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Chapter 3: Problem 1

The backslash is itself a meta-character. Suppose that you want to match a string that contains a backslash character. How do you suppose you would represent the backslash in the regular expression?

Short Answer

Expert verified
To represent a backslash in a regular expression, it should be written as '\\'.

Step by step solution

01

Understanding the nature of a backslash in regex

It's important to note that the backslash is a special character in regular expressions. Being a meta-character, it has special uses such as initiating escape sequences. So, to represent a backslash in a string using regular expression, it can't just be placed directly in the expression.
02

Representing the backslash

A backslash can be represented in a regular expression by using a double backslash, i.e., '\\'. The first backslash acts as an escape character for the second backslash, yielding a single backslash in the resulting string.
03

Confirming the solution

To verify, one could use this form in a regular expression and test it on a string that contains a backslash. The expression should match any instances of a single backslash in the tested string.

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Most popular questions from this chapter

A function \(f(\alpha)\) is nonzero only in the region of width \(2 \delta\) centered at \(\alpha=0\) $$ f(\alpha)=\left\\{\begin{array}{ll} C & |\alpha| \leq \delta \\ 0 & |\alpha|>\delta \end{array}\right. $$ where \(C\) is a constant. (a) Find and plot versus \(\beta\) the Fourier transform \(A(\beta)\) of this function. (b) The function \(f \alpha\) ) might represent a pulse occupying either finite distance \((\alpha=\) position) or finite time \((\alpha\) = time). Comment on the wave number spectrum if \(\alpha\) is position and on the frequency spectrum if \(\alpha\) is time. Specifically address the dependence of the width of the spectrum on \(\delta\).

A photon has the same momentum as an electron moving at \(10^{6} \mathrm{~m} / \mathrm{s}\). (a) Determine the photon's wavelength \(\mathrm{N}\). (b) What is the ratio of the kinetic energies of the two?

The average intensity of an electromagnetic wave is \(\frac{1}{2} s_{0} c E_{0}^{2}\). where \(E_{0}\) is the amplitude of the electric-field portion of the wave. Find a general expression for the photon flux \(j\) (measured in photons/s \(-m^{2}\) ) in terms of \(E_{0}\) and wavelength \(\lambda .\)

At what wavelength does the human body emit the maximum electromagnetic radiation? Use Wien's law from Exercise 14 and assume a skin temperature of \(70^{\circ} \mathrm{F}\).

Show that the laws of momentum and enargy corservadion forbid the complete absorprion of a photon by a free electron. (Note: This is not the photoelectric effect In the pholoelectric effect, the electron is not free: the metal participates in momentum and eoergy onservation.)
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