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# ArithExpr - Arithmetic Expressions in C Arithmetic...

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Arithmetic Expressions in C Arithmetic Expressions consist of numeric literals, arithmetic operators, and numeric variables. They simplify to a single value, when evaluated. Here is an example of an arithmetic expression with no variables: 3.14*10*10 This expression evaluates to 314, the approximate area of a circle with radius 10. Similarly, the expression 3.14*radius*radius would also evaluate to 314, if the variable radius stored the value 10. You should be fairly familiar with the operators + , - , * and /. Here are a couple expressions for you all to evaluate that use these operators: Expression Value 3 + 7 - 12 6*4/8 10*(12 - 4) Notice the parentheses in the last expression helps dictate which order to evaluate the expression. For the first two expressions, you simply evaluate the expressions from left to right. But, the computer doesn't ALWAYS evaluate expressions from left to right. Consider the following expression:

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3 + 4*5 If evaluated from left to right, this would equal (3+4)*5 = 35 BUT, multiplication and division have a higher order of precedence than addition and subtraction. What this means is that in an arithmetic expression, you should first run through it left to right, only performing the multiplications and divisions. After doing this, process the expression again from left to right, doing all the additions and subtractions. So, 3+4*5 first evaluates to 3+20 which then evaluates to 23. Consider this expression: 3 + 4*5 - 6/3*4/8 + 2*6 - 4*3*2 First go through and do all the multiplications and divisions: 3 + 20 - 1 + 12 - 24 Now, do all the additions and subtractions, left to right: 10 If you do NOT want an expression to be evaluated in this manner, you can simply add parentheses (which have the highest precendence) to signify which computations should be done first. (This is how we compute the subtraction first in 10*(12 - 4).) So, for right now, our precedence chart has three levels: parentheses first, followed by multiplication and division, followed by addition and subtraction.
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