COMS 6100 Class Notes

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1 COMS 6100 Class Notes Wenbo Dong 20 October Perl There is more than one way to do it. 1.1 Array 1,item 2,item is the beginning of an array. array stores scaler (beginning with $) example: = (1, 1, 2, 3, 5, 8, 13); = ( apples, bananas, strawberries, jack fruit, star fruit, mangos ); = (100, A++, Great Job! ); class demo: index print fruits[1]: \$fruits[1]\n ; # bananas print ; # displays all of the contents, each one separated by a space note: the index of array starts from class demo: types of index print The last fruit in the list is $fruits[ $#fruits ]\n ; # mangos print The last fruit in the list is $fruits[ -1 ]\n ; # mangos print( There are. ($#fruits + 1). fruits\n ); # 6 1

2 1.1.3 class question can we combine number with string? yes, we can class demo: add element to array $fruits[ 6 ] = Spondias mombin ; # add Spondias mombin as the 6th element $fruits[ 3 ] = jaca ; note: if define an 100th element, Perl will work but will give many errors before the 100th element class demo: assign value to array 1. (value, value, value...) 2. qw operator = ew(blue white); print ; note: in qw, is needed for separated words 3... operator: it fills numbers in between the numbers = (2, 3, 4, 6..9); # 6..9 means use an array = things... ); memory management the memory for array will dynamically grow and shrink so there will not be array out of bounds error array can be = (); built-in functions for changing array shift: Remove the first element (and shift everything down one index) unshift: Adds a new first element (and shift everything up one index) pop: Remove the last element push: Adds a new last element 2

3 1.1.8 class demo: memory management and built-in = qw(banana orange); # banana = (); # = qw(guava apple watermelon); # guava apple watermelon print ; # guava apple watermelon tomato ; print (after unshift)\n ; # tomato guava apple watermelon my $veggie = print Is $veggie a fruit or not?\n ; # tomato print (after shift)\n ; # guava apple watermelon grape ; # adds grape to the end of the array print (after push)\n ; #guava apple watermelon grape my $juice = # grape array slicing You can slice an array for a sub-array. small note: $array[0] is a is an array with one elemtne class demo: array slicing = qw(guava apple watermelon mango grape strawberry cranberry blueberry); 1,3 ]; print ; # guava watermelon ]; print ; # strawberry cranberry blueberry class exercise 1. Initialize a local array named favorites with the colors that you like the most. = qw(orange grey); 2. Add your preferred breakfast to the front of favorites. oatmeal ; 3. Add your preferred dessert to the back of favorites. pumpkin pie ; 3

4 4. Remove the first element from favorites and store it in a local scalar named breakfast. my $breakfast = 5. Remove the last element from favorites and store it in a local scalar named treat. my $treat = 1.2 Loop As a beginning, the loop will actually be covered in depth in the future classes. foreach my $fruit (@fruits){ print Would like some $fruit juice\n ; } 1.3 Hashes Array stores multiple values (scalers), organized by index; Hash stores multiple values (scalers), organized by keys or key-value pairs. Hashes start with % We make hash local scope by initializing with my Syntax: Hash: %hashname Value: $hashname{$key} class demo: syntax my \%wheels = (unicycle => 1, bike => 2, tricycle => 3, car => 4, semi => 18); print A car has $wheels{car} wheels\n ; # 4 print A bike has $wheels{bike} wheels (before adding training wheels)\n ; # 2 $wheels{bike} = $wheels{bike} + 2; print A bike has $wheels{bike} wheels (after adding training wheels)\n ; # 4 my %desserts = ( pie, apple, cake, carrot, sorbet, orange ); my %ice cream = (bowl => chocolate, float => root beer ); my %choices = (%desserts, %ice cream, healthy, salad ); # flattens the hashes print I would like some $choices{healthy} for lunch\n ; # salad 4

5 1.3.2 class exercise 1. Initialize a local hash named favorites with everyone s preferred color (names are keys, colors are values). my %favorites = ( Dr. C => blue, Gabriel => green ); 2. Store your preferred color into a scalar named background. my $background = $favorites Dr. C ; 3. Update your preferred color. $favorites{ Dr. C } = MTSU blue ; 4. Store a copy of all of the people into an array named names. = keys %favorites; 5. Store a copy of all of the colors into an array named colors. = values %favorites; 6. Remove Dr. Carroll s entry from the hash. delete $favorites{ Dr. C }; 5

MHealthy Approved Menu Items

MHealthy Approved Menu Items Calories Fat Cereals and Bread Products MHealthy Approved s at least 2. 1 gram 48 mg Barry's Sunny Grain Bagel 4 ozw 29 3 n/a n/a 4 6 3 6 11 Quaker Oatmeal Medley- Summer Berry 1 each 2 3. 2 1 7 14 8 Chips,