[system] / trunk / pg / macros / contextIntegerFunctions.pl Repository: Repository Listing bbplugincoursesdistsnplrochestersystemwww

# View of /trunk/pg/macros/contextIntegerFunctions.pl

Thu Jun 28 01:55:03 2007 UTC (12 years, 6 months ago) by dpvc
File size: 1537 byte(s)
```Updated to use the new context copy method.
```

```    1 loadMacros('Parser.pl');
2
3 sub _contextIntegerFunctions_init {}; # don't reload this file
4
6
7 ######################################################################
8 #
9 #  This is a Parser context that adds integer related functions C(n,r)
10 #  and P(n,r).  They can be used by the problem author and also by
11 #  students if the answer checking is done by Parser.  The latter is
12 #  the main purpose of this file.
13 #
14 #  Note: by default, webwork problems do not permit students to use
15 #        C(n,r) and P(n,r) functions.  Problems which do permit this
16 #        should alert the student in their text.
17 #
18 #  Usage examples:
19 #     \$b = random(2, 5); \$a = \$b+random(0, 5);
20 #     \$c = C(\$a, \$b);
21 #     ANS(Compute("P(\$a, \$b)")->cmp);
22 #
23 #  Note: If the context is set to something else, such as Numeric, it
24 #        can be set back with Context("IntegerFunctions").
25
26 =cut
27
28 \$context{IntegerFunctions} = Parser::Context->getCopy(undef,"Numeric");
29
30 package IntegerFunction2;
31 our @ISA = qw(Parser::Function::numeric2); # checks for 2 numeric inputs
32
33 sub C {
34   shift; my (\$n,\$r) = @_; my \$C = 1;
35   return (0) if(\$r>\$n);
36   \$r = \$n-\$r if (\$r > \$n-\$r); # find the smaller of the two
37   for (1..\$r) {\$C = (\$C*(\$n-\$_+1))/\$_}
38   return \$C
39 }
40
41 sub P {
42   shift; my (\$n,\$r) = @_; my \$P = 1;
43   return (0) if(\$r>\$n);
44   for (1..\$r) {\$P *= (\$n-\$_+1)}
45   return \$P
46 }
47
48 package main;
49