Write regular expressions to capture the following.

(a) Strings in C. These are delimited by double quotes ("), and may not contain newline characters. They may contain double-quote or backslash characters if and only if those characters are “escaped” by a preceding backslash. You may find it helpful to introduce shorthand notation to represent any character that is not a member of a small specified set.

(b) Comments in Pascal. These are delimited by (* and *) or by { and }. They are not permitted to nest.

(c) Numeric constants in C. These are octal, decimal, or hexadecimal integers, or decimal or hexadecimal floating-point values. An octal integer begins with 0, and may contain only the digits 0–7. A hexadecimal integer begins with 0x or 0X, and may contain the digits 0–9 and a/A–f/F. A decimal floating-point value has a fractional portion (beginning with a dot) or an exponent (beginning with E or e). Unlike a decimal integer, it is allowed to start with 0. A hexadecimal floating point value has an optional fractional portion and a mandatory exponent (beginning with P or p). In either decimal or hexadecimal, there may be digits to the left of the dot, the right of the dot, or both, and the exponent itself is given in decimal, with an optional leading + or - sign. An integer may end with an optional U or u (indicating “unsigned”), and/or L or l (indicating “long”) or LL or ll (indicating “long long”). A floating-point value may end with an optional F or f (indicating “float”—single precision) or L or l (indicating “long”—double precision).

(d) Floating-point constants in Ada. These match the definition of real in Example 2.3, except that (1) a digit is required on both sides of the decimal point, (2) an underscore is permitted between digits, and (3) an alternative numeric base may be specified by surrounding the non exponent part of the number with pound signs, preceded by a base in decimal (e.g., 16#6.a7#e+2). In this latter case, the letters a . . f (both upper- and lowercase) are permitted as digits. Use of these letters in an inappropriate (e.g., decimal) number is an error, but need not be caught by the scanner.

(e) Inexact constants in Scheme. Scheme allows real numbers to be explicitly inexact (imprecise). A programmer who wants to express all constants using the same number of characters can use sharp signs (#) in place of any lower-significance digits whose values are not known. A base-10 constant without exponent consists of one or more digits followed by zero of more sharp signs. An optional decimal point can be placed at the beginning, the end, or anywhere in-between. (For the record, numbers in Scheme are actually a good bit more complicated than this. For the purposes of this exercise, please ignore anything you may know about sign, exponent, radix, exactness and length specifiers, and complex or rational values.)

(f) Financial quantities in American notation. These have a leading dollar sign ($), an optional string of asterisks (*—used on checks to discourage fraud), a string of decimal digits, and an optional fractional part consisting of a decimal point (.) and two decimal digits. The string of digits to the left of the decimal point may consist of a single zero (0). Otherwise it must not start with a zero. If there are more than three digits to the left of the decimal point, groups of three (counting from the right)must be separated by commas (,). Example: $**2,345.67. (Feel free to use “productions” to define abbreviations, so long as the language remains regular.)