Perl array variables are prefixed by the at sign (@). In addition, all Perl variable names must follow these rules:
- Variable names must contain only letters (a-z, A-Z), underscores (_), and numeric digits (0-9).
- The first character of a variable name must be a letter (a-z, A-Z) or underscore (_).
- Variable names are case-sensitive, so myvariable is not the same as MyVariable.
Some variable names are used by WebAssign. These variables are listed in the documentation.
One-Dimensional Arrays
One-dimensional arrays are like grocery lists. For example:
wine cheese bread
In Perl, you enclose the list in parentheses and separate individual list items with commas. For example:
@groceries = ('wine', 'cheese', 'bread');To refer to a single element in the array, specify the array variable as a scalar with an index indicating which element you are referring to. The index starts with 0 and follows the variable name in brackets. For example:
The second item on my grocery list is <eqn $groceries[1]>.You can mix numeric and text data in an array.
Two-Dimensional Arrays
Two-dimensional arrays let you work with tabular data. For example:
Mercury | 0.39 |
Venus | 0.72 |
Earth | 1 |
Mars | 1.52 |
Jupiter | 5.20 |
Saturn | 9.54 |
Uranus | 19.18 |
Neptune | 30.06 |
In Perl, you enclose the entire table in parentheses, enclose each row in brackets, and separate both rows and table cells with commas. For example:
@dat = ( ['Mercury' , 0.39 ],
['Venus' , 0.72 ],
['Earth' , 1 ],
['Mars' , 1.52 ],
['Jupiter' , 5.20 ],
['Saturn' , 9.54 ],
['Uranus' , 19.18],
['Neptune' , 30.06] );To refer to an element in a two-dimensional array, specify the array variable as a scalar with two indexes indicating the row and column of the element you are referring to. The index values start with 0 and follow the variable name in brackets. For example:
The average distance from the Sun to <eqn $dat[4][0]> is <eqn $dat[4][1]> AU.The @dat Array
WebAssign provides support for viewing one- and two-dimensional array values in the Question Previewer when you use an array named @dat. If your question contains the @dat array, the Question Previewer displays an additional tab named Array, which displays the contents of the array in addition to the question code and a preview of your question.
In all other respects, the @dat array is a normal array and can contain whatever values you want.
In an <EQN> or <eqn> tag, set the values for elements of the array using assignment statements like the following examples.
@planets = ('Mercury', 'Venus', 'Earth', 'Mars', 'Jupiter', 'Saturn', 'Uranus', 'Neptune'); @mean_au = (0.39, 0.72, 1, 1.52, 5.20, 9.54, 19.18, 30.06); @dat = ( ['Mercury' , 0.39 ], ['Venus' , 0.72 ], ['Earth' , 1 ], ['Mars' , 1.52 ], ['Jupiter' , 5.20 ], ['Saturn' , 9.54 ], ['Uranus' , 19.18], ['Neptune' , 30.06] ); $dwarf_planets[0] = 'Pluto'; $dwarf_planets[1] = 'Eris';In an <EQN> or <eqn> tag, reference specific array element values by specifying the array variable as a scalar with an index indicating which element you are referring to, as in the following examples.
$thisplanet = $planets[7]; # sets $thisplanet = Neptune $thismean_au = $mean_au[7]; # sets $thismean_au = 30.06 $firstplanet = $dat[0][0]; # sets $firstplanet = Mercury $firstorbit = $dat[0][1]; # sets $firstorbit = 0.39
Example Question Using Array to Define Possible Answers The following table summarizes an actual question. QID Name Mode Fill-in-the-Blank Question <eqn> @dat= ('John Lennon', 'Paul McCartney', 'George Harrison', 'Ringo Starr'); '' </eqn> Name one of the Beatles: <_> Answer <EQN join("\t",@dat)> Display to Students 
Example Question Using Array and Randomization The following table summarizes an actual question. QID 1950001 Name Template2 RAND.ARRAY Mode Multiple-Choice Question Answer Display to Students 