Chapter 2: Problem 1
For an integer \(r \in \mathbb{N}_{>1}\), we consider the variable-length radix
\(r\) representation \(\left(a_{0}, \ldots, a_{l-1}\right) 0\) a positive integer
\(a\), with \(a=\sum_{0 \leq i
Short Answer
Expert verified
The length of the radix representation is \(\lfloor \log_r a \rfloor + 1\).
Step by step solution
01
Understanding the Problem
We need to show that the length of the radix-\(r\) representation of an integer \(a\), noted as \(l\), is equal to $$\(\lfloor\log _{r} a\rfloor+1\). The radix representation consists of coefficients \(a_0, a_1, \ldots, a_{l-1}\), each between \(0\) and \(r-1\), for base \(r\), representing the integer \(a\) as a sum \(a = a_0 r^0 + a_1 r^1 + \cdots + a_{l-1} r^{l-1}\).
02
Express the Problem with Logarithm
Express the integer \(a\) in terms of its polynomial representation: \(a = a_0 r^0 + a_1 r^1 + \cdots + a_{l-1} r^{l-1}\). Since \(a_{l-1} eq 0\), \(a \geq r^{l-1}\). To maintain integrality, we have \(a < r^l\) if \(l\) is the least possible number of digits for the radix \(r\) representation.
03
Set Bounds Using Inequalities
From Step 2, we have \(r^{l-1} \leq a < r^l\). Taking the logarithm base \(r\) on all sides, $$we obtain the inequalities \(l-1 \leq \log_r a < l\). Since \(l\) is an integer, \(l = \lfloor \log_r a \rfloor + 1\) gives the shortest valid length \(l\) for the radix representation of \(a\).
04
Proving the Equation
The inequality \(l-1 \leq \log_r a < l\) implies the length \(l\) is the smallest integer greater than \(\log_r a\). Consequently, we can write \(l = \lfloor \log_r a \rfloor + 1\), which means the length of the variable-length radix-\(r\) representation is indeed this value.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Integer Representation
Integer Representation is a method of describing numbers using a specified numerical system or base, known as a radix. In a radix-r representation, a number a is expressed as a sum of terms. Each term is a digit multiplied by a power of the base r. This can be written as:
For example, in the decimal system (r = 10), the number 345 is represented as 3 hundreds, 4 tens, and 5 units. Thus, understanding integer representation across different bases is essential for grasping Radix Representation.
- \( a = a_0 r^0 + a_1 r^1 + \cdots + a_{l-1} r^{l-1} \)
For example, in the decimal system (r = 10), the number 345 is represented as 3 hundreds, 4 tens, and 5 units. Thus, understanding integer representation across different bases is essential for grasping Radix Representation.
Logarithmic Functions
Logarithmic functions play a pivotal role in determining the length of a number's representation in different bases. The logarithm base r of a number a, expressed as log_r a, gives power to which base r must be raised to produce a.
More formally:
More formally:
- The equation \(r^l = a\) implies \(l = log_r a\)
- The inequality \(l - 1 \leq log_r a < l\) is arranged.
Base Conversion
Base conversion is the process of changing a number from one base to another. Understanding Radix Representation is particularly useful in base conversion.
The number a in base r is represented as:
For example, to convert number 345 from base 10 to base 2, divide the number repeatedly by 2, recording remainders - these form the binary equivalent when read backward. Base conversion empowers us to work fluently across different systems.
The number a in base r is represented as:
- \( a = a_0 r^0 + a_1 r^1 + \cdots + a_{l-1} r^{l-1} \)
For example, to convert number 345 from base 10 to base 2, divide the number repeatedly by 2, recording remainders - these form the binary equivalent when read backward. Base conversion empowers us to work fluently across different systems.
Mathematical Proof
Mathematical proof involves constructing a logical argument that shows the truth of a given statement using established mathematical principles. Here, we have proved the representation length using inequalities and logarithmic identities.
The proof captures several foundational components:
The proof captures several foundational components:
- Identifying the upper and lower bounds with potentials like \(r^{l-1} \leq a < r^l\)
- Taking the logarithm base r to obtain \(l-1 \leq log_r a < l\)
- Simplifying result to find \(l = \lfloor log_r a \rfloor + 1\), the desired representation length.