Give a regular expression for a certain type of scientific n

Give a regular expression for a certain type of scientific notation for real numbers on which the following rules hold. Let sigma = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, \"+\", \"-\", e}. The number can be preceded by a \"+\" or \"-\" sign or the sign may be absent. Numeric values must be of the form cb_1 b_2 ... b_n where b_i is any digit, but c must be nonzero. The number may be followed by an exponent field of the form e\"+\" yy or e\"-\"yy, where y can be any digit.

Solution

The required regular expression is [+-]?[1-9]([0-9])*(e[+-]([0-9]){2})?

Note:

Square brackets [ ] is used to specify a list of possible choices of characters

? indicates optional

* indicates zero or many repetitions of the preceding group

round Brackets ( ) are used for grouping

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Let me explain with the requirements

1. number can be preceded by an optional + or - sign . This is done as [+-]?

2. numeric values in the form cbbbb... where c is nonzero is done as [1-9]([0-9])*

3. the optional exponent part of the form e followed by + or - and 2 digits is written as (e[+-]([0-9]){2})?

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