Coding Style

Coding style for Ciao code

• Keep line width less than 80 characters (if possible).
• Do not leave lines ending with spaces or tabs (trailing whitespace).
• Any file should be ended by a new line.
• Use spaces instead of tabulations.
• Avoid predicates with the same name but different arity.
• Use descriptive module names, specially in libraries (to avoid clash with user-defined modules, since module names are global).
• Similarly use descriptive names for multifile predicates (they are global).
• When possible enumerate imported predicates explicitly.
• When contributing bug reports, they are typically stored at <bundle>/bugs/Pending. When fixed, bug entries are moved to <bundle>/bugs/Fixed. Place at <bundle>/bugs/Unclassified potential bugs whose status may be unknown.
• Make sure that you make proper usage of clause indexing (in Ciao it is done by default on the first argument of predicates) and cuts (!/0), for the expected instantiation modes for each predicate. Doing unnecessary backtracking and leaving choice points can introduce nasty performance bugs that can be hard to debug. Assertions can help in this task.
• Understand the algorithmic cost of operations (e.g., assert/consult is typically linear in the size of terms, var-nonvar unification is typically constant time, etc.)

Coding style for C Code

• In general, avoid inline functions (see Linux Kernel Coding Style) -- unless you can collect evidence that they produce optimal code (size and speed) with the state of the art C compilers.
• Use macros (even big ones) when you need to inline code. A macro is much better than duplicated code.
• Do not use comma at the statement level (e.g. int a, b; or foo(), bar();) since that confuses the CPP macro expansion (when that code is wrapped inside {} and passed as argument).
• goto is not harmful for low level code (specially for automatically generated code).

Some helper Emacs tools

To highlight trailing whitespaces you can either:

• use the highlight-chars emacs package (available at MELPA) and add the following lines in your .emacs:

;; ---------------------------------------------------------------------------
;; highlight tabs and trailing whitespace
(require 'highlight-chars)
(add-hook 'font-lock-mode-hook 'hc-highlight-tabs)
(add-hook 'font-lock-mode-hook 'hc-highlight-trailing-whitespace)

• toggle the Show Trailing Whitespace option on, which can be found at Options > Customize Emacs > Browse Customization Groups below:

[-]-\ Group Emacs
   [-]-\ Group Editing
    | [-]-\ Group Editing Basics
    |     `--- Option Show Trailing Whitespace

It is not adviced to remove trailing whitespace automatically since this can mess up the diff of your changes (and potentially lead to merge conflicts later on).