The Shape of Code

WG9, the Ada Standard committee, are looking into adding support for operator assignment in the next revision of the language standard. Ada was designed back in the day when C’s operator assignments, such as +=, were a novelty (all the languages we know today that follow C’s lead, including choice of operator precedence, did not yet exist); developers using serious languages knew that typing everything out in full was good for you.

It’s amazing to read about “… those who have been damaged by terser languages…”, in the proposal comments. Do I only think that My_Package.My_Array(I).Field +:= 1; is so much easier to read than My_Package.My_Array(I).Field := My_Package.My_Array(I).Field + 1; because my brain has been damaged? In the second statement I have to parse two subexpressions and notice that they refer to the same object, while the first statement only requires me to parse one subexpression and the +:= operator tell me that something is being added to its value. The first statement requires a lot less effort and is likely to be less error prone (I bet Ada programs make cut and paste error just like the rest of us).

Did you notice the use of round brackets to specify an array index? Yes, the eighties were the decade when the programming language world was badgered into being politically correct and only require the use of characters that appeared on every European country’s keyboard.

The Ada proposal started out following the C convention, e.g., +=, *=, etc, then switched to :+, :*, etc. The assignment token in Ada is := and there is a logic to switching out the = for another operator. However, I would argue that +:, *:, etc would be a less error prone ordering or characters. People pay more attention to the first character in a sequence and somebody in a hurry may not notice that the colon is not followed by a =; putting the ‘unexpected’ character first is more likely to catch reader attention.

Another proposal is for the @ token to act as a placeholder. The only place I can see this being useful on any regular basis is in bitwise manipulation: My_Package.My_Array(I).Field := (@ << 16) or @ ; (Ada does not support << as an operator, so reality is a bit more complicated than this). I don't think there are enough situations where placeholders would be useful to warrant using a solution that is more complicated than operator assignment.

One proposed advantage of the new fangled operators is making life easier for non-Ada users (see the discussion in the proposal comments). The I have put lots of efforts into Ada, why should others have it easy die-hards are fighting a rear guard action to make sure life is not too easy for newcomers.