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{SECT 0 {PARA 18 "" 0 "" {TEXT -1 22 "Assignment Expressions" }}{PARA 
0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 53 "This worksheet \+
is designed to accompany Chapter 3 of " }{TEXT 256 87 "Introduction to
 Scientific Programming: Computational Problem Solving Using Maple and
 C" }{TEXT -1 127 " by Joseph L. Zachary.  In it, we will use Maple to
 explore operator precedence and assigment statements in  Maple (AW, J
an 97)" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{SECT 1 {PARA 3 "" 0 "" 
{TEXT -1 10 "Assignment" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 193 "When a
 number is used several times in a worksheet, it is better to assign a
 name to that number, rather than retyping it on every occasion.  This
 eliminates errors and speeds up your workrate." }}{PARA 0 "" 0 "" 
{TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 221 "For example, suppose we \+
are doing computations that involve the population of the earth like w
e did in Chapter 2.  Rather than typing the number 5.761e9 every time \+
it is used, we can assign its value to a variable, say P:" }}{PARA 0 "
" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 13 "P := 5.761e9
;" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 
60 "Similarly, we can assign the land area to a variable, say A:" }}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 12 "A :
= 57.8e6;" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" 
{TEXT -1 167 "The variables A and P will now retain these values for f
urther computations in this worksheet.  For example,  we can  compute \+
the number of persons per square mile as " }}{PARA 0 "" 0 "" {TEXT -1 
0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 4 "P/A;" }}}{PARA 0 "" 0 "" 
{TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 82 "Or we could comput
e the side length of the square (in feet) that each of us get by" }}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 17 "528
0 * sqrt(A/P);" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 
0 "" {TEXT -1 148 "Note that the colon that precedes the equal to sign
 is an essential part of  the assignment statement; it cannot be ignor
ed.  Execute the assignment" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 
0 "> " 0 "" {MPLTEXT 1 0 13 "B = 14.56e-1;" }}}{PARA 0 "" 0 "" {TEXT 
-1 0 "" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 26 "followed by the expressi
on" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 
4 "2*B;" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" 
{TEXT -1 132 "That did not help much did it?   Now insert the  colon r
ight before the equals sign and reevaluate these two expressions.    B
etter?" }}}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{SECT 1 {PARA 3 "" 0 "" 
{TEXT -1 23 "Choosing Variable Names" }}{EXCHG {PARA 0 "" 0 "" {TEXT 
-1 352 "It is a good strategy to pick descriptive names that you can q
uickly recall.  For example,  suppose we need to solve the population \+
density problem of Chapter 2 for the planets Mars and Venus (assuming \+
a means of sustaining the entire population of the earth on these plan
ets has been found.)    Then it will be good to name these variables a
s follows:" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" 
{MPLTEXT 1 0 55 "Aearth := 57.8e6;  Amars := 56.0e6;  Avenus := 177.7e
6;" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 
-1 63 "(Note how several expressions can be entered on the same line.)
" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 192 "Now \+
return to the expressions P/A and 5280*sqrt(A/P) above.   Re-execute t
hem, with the appropriate variable inserted in place of A, to solve th
e population density problem for Mars and Venus." }}}}{PARA 0 "" 0 "" 
{TEXT -1 0 "" }}{SECT 1 {PARA 3 "" 0 "" {TEXT -1 15 "Special Symbols" 
}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 161 "There are a few symbols that ha
ve a pre-defined meaning in Maple that you may not use as variable nam
es.  Maple will warn you should you transgress.  For example" }}{PARA 
0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 8 "Pi := 3;" 
}}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 
109 "The problem is that the symbol Pi is reserved for the mathematica
l constant 3.14159...  If you evaluate this," }}{PARA 0 "" 0 "" {TEXT 
-1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 10 "evalf(Pi);" }}}{PARA 0 "
" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 40 "You will se
e the first ten digits of Pi." }{MPLTEXT 1 0 0 "" }}{PARA 0 "" 0 "" 
{TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 56 "Observe how you can use G
reek letters as variable names:" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{PARA 0 "> " 0 "" {MPLTEXT 1 0 11 "alpha := 1;" }}{PARA 0 "" 0 "" 
{TEXT -1 0 "" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 
0 "" {MPLTEXT 1 0 13 "omega := 100;" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" 
}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 11 "pi := 22/7;" }}}{PARA 0 "
" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 264 "Notice the
 difference between this pi and the Pi above.  The lower case pi is si
mply the Greek letter for p, with no special meaning attached to it.  \+
The upper case Pi, on the other hand, stands for the ratio between the
 circumference of a circle and its diameter." }{MPLTEXT 1 0 0 "" }}}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 158 "A
 useful built-in Maple variable is Digits.  It allows you to specify t
he mantissa length for floating-point computations.  The default value
 of Digits is 10." }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "
" {MPLTEXT 1 0 7 "Digits;" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG 
{PARA 0 "" 0 "" {TEXT -1 51 "So a ten-digit computation of 10/3 looks \+
like this:" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" 
{MPLTEXT 1 0 12 "evalf(10/3);" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{EXCHG {PARA 0 "" 0 "" {TEXT -1 31 "If we set Digits to 2, however," }
}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 12 "Di
gits := 2;" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" 
{TEXT -1 36 "We get a result with only two digits" }}{PARA 0 "" 0 "" 
{TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 12 "evalf(10/3);" }}}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 27 "an
d if we set Digits to 30," }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "
> " 0 "" {MPLTEXT 1 0 13 "Digits := 30;" }}}{PARA 0 "" 0 "" {TEXT -1 
0 "" }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 31 "we get a result with 30 dig
its." }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 
0 12 "evalf(10/3);" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 
"" 0 "" {TEXT -1 7 "Now try" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 
0 "> " 0 "" {MPLTEXT 1 0 12 "Digits := 2;" }}}{PARA 0 "" 0 "" {TEXT 
-1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 8 "999 - 1;" }}}{PARA 
0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 10 "99
9. - 1.;" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "" 0 "" 
{TEXT -1 47 "Explain the difference between the two answers." }}{PARA 
0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 209 "When you exper
iment with changing the value of Digits, always be sure to reset its v
alue to the default value of 10 before continuing.  Otherwise, you may
 get some unpleasant surprises later in your worksheet." }}{PARA 0 "" 
0 "" {TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 13 "Digits := 10;
" }}}}}{MARK "0 0" 0 }{VIEWOPTS 1 1 0 1 1 1803 }