Expressions - Revision history

Admin: Replacing charlesreid1.com:3000 with git.charlesreid1.com

2019-10-09T03:24:01Z

Replacing charlesreid1.com:3000 with git.charlesreid1.com

← Older revision		Revision as of 03:24, 9 October 2019
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	To analyze and evaluate thees kinds of expressions, we often want to build an expression tree. Here is some pseudocode for two algorithms for building postfix and infix expression trees, plus a link to Java code that does this:		To analyze and evaluate thees kinds of expressions, we often want to build an expression tree. Here is some pseudocode for two algorithms for building postfix and infix expression trees, plus a link to Java code that does this:

	Expression trees git.charlesreid1.com link: https://charlesreid1.com~~:3000~~/cs/java/src/master/trees/expressions		Expression trees git.charlesreid1.com link: https://git.charlesreid1.com/cs/java/src/master/trees/expressions

	Postfix expression tree builder code: https://charlesreid1.com~~:3000~~/cs/java/src/master/trees/expressions/PostfixExpressionTree.java		Postfix expression tree builder code: https://git.charlesreid1.com/cs/java/src/master/trees/expressions/PostfixExpressionTree.java

	'''Postfix expression tree builder:'''		'''Postfix expression tree builder:'''
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	The corresponding infix expression builder pseudocode follows.		The corresponding infix expression builder pseudocode follows.

	Infix expression builder code: https://charlesreid1.com~~:3000~~/cs/java/src/master/trees/expressions/InfixExpressionTree.java		Infix expression builder code: https://git.charlesreid1.com/cs/java/src/master/trees/expressions/InfixExpressionTree.java

	'''Infix expression tree builder:'''		'''Infix expression tree builder:'''

Admin at 06:43, 8 July 2017

2017-07-08T06:43:32Z

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 Two main kinds of expressions that you see:
 * postfix expressions (a.k.a. reverse polish notation)
@@ Line 88: / Line 90: @@
 </pre>

Admin: /* Algorithms */

2017-07-08T06:42:46Z

Algorithms

← Older revision		Revision as of 06:42, 8 July 2017
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	The corresponding infix expression builder pseudocode follows.		The corresponding infix expression builder pseudocode follows.

			Infix expression builder code: https://charlesreid1.com:3000/cs/java/src/master/trees/expressions/InfixExpressionTree.java

	'''Infix expression tree builder:'''		'''Infix expression tree builder:'''

Admin: /* Algorithms */

2017-07-08T06:42:25Z

Algorithms

← Older revision		Revision as of 06:42, 8 July 2017
Line 21:		Line 21:
	To analyze and evaluate thees kinds of expressions, we often want to build an expression tree. Here is some pseudocode for two algorithms for building postfix and infix expression trees, plus a link to Java code that does this:		To analyze and evaluate thees kinds of expressions, we often want to build an expression tree. Here is some pseudocode for two algorithms for building postfix and infix expression trees, plus a link to Java code that does this:

	git.charlesreid1.com link:		Expression trees git.charlesreid1.com link: https://charlesreid1.com:3000/cs/java/src/master/trees/expressions

			Postfix expression tree builder code: https://charlesreid1.com:3000/cs/java/src/master/trees/expressions/PostfixExpressionTree.java

	'''Postfix expression tree builder:'''		'''Postfix expression tree builder:'''
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	</pre>		</pre>

	~~and the~~ corresponding infix expression builder pseudocode follows.		The corresponding infix expression builder pseudocode follows.



	'''Infix expression tree builder:'''		'''Infix expression tree builder:'''

Admin: /* Algorithms */

2017-07-08T06:32:49Z

Algorithms

← Older revision		Revision as of 06:32, 8 July 2017
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	<pre>		<pre>
			create new node stack
			set start new expression to true
			while next char in expression:
			take next char
			if numeric:
			make new node
			if start new expression:
			push node onto stack
			set start new expression to false
			else if expression on stack:
			peek at top of stack
			if top of stack is operator:
			if top of stack has 1 child:
			add right child
			else:
			error
			else:
			error
			if operator:
			new node
			pop stack
			set node left to popped item
			push node onto stack
			if (:
			set start new expression to true
			if ):
			if stack size > 1:
			pop top of stack
			peek top of stack
			set popped item to peek's right

			while stack size > 1:
			pop top
			peek top of stack
			set popped item to peek's right

	</pre>		</pre>

Admin at 06:28, 8 July 2017

2017-07-08T06:28:55Z

@@ Line 15: / Line 15: @@
 <pre>
 ((5+4)*(8-3))/15
 </pre>

Admin: Created page with "Two main kinds of expressions that you see: * postfix expressions (a.k.a. reverse polish notation) * infix expressions (a.k.a. what we use all the time) A postfix expression..."

2017-07-08T02:41:58Z

Created page with "Two main kinds of expressions that you see: * postfix expressions (a.k.a. reverse polish notation) * infix expressions (a.k.a. what we use all the time) A postfix expression..."

New page

Two main kinds of expressions that you see:
* postfix expressions (a.k.a. reverse polish notation)
* infix expressions (a.k.a. what we use all the time)

A postfix expression looks like:

<pre>
5 4 + 8 3 - * 15 /
</pre>

which, when analyzed left to right, means take 5 and 4 and add them, to get 9, then take 8 and 3 and subtract them, to get 5, and then take the 9 and the 5 and multiply them, to get 45, and then take the 45 and the 15, and divide them to get 3.

This same expression would be written with infix notation, with parentheses, like so:

<pre>
((5+4)*(8-3))/15
</pre>