An empirical study to determine if identifier-naming conventions (i.e., camelCase and under_score) affect code comprehension is presented. An eye tracker is used to capture quantitative data from human subjects during an experiment. The intent of this study is to replicate a previous study published at ICPC 2009 (Binkley et al.) that used a timed response test method to acquire data. The use of eye-tracking equipment gives additional insight and overcomes some limitations of traditional data gathering techniques. Similarities and differences between the two studies are discussed. One main difference is that subjects were trained mainly in the underscore style and were all programmers. While results indicate no difference in accuracy between the two styles, subjects recognize identifiers in the underscore style more quickly.
The home page for the Rust language is a great piece of design: it explains what’s going on and points you to all the most interesting resources, without wasting any time. The “short summary of features” and “taste of what it looks like” answer the first questions anyone might have when investigating the language. I should build something similar for Radian.
Following from yesterday’s design discussion, here is the plan I am considering for platform-specific code.
At present, a statement of the form
import foo generates an extern reference to an object named
foo, then pushes “foo.radian” onto the compile queue. When the compiler reaches “foo.radian”, it generates a static singleton object named
foo whose members are the declarations found the file.
The new system will add awareness of the target OS and architecture. Instead of searching for “foo.radian”, the compiler will search through a sequence of possible file names. Where $OS is the OS component of the LLVM target and $ARCH is the architecture component, the compiler will search for these files, in order, compiling the first one it finds and ignoring the rest:
We already have a distinction between the module name,
foo, and the file name, “foo.radian”; this change will simply add an additional, optional suffix to the file name, leaving the module name unchanged. Since the compiler will always search for each possible implementation file in order, it will be impossible to import more than one different implementation of the same module for a single target build.
I chose the hyphen instead of Go’s underscore because it is already forbidden from module names. This means it is impossible to accidentally import against a specific platform implementation; even if you only supply an implementation of the file for a single platform, you must always import the module name alone.
Currently supported values of $OS would be “linux” and “macosx”, while $ARCH can be “i386″ or “x86_64″.
The Go language uses OS- and architecture-specific file name suffixes to identify platform-specific implementations of a module. There is a more complex system of build constraints of which the name suffix is only one example, but it’s a pretty powerful convention.
I wonder if a similar scheme would work for Radian. Import statements are already abstracted from filenames, after all – one imports a library named “foo.radian” with the statement
import foo and not a more C-style
import "foo.radian". Perhaps the build tool could first check for a file named “foo_macos.radian”, if one happens to be targeting Mac OS, and only fall back to “foo.radian” if no platform-specific file exists.
In C++ code, one typical pattern is to define an abstract base class whose methods implement common behavior, calling pure virtual functions for platform-specific operations. Each platform then defines a subclass which implements those methods. Another similar strategy uses the bridge pattern: instead of subclassing, the general class delegates its operations to a platform-specific implementation object.
How might we use this strategy in Radian, if its import statement could transparently pick an appropriate implementation file for the target platform?
In order to use the abstract-base-class approach, we’d have to introduce the notion of module inheritance. Your
import foo would actually target
foo_linux.radian, or whatever was appropriate, and each implementation would then somehow declare itself to be an extension of
foo_common.radian. Perhaps this would all happen magically if the build tool observed the presence of both a
foo_platform.radian file and a
foo.radian file, but it seems like a lot of magic – and if we’re going to postulate the introduction of a module-inheritance scheme, it seems likely that people might want to use it for purposes other than simply isolating platform-dependent code; it should be called out explicitly.
This makes me think the bridge pattern is a better bet. If you were to design a network library, for example, you might define a
network.radian which provides the public API. This file might then be packaged with
network_internal_linux.radian. The main
network.radian module would then
import network_internal, automatically picking up the appropriate version for the current target. External users would
import network.radian and use some reasonable library API, while the library itself would delegate its grungy details to the methods in the platform-specific files.
Given that Radian requires source file names to consist of a legal identifier followed by the extension “.radian”, it might make more sense to use a hyphen or a period than an underscore. Imagine
network_internal-linux.radian, for example, which you’d
import network_internal and then refer to via
x = network_internal.foo(y) and the like.
Every programming language which manipulates strings offers a pair of functions which convert text to upper or lower case. These functions are often used to perform case-insensitive comparisons – you just convert both strings to either upper or lower case first. This generally works, but it fails for some scripts, and so the Unicode standard defines a case-folding transform which produces a normalized string suitable for caseless matching.
Radian’s string library implements
to_lower, and it seems reasonable that it should offer a case-folding function too. But what to call it? Nobody else seems to be offering such a function: I can’t find one in .NET, in Python, in PHP, in Ruby – Go has a mysterious function called SimpleFold, but whatever it’s doing, it isn’t what I’m trying to do.
- Fixed a bug in the garbage collector copy-forwarding mechanism which caused strange runtime library assertion failures after
- No longer misassigns a terminator byte when performing concatenations of certain very short strings.
conststatement renamed to
def. The semantics are the same; only the keyword has changed. The statement never created a constant in the mathematical sense; it simply defines a name for a value which cannot be redefined.
- Importing a file whose name begins with an underscore no longer fails, trying to load a mangled version of the file name instead. While the compiler does not enforce this convention, prepending a file name with an underscore is a way to show that the file contains private implementation details and should not be imported from outside the directory which contains it.
- No longer misprocesses hex character escapes inside string literals.
- More specific error message when you try to modify the
selfobject inside a function and not a method.
- More helpful error message when an
importstatement fails: now points at the location of the import statement which failed. This might happen if you typo the import name and accidentally specify a file which does not exist.
- Fixed a race condition in the parallel work dispatcher which sometimes caused a null dereference crash.
I have added two new entries under Documentation: a writeup about the map object and another about the string object. These pages describe the syntax, list the methods and functions offered by the objects, and discuss the computational complexity of the available operations.
Interesting research from Microsoft on equipping compilers with information necessary to automatically parallelize code via reference immutability tagging:
A key challenge for concurrent programming is that side- effects (memory operations) in one thread can affect the be- havior of another thread. In this paper, we present a type sys- tem to restrict the updates to memory to prevent these unin- tended side-effects. We provide a novel combination of im- mutable and unique (isolated) types that ensures safe paral- lelism (race freedom and deterministic execution). The type system includes support for polymorphism over type quali- fiers, and can easily create cycles of immutable objects. Key to the system’s flexibility is the ability to recover immutable or externally unique references after violating uniqueness without any explicit alias tracking.
A slideshow by Rob Pike, one of the principal inventors of Go. I was surprised by the number of places I found myself nodding along in agreement, having independently arrived at similar opinions about the Way Things Ought To Be Done.
Go has definitely taken over a big piece of the ground I had originally intended to cover with Radian, but I still think there’s room for a comparable language on the more dynamic / scripty end of the scale. Go is a tool for concurrent programming in the large, but there are lots of people who work in the terrain originally occupied by shell scripts and currently dominated by Python, Ruby, and to a decreasing degree Perl, and I think Radian has something to offer there.
$low = lc $str; $hi = uc $str;
low, hi = (str.lower(), str.upper())
low, hi = str.downcase, str.upcase
String low = str.toLowerCase(); String hi = str.toUpperCase();
var low, hi = strings.ToLower(str), strings.ToUpper(str)
string low = str.ToLower(); string hi = str.ToUpper();