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Entire books (or at least large portions of book) have been written on lex. &nbsp;Let me suggest the O'Reilly &quot;lex and yacc&quot; book to help you with your homework problem.<br />
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<a href="http://www.oreilly.com/catalog/lex/" rel="ugc">http://www.oreilly.com/catalog/lex/</a>
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Entire books (or at least large portions of book) have been written on lex.  Let me suggest the O'Reilly "lex and yacc" book to help you with your homework problem.

http://www.oreilly.com/catalog/lex/ [http://www.oreilly.com/catalog/lex/]

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I asked this question just because I don't want to read the whole book inorder to do one simple thing.
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I asked this question just because I don't want to read the whole book inorder to do one simple thing.

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Yes, it would be awful if you actually had to learn something in order to do the work. &nbsp;Maybe some other expert will take pity on you and post a complete tutorial on using lex for 50 pts. but I doubt it.<br />
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Yes, it would be awful if you actually had to learn something in order to do the work.  Maybe some other expert will take pity on you and post a complete tutorial on using lex for 50 pts. but I doubt it.



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Many questions like the one I asked have short and clear answers and do not require reading the whole book.<br />
If you save a programmer time by answering his question he can use this time to learn the things that he really needs to know thoroughly.<br />
Do you want to help or to argue?
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Many questions like the one I asked have short and clear answers and do not require reading the whole book.
If you save a programmer time by answering his question he can use this time to learn the things that he really needs to know thoroughly.
Do you want to help or to argue?

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please explain me shortly how to use lex.<br />
I'm writing a calculator so what I have in my strings are operators and digits and functions with alphanumeric name.<br />
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10x alot.
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please explain me shortly how to use lex.
I'm writing a calculator so what I have in my strings are operators and digits and functions with alphanumeric name.

10x alot.

C is a general-purpose, imperative computer programming language, supporting structured programming, lexical variable scope and recursion, while a static type system prevents many unintended operations. By design, C provides constructs that map efficiently to typical machine instructions, so it has found lasting use in applications that had formerly been coded in assembly language, including operating systems as well as various application software for computers ranging from supercomputers to embedded systems. It is distinct from C++ (which has its roots in C) and C#, and many later languages have borrowed directly or indirectly from C.