digitalmars.D - Re: D const design rationale
- Regan Heath <regan netmail.co.nz> Jun 27 2007
Oskar Linde Wrote:Walter Bright skrev:Oskar Linde wrote:Walter Bright skrev:OF wrote:Walter Bright Wrote:BLS wrote:I am afraid you will not like this idea, but not afraid enough. <g> Why not using a single keyword "const_" adding a number 1, 2, 3 to represent : invariant, final, readonlyview. the higher the number the higher (the stronger) the const. means : const_3 == invariant; At least a mental help, IMO; somehow borrowed from Modula 2 processes.
I'm curious. Was 'readonly'
readonly is a synonym for const, so no improvement there.
Read-only isn't synonymous with constant.
Consider ROM, i.e. "Read Only Memory".
Yes, there are cases where the meaning of read-only and constant overlap. You could even argue that the overlapping meanings are large enough to make the words synonymous, but that is irrelevant to the discussion. What is relevant is which word does best describe the properties the D2.0 'const' has? IMHO, read-only wins by a large margin. Read-only describes everything 'const' is, while the generally accepted meaning of constant is a poor fit. This has been irking me for quite some time, and I believe it is the reason the final-const-invariant thing feels so awkward (to me). The design has been carefully considered and is quite likely the best possible given the requirements. However, the use of "const" to mean read-only sticks out like a turd in a punch bowl (pardon the expression). People argue that of the different meanings of "const" in C++ (that you like to point out), the non-constant meaning is the worst and most confusing. Still, the only meaning for "const" that D inherit from C++ is that one. <parenthesis> I've never heard anyone complain about "const" as a "storage class", like in: const double e = 2.7182818284590452354; const double pi = 3.14159265358979323846; <parenthesis> I believe *many* people would be *much* less confused and have a *much* easier time acceping and grasping the D const behavior if better keywords were used. "What? Const means it can change???" So I plead: Please reconsider the keywords. The implications of not doing that are severe. The publics acceptance of D is at stake. What if you could say, "Look: We fixed C++'s const. Const now really means constant -- not could-actually-change and you will be damned if you assume anything else". This is a hypothetical scenario of changing final-const-invariant -> final-readonly-const. There could possibly be even better choices of keywords. Apologies for being so harsh (and hyperbolic), but I feel this is (as strange as it may sound) a quite important issue.
I like this suggestion. votes++ Regan Heath
Jun 27 2007