Skip to main content

Choosing an Assignment Operator

If you were to write your own programming language (as I still intend to do someday even if only for the learning experience it provides me), what symbol (or symbols) would you use to represent the assignment operator?

Even though it would looks like BNF or old-school Pascal, I would lean towards using := as the assignment operator. That would leave me free to use = for equality and there wouldn't be the issue of = vs. == tripping up new programmers. Besides, performing assignments is more common than making comparisons, so perhaps assignment should have the more distinct operator. Going one step further, if the language I wrote was not strongly typed, I would use == as the identity operator (as like PHP's ===). := and = to == seems a more logical progression to me than = and == to ===.

I suspect I wouldn't use = as both assignment and comparison as Basic does because of the ambiguity it causes. For example:
x = y = 0
Does this mean "assign 0 to both x and y", or "assign the boolean comparison whether the value of y is 0 to x?" Statements such as these:
x := y = 0
x := y := 0
are then both clear in their meaning.

I think my second choice would be just : and have something like:
x: 2 + 2
The lvalue appears as if it were a label, giving the visual representation that x means 2 + 2. Plus, it would be one (of many) syntaxtic differences that would separate my language from the others. I don't know of any languages that currently use : as an assignment operator.

Of course, this all presumes the elements of a statement are written in a certain order. If you were to use a keyword such as set:
x set 2 + 2
just appears awkward to me. It would have to be:
set x 2 + 2
But if you always require the assignment target on the left-hand side of your operator, then is an explicit assignment operator really required as all? The implied assignment operation of something like:
x 2 + 2
is clean and succinct.
Labels:

Comments

  1. MTNovember 28, 2008 at 9:28 PM

    This makes visual sense to me.

    x <- 2 + 2

    ReplyDelete
  2. AnonymousMay 21, 2011 at 7:09 AM

    I’d like to use “←” for assignment! ;-)
    x ← 2 + 2
    NB my favorite OS doesn't star with “Windows…” but ends with “…Linux” |-D

    ReplyDelete

Post a Comment

Popular posts from this blog

Writing a Minimal PSR-0 Autoloader

An excellent overview of autoloading in PHP and the PSR-0 standard was written by Hari K T over at PHPMaster.com , and it's definitely worth the read. But maybe you don't like some of the bloated, heavier autoloader offerings provided by various PHP frameworks, or maybe you just like to roll your own solutions. Is it possible to roll your own minimal loader and still be compliant? First, let's look at what PSR-0 mandates, taken directly from the standards document on GitHub : A fully-qualified namespace and class must have the following structure \<Vendor Name>\(<Namespace>\)*<Class Name> Each namespace must have a top-level namespace ("Vendor Name"). Each namespace can have as many sub-namespaces as it wishes. Each namespace separator is converted to a DIRECTORY_SEPARATOR when loading from the file system. Each "_" character in the CLASS NAME is converted to a DIRECTORY_SEPARATOR . The "_" character has no special ...
6 comments
Read more

Safely Identify Dependencies for Chrooting

The most difficult part of setting up a chroot environment is identifying dependencies for the programs you want to copy to the jail. For example, to make cp available, not only do you need to copy its binary from /bin and any shared libraries it depends on, but the dependencies can have their own dependencies too that need to be copied. The internet suggests using ldd to list a binary’s dependencies, but that has its own problems. The man page for ldd warns not to use the script for untrusted programs because it works by setting a special environment variable and then executes the program. What’s a security-conscious systems administrator to do? The ldd man page recommends objdump as a safe alternative. objdump outputs information about an object file, including what shared libraries it links against. It doesn’t identify the dependencies’ dependencies, but it’s still a good start because it doesn’t try to execute the target file. We can overcome the dependencies of depende...
Post a Comment
Read more

A Unicode fgetc() in PHP

In preparation for a presentation I’m giving at this month’s Syracuse PHP Users Group meeting, I found the need to read in Unicode characters in PHP one at a time. Unicode is still second-class in PHP; PHP6 failed and we have to fallback to extensions like the mbstring extension and/or libraries like Portable UTF-8 . And even with those, I didn’t see a unicode-capable fgetc() so I wrote my own. Years ago, I wrote a post describing how to read Unicode characters in C , so the logic was already familiar. As a refresher, UTF-8 is a multi-byte encoding scheme capable of representing over 2 million characters using 4 bytes or less. The first 128 characters are encoded the same as 7-bit ASCII with 0 as the most-significant bit. The other characters are encoded using multiple bytes, each byte with 1 as the most-significant bit. The bit pattern in the first byte of a multi-byte sequence tells us how many bytes are needed to represent the character. Here’s what the function looks like: f...
1 comment
Read more