Tamil Names That Start With A
Rosetta Ockman
I couldn't come up with an answer except that some numbers can have text in them (123456L, 123456U) and that wouldn't be possible if the compilers were thinking everything with some amount of alpha characters was a variable name.
Compilers/parsers/lexical analyzers was a long, long time ago for me, but I think I remember there being difficulty in unambiguosly determining whether a numeric character in the compilation unit represented a literal or an identifier.
I agree it would be handy to allow identifiers to begin with a digit. One or two people have mentioned that you can get around this restriction by prepending an underscore to your identifier, but that's really ugly.
I think part of the problem comes from number literals such as 0xdeadbeef, which make it hard to come up with easy to remember rules for identifiers that can start with a digit. One way to do it might be to allow anything matching [A-Za-z_]+ that is NOT a keyword or number literal. The problem is that it would lead to weird things like 0xdeadpork being allowed, but not 0xdeadbeef. Ultimately, I think we should be fair to all meats :P.
When I was first learning C, I remember feeling the rules for variable names were arbitrary and restrictive. Worst of all, they were hard to remember, so I gave up trying to learn them. I just did what felt right, and it worked pretty well. Now that I've learned alot more, it doesn't seem so bad, and I finally got around to learning it right.
It's likely a decision that came for a few reasons, when you're parsing the token you only have to look at the first character to determine if it's an identifier or literal and then send it to the correct function for processing. So that's a performance optimization.
The other option would be to check if it's not a literal and leave the domain of identifiers to be the universe minus the literals. But to do this you would have to examine every character of every token to know how to classify it.
There is also the stylistic implications identifiers are supposed to be mnemonics so words are much easier to remember than numbers. When a lot of the original languages were being written setting the styles for the next few decades they weren't thinking about substituting "2" for "to".
Allowing use of variable names that began like a number would probably cause huge problems for the language designers. During source code parsing, whenever a compiler/interpreter encountered a token beginning with a digit where a variable name was expected, it would have to search through a huge, complicated set of rules to determine whether the token was really a variable, or an error. The added complexity added to the language parser may not justify this feature.
As far back as I can remember (about 40 years), I don't think that I have ever used a language that allowed use of a digit to begin variable names. I'm sure that this was done at least once. Maybe, someone here has actually seen this somewhere.
As several people have noticed, there is a lot of historical baggage about valid formats for variable names. And language designers are always influenced by what they know when they create new languages.
That said, pretty much all of the time a language doesn't allow variable names to begin with numbers is because those are the rules of the language design. Often it is because such a simple rule makes the parsing and lexing of the language vastly easier. Not all language designers know this is the real reason, though. Modern lexing tools help, because if you tried to define it as permissible, they will give you parsing conflicts.
OTOH, if your language has a uniquely identifiable character to herald variable names, it is possible to set it up for them to begin with a number. Similar rule variations can also be used to allow spaces in variable names. But the resulting language is likely to not to resemble any popular conventional language very much, if at all.
Because if you allowed keyword and identifier to begin with numberic characters, the lexer (part of the compiler) couldn't readily differentiate between the start of a numeric literal and a keyword without getting a whole lot more complicated (and slower).
C++ can't have it because the language designers made it a rule. If you were to create your own language, you could certainly allow it, but you would probably run into the same problems they did and decide not to allow it. Examples of variable names that would cause problems:
One of the key problems about relaxing syntactic conventions is that it introduces cognitive dissonance into the coding process. How you think about your code could be deeply influenced by the lack of clarity this would introduce.
Probably because it makes it easier for the human to tell whether it's a number or an identifier, and because of tradition. Having identifiers that could begin with a digit wouldn't complicate the lexical scans all that much.
Not all languages have forbidden identifiers beginning with a digit. In Forth, they could be numbers, and small integers were normally defined as Forth words (essentially identifiers), since it was faster to read "2" as a routine to push a 2 onto the stack than to recognize "2" as a number whose value was 2. (In processing input from the programmer or the disk block, the Forth system would split up the input according to spaces. It would try to look the token up in the dictionary to see if it was a defined word, and if not would attempt to translate it into a number, and if not would flag an error.)
Suppose you did allow symbol names to begin with numbers. Now suppose you want to name a variable 12345foobar. How would you differentiate this from 12345? It's actually not terribly difficult to do with a regular expression. The problem is actually one of performance. I can't really explain why this is in great detail, but it essentially boils down to the fact that differentiating 12345foobar from 12345 requires backtracking. This makes the regular expression non-deterministic.
The question is akin to asking why can't the King move four spaces at a time in Chess? It's because in Chess that is an illegal move. Can it in another game sure. It just depends on the rules being played by.
Originally it was simply because it is easier to remember (you can give it more meaning) variable names as strings rather than numbers although numbers can be included within the string to enhance the meaning of the string or allow the use of the same variable name but have it designated as having a separate, but close meaning or context. For example loop1, loop2 etc would always let you know that you were in a loop and/or loop 2 was a loop within loop1.Which would you prefer (has more meaning) as a variable: address or 1121298? Which is easier to remember?However, if the language uses something to denote that it not just text or numbers (such as the $ in $address) it really shouldn't make a difference as that would tell the compiler that what follows is to be treated as a variable (in this case).In any case it comes down to what the language designers want to use as the rules for their language.
print is a generic method that accepts all types of variable. so in that situation compiler does not know which (1) the programmer refers to : the 1 of integer value or the 1 that store a string value.maybe better for compiler in this situation to allows to define something like that but when trying to use this ambiguous stuff, bring an error with correction capability to how gonna fix that error and clear this ambiguity.
The names starting with name search tool lets you find names beginning with the letters that you specify in the Litscape Names list (over 144,359 names). Use the length filters if you want the resulting names constrained by length. Enter your starting letters. Click the Find Names button. If you enter more starting letters, fewer names will result. Fewer beginning letters will produce more names.
Tongue twisters are spoken word games in which a sequence of words is hard to say. Tongue twisters use a set of sounds, where the sounds in the words are repeated, but the order of the sounds is altered and the tongue must be repositioned to say them. They involve the use of alliteration and other rhyming schemes.
If you have a website and feel that a link to this page would fit in nicely with the content of your pages, please feel free to link to this page. Copy and paste the following html into your webpage. (You may modify the link text to suit your needs).
So let's say there are 500 columns in which that 100 of them are named S1_Something to S100_Something and the rest are named SOMETHING_Something to SOMETHING_Something. I want to perform a macro on all of the columns that start with S1-S100. So what I have so far is kind of an ugly way of doing it but it is
But instead of outputting the column into the log, I would then concatenate it into a macro variable and then shove that macro variable into a macro that will then loop over all of the strings inside the macro variable and perform the macro on that. So what I have should work however I was wondering if there was an easier way of doing it. Basically having an array of "S1"-"S100" and seeing if it is in that array but I don't believe that is possible. I wouldn't be able to do LIKE S% because it would also grab all of the columns that are like S% which is all of the columns and not just S1_Something - S100_Something.
Like the example that I had given, that code will grab all of the columns that start with "S" which would grab the columns SOMETHING1_something-SOMETHING400_something and notj ust S1_something-S100_something.
You can make like more complex though, even use REGEX if you want to make it super complicated. You're finding a lot of reasons why our solutions won't work for you. I really suggest explaining what you're doing in more detail at this point.