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Processor Basics – Structure and Function
Published in Pranabananda Chakraborty, Computer Organisation and Architecture, 2020
Mathematical formulas are commonly expressed in what is known as infix notation where a binary operation appears between the operands (e.g. u+v). The arithmetic expressions can be represented in prefix notation where the operator is placed before the operands (e.g. +uv). This representation is often referred to as Polish notation. The postfix notation, referred to as reverse Polish notation (RPN), places the operator after the operands (e.g. uv+). It is to be noted that, regardless of the complexity of an expression, no parentheses are ever required while using RPN. This notation is ideal for evaluating arithmetic and other expressions on a computer which is stack-organised. The expression consists of n symbols, where each one is either an operand (variable or constant) or an operator. The procedure consists of first converting the arithmetic expression into its equivalent RPN using a suitable algorithm. The expression in RPN thus generated will then finally be evaluated by another algorithm using a stack.
Genetic Programming
Published in A Vasuki, Nature-Inspired Optimization Algorithms, 2020
When a tree is traversed using one of the above three techniques, the same traversal is repeatedly done for all the subtrees until the entire tree has been traversed. When the tree is a binary expression tree, the three traversals yield expressions in three different forms. The three types of traversals yielding prefix, infix, and postfix expressions are shown in Figure 5.7a, b and c respectively. PreOrder traversal yields prefix expression, InOrder traversal yields infix expression, and PostOrder traversal yields postfix expression. In prefixnotation, the operator appears before the operands. In infix notation, the operator appears between the operands. In postfix notation, the operator appears after the operands. As a simple example, consider the expression a*b, where the multiplication operator appears between the operands. This is the standard infix notation normally used in all the evaluations. In prefix notation, the expression becomes *ab, and in postfix notation, the expression becomes ab*. When the expressions are evaluated with values assigned to the variables, all three types produce the same result.
O
Published in Phillip A. Laplante, Dictionary of Computer Science, Engineering, and Technology, 2017
operator (1) a symbol in a programming language which specifies a computation. Traditionally operators represent arithmetic computations (with some common representations shown in parentheses) such as add (+), subtract (-), multiply (*), divide (/), or negation (-), logical computations such as and (&, .AND.), or ( 1, .OR.), or not (, .NOT.), comparison (<, >, =, ==, <=, >=, .LT., .GT., .EQ., .LE., .GE.), and assignment (= or :=). Languages may define many other operators, for example, C++ defines new and delete operators among many others. Traditional notations use infix notation for binary operators and prefix notation for unary operators, and maintain the traditional algebraic operator precedence to determine operand association; other languages use prefix notation or postfix notation, or may redefine operator hierarchy or declare all operators to have the same hierarchy.
Learning dispatching rules for single machine scheduling with dynamic arrivals based on decision trees and feature construction
Published in International Journal of Production Research, 2021
To represent the expression for constructing a new attribute, we implemented the postfix notation for chromosome representation proposed by Dabhi and Vij (2011). Unlike the infix notation, the postfix notation changes the position of the operators by moving them towards the right of the operands. In the case of postfix notation, stack can be used to transform a chromosome into an expression as shown in the below steps. Set the current gene to the start gene of a chromosome.Identify the type of the current gene. If the current gene represents an operand, go to Step 3; otherwise go to Step 4.Push the operand that represents an attribute on the stack and go to Step 5.Check whether there is the required number of operands in the stack. If the number of operands in the stack is not sufficient for the operator, mark the gene as ‘unused’ and go to Step 5; Otherwise, pop operands from the stack, combine operands and the operator into an intermediate expression, and push it on the stack.Set the next gene to the current gene and go to Step 2 until the current gene is the last gene of the chromosome.