On Mar 24, 2005, at 1:28 PM, Mark Wieder wrote:
Actually I'd like variable typing as well <g>. But only when I want it. Otherwise I also like the freedom and the fact that the engine converts everything for me. No more ugly casts. Not declaring variables before use, though... consider
on Gimme val1, val2
put val1 * 10 into val3 put val2 * 5 into val5 return val3 + val4 end Gimme
where I accidentally typed "val5" instead of "val4" (slip of the finger). You're not going to find this error (if you find it at all) until runtime. The simple addition of the line
local val3, val4
and enabling variable checking allows you to catch the error at the time you click the "Apply" button. Why not let the compiler help you?
However, that is stronger than what you need to catch this particular problem.
The declaration adds redundancy, just as a checksum at the end of a message might add some redundancy for checking. In general, there is nothing wrong with that. (As always, the trick is to have a rich and productive language with just the right amount of redundancy.)
Here are some ways that would not need the redundancy:
1
In this particular narrow case, constant folding would catch this. Suppose "val3 + val4" is translated to this:
plus( makeNumber( fetch( getVar("val3") ), makeNumber( literal("val4") ) )
By the time constant simplification gets to the second makeNumber(), it will create an error.
2
This can also be caught by a compiler warning of unused variables or data flows. Container val5 is unused.
3
If, just as an example, the language was changed to not allow unquoted literals or the use of uninitialized variables, then the use of val4 would create an error.
4
This can also be caught by other heads-up methods. If the editor was super smart, it could italicize names known to represent numbers. The person typing this might catch that val4 is the only container not italicized.
5
Hmmm. An analysis like that would catch things even the constant simplification would not catch. It would allow the compiler to remove the makeNumber() in some cases. OK. I'll add this kind of compiler checking to my list.
Even though the declaration is stronger than what is needed to catch this, it is not as strong as typing as some might think of typing.
Just musing. I ain't picking on any of this.
Should the redundant decoration on 'end' be optional?
Dar
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