size = 3001
hidden_size = 2048
- Use phrasal verbs to describe operations.
.. code-block:: lua
function Container:initialize()
-- some initialization
end
function Container:append()
end
function Container:get_next()
end
function set_handler()
end
- Class names (in Lua) are in "`UpperCamelCase`_".
.. code-block:: lua
local mat_cls = nerv.CuMatrixFloat
-- keep abberivations in upper case
local reader_cls = nerv.HTKReader
.. _`UpperCamelCase`: https://en.wikipedia.org/wiki/CamelCase
Indentation
-----------
- Four *spaces* are used for one identation level. DO NOT use tabs.
- Lines should be indented with a nested block:
.. code-block:: lua
function this_is_a_function(a, b)
local sum = 0
-- four-space indentation is required here
for i = a, b do
-- another nested block
sum = sum + i
end
return sum
end
Line Breaking
-------------
- Each line contains 80 characters at most (100 characters when a line is hard
to break).
- DO NOT try to put everything in a single, long line. It would only make your
code look stupid and obscure rather than provide with any simplity or
elegance.
- Break long function invocations like this: (make sure the left side of
multi-line arguments are aligned and at least one level of indentation is
required for each nested invocation)
.. code-block:: lua
a_very_very_long_object_name:a_very_very_long_method_name(long_argument1,
long_argument2,
long_argument3)
a_very_very_long_object_name
:an_even_longer_version_of_method_name(long_argument1,
long_argument2,
long_argument3)
a_very_very_long_object_name:a_very_very_long_method_name(
long_argument1,
there_is_a_nested_invocation_of_another_function(argument1, argument2)
long_argument3,
long_argument4)
- Multi-line Lua tables should be like this:
.. code-block:: lua
local very_very_very_very_long_table_name = {
-- avoid writing the verbose form: ["key"] = value,
-- as long as the key is a string
key1 = value1,
key2 = value2,
key3 = value3,
key4 = { -- another table
k1 = v1,
k2 = {
even = 1,
deeper = 2,
tabl = {
-- can go deeper
}
},
k3 = {
a = 2,
b = 3,
c = 4
},
-- short table can be in-line
k4 = {a = 1, b = 2, c = 3},
[2333] = "number as a key",
[{this = 1,
is = 2,
rare = 3}] = "table as a key"
},
-- another style of table: write the first key-value
-- pair in the same line as "{" and the last pair in
-- the same line as "}"
key5 = {a = 1,
b = 2,
c = 3}
}
Statements
----------
- Lua is NOT C, so DO NOT put an extra pair of parentheses in ``if`` statements:
.. code-block:: lua
local C = 0
local lua = 1
-- good style
if lua ~= C then
print("Lua is not C.")
end
-- bad style
if (lua == C) then
print("You seriously?")
end
- Try to use Lua-style ``for`` to iterate through all elements:
.. code-block:: lua
function get_list(n) -- use closure to make an iterator
local i = 0
return function ()
i = i + 1
if i == n then
return nil
else
return i
end
end
end
local list = { -- emulate an object
i = 0,
n = 10,
get_next = function(self)
self.i = self.i + 1
if self.i == self.n then
return nil
else
return self.i
end
end
}
-- good style (for iterators)
for e in get_list(10) do
print(e)
end
-- good style (for objects)
for e in list.get_next, list do
print(e)
end
-- bad style
local iterate = get_list(10)
while true do
local e = iterate()
if e == nil then break end
print(e)
end
Remarks
-------
It is difficult to enumerate all possible code constructs to precisely describe
the convention. Therefore, when in a doubt, please refer to core NERV and try
to be consistent with existing code. Also, there is still some code in NERV
that is not compliant to some of the convention stipulated above, if so, please
contact the developers.
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