Any For can be rewritten as a While right?

For[start,test,increment,body]

is the same as:

start;
While[test,body;increment;]

right?

I'm always hoping for some advanced coding caption in Mathematica: that the frontend recognises For loops and suggests Do loops or Table, and change Sort[...,f[#1] ==f[#2]] to SortBy[...,f] and Sort@*DeleteDuplicates to Union and so on.....

They were intended as pro For, because it is unusual sequencing... Though I would still write them as While loops I think, but very equivalent...

I think what Szabolcs means is that For is in 99% of the cases used for looping over a variable from a to b (or b to a). Though this can be perfectly done like (something like):

For[i=0,i<10,i++,
    body
]

there are several things that go often wrong:

1. == instead of =
2. <10 or <=10 (does that include 10 or not?) so you might 'miss' one, very common mistake
3. I used an 'i' in the example but imagine it is the variable that is a bit longer: loopvar1, then you have to type it 3x, if one of them is wrong, the program will likely break.
4. 'i' has to be unique and care must be taken it is not used elsewhere in the code, and I will keep a value afterwards.

This can all be solved using Do (or Table if you want to store each loop)

1. no need to type = or ==
2. it is immediately obvious what the begin and end is
3. variable is only typed once
4. variable is local and will be deleted after evaluation, it doesn't stay in memory like 'i' does in the For loop

Overall, the chance of making a mistake is just much smaller. Unless you have a loop that iterates in an unusual way e.g.:

For[i = 1, i < 200, i += i, Print[i]]

or

j = 0;
For[i = 1, i < 200, i += j; j++, Print[i]]

use Do. Like I said, nearly all for loops are used for 'linear sequences', and it is less error-prone than the equivalent Do/Table. Not to mention the execution speed and parallelisation possibilities if one uses Table.

@Sander, @ Szabolcs. Thank you for the comments! At least, your opinions are clear. For[] is a sensitive construct prone to generate errors hard to detect. It has also the problem of readability. Conclusion: it is recommended for Mma novices to avoid its application.

I think your question is related to how Mma uses pattern matching in its function invocation syntax.

There is a lot of subtlety to understand and use defensively, in code, in order to make sure the semantics can be derived from the syntax.

I do not think the parsing system can help much with this.

HTH.