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Posted 19 Aug 2006

# Create Postfix from infix experssion.

, 19 Aug 2006
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## Introduction

Ali reza zareian.

This is a simple program that creates postfix expression from an infix expression. What is an infix expression?<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p>

<o:p>

(a+b)/d is a simple one. The infix expression is regular for mathematic. it means when u want to calculate this u must<o:p>

Add a with b at the first time then divided with d.<o:p>

If  we change this expression to postfix. We have this one ab+d/.<o:p>

What is the useful of postfix?<o:p>

At first we don't need parantes.Second we can write a program to calculate this expression easier than infix expression.<o:p>

<o:p>

What is this program?<o:p>

This programe use a simple algoritm to change infix to postfix.Just sees the example<o:p>

Before I should say I use stack in this program.<o:p>

<o:p>

Infix Program =(a+b)/d  <o:p>

<o:p>

<o:p>

Input     Stack        output<o:p>

(             (<o:p>

a            (                     a<o:p>

+           (+                   a<o:p>

b           (+                   ab<o:p>

)                                  ab+<o:p>

/            /                     ab+<o:p>

d                                 ab+d<o:p>

No         empty           ab+d/<o:p>

<o:p>

<o:p>

Main method of this program!?

1)      private int isOperand(char  chrTemp);

2)      private int isOperator(char chrTemp);

3)      public string createPrifex();

<o:p>

<o:p>

1) isOperand check character if they are in this set.{'*','/','+','-','^','('}

If true we add this character to stack.

<o:p>

2)isOperator check character if they are in this set.{'*','/','+','-','^'}

This  method check the  stack  and  pop all the operator except '('.

<o:p>

3)createPrifix method create postfix from infix use isOperand and isOperator.

<o:p>

PesoCode

For (the first infix character ) to  last character

{

If  (is operand)   add to stack

Elae

If  (it is ')' )   pop  stack and send it to output

Else send other character to output

}

<o:p>

}

<o:p>

<o:p>

<o:p>

<o:p>

<o:p>

<o:p>

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