Write a lex program that copies a file

When used as a preprocessor for a later parser generator, Lex is used to partition the input stream, and the parser generator assigns structure to the resulting pieces. Practice Problems Write a Lex program that copies a file, replacing each nonempty sequence of whitespace consisting of blanks, tabs, and newlines by a single blank.

This is a typical expression for recognizing identifiers in computer languages. Lex will recognize a small amount of surrounding context.

Such rules are often required to avoid matching some other rule which is not desired. The next rule copies continuation card indications to avoid confusing them with constants: This routine is also a convenient place to print tables, summaries, etc.

Additional programs, written by other generators or by hand, can be added easily to programs written by Lex. The function yyless might be used to reprocess text in various circumstances. This is explained further below. At present, the only supported host language is C, although Fortran in the form of Ratfor [2] has been available in the past.

It accepts a high-level, problem oriented specification for character string matching, and produces a program in a general purpose language which recognizes regular expressions.

Also, a character combination which is omitted from the rules and which appears as input is likely to be printed on the output, thus calling attention to the gap in the rules. This action is so common that it may be written as ECHO: The next rule copies continuation card indications to avoid confusing them with constants: Consider the following problem: Note that there is a default action, which consists of copying the input to the output.

Compatible run-time libraries for the different host languages are also provided. The declarations section can be empty. It may be objected that this program will alter such input items as There are three classes of such things.

Lex - A Lexical Analyzer Generator

Suppose that Liedtke's utility function is given by the utility function in Table Sometimes it is desirable to have several sets of lexical rules to be applied at different times in the input.

To do this, just return the minus sign as well as the letter to the input:. Write a Lex program that converts a file of English text to "Pig Latin." Assume the file is a sequence of words separated by whitespace.

If a word begins with a consonant, move the consonant to the end of the word and add "ay". Write a Lex program that copies a file, replacing each nonempty sequence of white space by a single blank.

Example program for the lex and yacc programs

2. Write a Lex program that copies a C program, replacing each instance of the keyword float by double. 3. In SQL, keywords and identifiers are case-insensitive. Write a Lex program that converts a file of English text to "Pig Latin." Assume the file is a sequence of words separated by whitespace.

If a word begins with a consonant, move the consonant to the end of the word and add "ay". The generated program is on a file named douglasishere.comc. The I/O library is defined in terms of the C standard library [6].

The C programs generated by Lex are slightly different on OS/, because the OS compiler is less powerful than the UNIX or GCOS compilers, and does less at compile time.

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May 14,  · 1)write a lex program that copies a file,replacing each nonnull sequence of white space by a single blank. 2)what is the input alphabet of the languages pascal,ada,lisp and fortran 77?Status: Resolved. Write a Lex program that copies a C program, replacing each instance of the keyword float by double - Home» Questions» Finance» Risk Management» Risk Management Techniques» Write a Lex program that copies a C program.

Write a lex program that copies a file
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