In general we aim to follow the Julia Style Guide but there are some exceptions due to our specific needs and a different background.
The content of this page are merely guidelines. There may be good reasons to deviate from them in some cases; in that case just do so.
The usual Julia naming conventions apply to OSCAR, too (that said, for various reasons our code still violates quite some of them; but in general we strive to reduce these). Here is a summary of the naming convention followed in OSCAR:
CamelCasefor types and
snake_casefor everything else. (Internal functions do not have to follow these rules.) Types (and their constructor) tend to be in
CamelCase. However, please also provide the constructor (or a constructor) in
snake_case. As a user one usually does not know if something is a constructor or a function.
- Noteworthy difference to Julia base is that we do not have exceptions for
has*as prefix. It is
hasbar. The main reason is to avoid awkward constructions like
isvery_ample, while also being consistent. For compatibility with standard Julia, while staying consistent internally, we also provide aliases (using
AbstractAlgebra.@alias) for various standard Julia functions, e.g.
is_oneas alias for
- For generic concepts choose generic names, based on general algebraic concepts, preferably not special names from your area of speciality.
- Use Julia conventions where applicable and when they don't contradict our own rules above.
- In Julia we have multiple dispatch, so we do not need functions like
point_from_matrixas the "from" part is clear by the type of the argument. It should be called
points(T::Matrix)in some variation. Similarly for
matrix_to_points. Of course it is fine to use them internally, where useful.
- Follow the mathematics. If your function needs a list of points, you should create a point-type (or use the one already there) and then use this. For user-facing functions, please do not use re-purposed lists, arrays, matrices...
- If already existing types in OSCAR are almost what you need, consider improving them instead of writing your own. While it might be tempting to create a new polynomial ring type for the new application because some feature is missing, it causes a lot of work and compatibility issues: Will the new type support
- normal functions (gcd, factor),
- quotient fields,
- modules and residue rings,
- conversion to and from other already existing types?
- Whenever functions return the same mathematical object, but in different mathematical categories, the first argument should be the desired return type. One example is
projective_space(ProjectiveScheme, *). However, if the return type is different, even if the result describes the same mathematical object, it should be indicated in the function name, for example
As most modern programming languages, Julia allows the use of Unicode, e.g.,
α, in the REPL as well as in source code. As this reduces accessibility to various groups of users and developers, the use of Unicode should be kept to a minimum. Here is a general principle:
Do not use Unicode characters inside functions. See below for the exception concerning printing.
Per default output should be ANSI only (no Unicode). Implementors of
Base.show and related functions can branch on the output of
Oscar.is_unicode_allowed() to display objects using non-ASCII characters. This will then be used for users which enabled Unicode using
allow_unicode(true). Note that
- there must be a default ANSI only output, since this is the default setting for new users, and
- OSCAR library code is not allowed to call
Here is an example with and without output using Unicode:
struct AtoB end function Base.show(io::IO, ::AtoB) if Oscar.is_unicode_allowed() print(io, "A→B") else print(io, "A->B") end end
- Do not use tabs.
- Do not put spaces "inside" parenthesis.
- Do put spaces after commas.
f(x, y) = x + 1 print(f(1, 2))
f( x,y ) = x + 1 print( f ( 1,2 ) )
forloops should use
- don't put spaces around the
:in a range
for i in 1:3 println(i) end
for i = 1 : 3 println(i) end
do not nest loops and
ifclauses too deeply; if you are using 5 or more levels, then in general that's a hint that you should refactor; e.g.
- by moving parts of the code into a separate function
- by replacing guard constructs like
for i in A if flag ... end end
for i in A if !flag continue end ... end
for i in A flag ||continue ... end
- by merging loops: you can replace
for i in A for j in B ... end end
for i in A, j in B ... end
Functions should not have too many arguments. If you need a bunch arguments, chances are that introducing a new type makes it more readable.
Functions should not be too long; very long functions are in general harder to understand; it is also more difficult to see all the code at once. Consider splitting the function into multiple ones, if it is sensibly possible.
However, as always, rules sometimes should be broken.
Sometimes it is necessary to rename a function or otherwise change it. To allow for backwards compatibility, please then introduce a new line in the file
src/Deprecations.jl. The syntax is as follows:
# Deprecated after CURRENT_RELEASE_VERSION @deprecate old_function(args) new_function(args)
It is possible to transform the
args too, if the syntax has changed. If this process needs an auxiliary function, which otherwise is unnecessary, please add it above:
# Deprecated after CURRENT_RELEASE_VERSION function transform_args_for_new_function(args) # Do something return new_args end @deprecate old_function(args) new_function(transform_args_for_new_function(args))
The comment about the version number is only necessary if you are the first one adding to
Deprecations.jl after a release, otherwise please add to the existing block.
Please make sure to change to the new function everywhere in the existing OSCAR code base. Even if you think, you were the only one using the function, run a quick
grep to make sure. When you are done,
Deprecations.jl should be the only place mentioning
old_function. To make sure, you can start Julia with
--depwarn=yes or even
--depwarn=error and then run the tests.
In general we try to follow the list of recommendations in the Documentation section of the Julia manual.
Via the MathJax integration it is possible to use LaTeX code, and this is the preferred way to denote the mathematical symbols in the docstrings.