--- loncom/html/adm/help/tex/Problem_LON-CAPA_Functions.tex	2012/01/03 21:56:35	1.23
+++ loncom/html/adm/help/tex/Problem_LON-CAPA_Functions.tex	2013/10/18 03:43:14	1.27
@@ -65,8 +65,8 @@ Option 4 - @all = \&languages($\backslas
 \&roundto(\$x,\$n)  & Rounds a real number to n decimal points. \$x and \$n can be pure numbers \\
 \hline
  
-\&cas(\$s,\$e,\$l)&Evaluates the expression \$e inside the symbolic algebra system \$s. Currently, only the Maxima symbolic math system is implemented. 
-\$l is an optional comma-separated list of libraries. Example: \&cas('maxima','6*7')\\ 
+\&cas(\$s,\$e,\$l)&Evaluates the expression \$e inside the symbolic algebra system \$s. Currently, the Maxima symbolic math system ('maxima') and the R statistical computing system ('R') are implemented. 
+\$l is an optional comma-separated list of libraries. Example: \&cas('maxima','diff(sin(x)/cos(x),x,2)')\\ 
 \hline 
 
 \&implicit\_multiplication(\$f)&Adds mathematical multiplication operators to the formula expression \$f where only implicit multiplication is used. Example: \&implicit\_multiplication('2(b+3c)') returns 2*(b+3*c) \\
@@ -84,7 +84,7 @@ Option 4 - @all = \&languages($\backslas
 \&y0(\$x), \&y1(\$x), \&yn(\$m,\$x), \&yv(\$y,\$x)  & Bessel functions of the second kind with orders 0, 1 and m respectively. For yn(m,x), m must be an integer whereas for yv(y,x), y is real. \$x can be a pure number. \$m must be an integer and can be a pure integer number. \$y can be a pure real number \\
 \hline
  
-\&random(\$l,\$u,\$d)  & Returns a uniformly distributed random number between the lower bound, l and upper bound, u in steps of d. \$l, \$u and \$d can be pure numbers \\
+\&random(\$l,\$u,\$d)  & Returns a uniformly distributed random number between the lower bound, l and upper bound, u in steps of d. d is optional. If omitted, a step of 1 is used. \$l, \$u and \$d can be pure numbers. \\
 \hline
  
 \&choose(\$i,...)  & Choose the ith item from the argument list. i must be an integer greater than 0 and the value of i should not exceed the number of items. \$i can be a pure integer \\
@@ -133,7 +133,7 @@ Option 1 - \&map(\$seed,[$\backslash$\$w
  
 \&name(), \&student\_number(), \&firstname(), \&middlename(), \&lastname()  & Return the full name in the following format: lastname, firstname initial. Student\_number returns the student 9-alphanumeric string. The functions firstname, middlename, and lastname return just that part of the name. If undefined, the functions return null. \\
 \hline
-\&check\_status(\$partid) &Returns a number identifying the current status of a part. True values mean that a part is ``done'' (either unanswerable because of tries exhaustion, or correct) or a false value if a part can still be attempted. If \$part is unspecified, it will check either the current $<$part$>$'s status or if outside of a $<$part$>$, check the status of previous $<$part$>$. The full set of return codes are: 'undef' means it is unattempted, 0 means it is attempted and wrong but still has tries, 1 means it is marked correct, 2 means they have exceed maximum number of tries, 3 means it after the answer date.\\
+\&check\_status(\$partid) &Returns a number identifying the current status of a part. True values mean that a part is ``done'' (either unanswerable because of tries exhaustion, or correct) or a false value if a part can still be attempted. If \$part is unspecified, it will check either the current $<$part$>$'s status or if outside of a $<$part$>$, check the status of previous $<$part$>$. The full set of return codes are: 'undef' means it is unattempted, 0 means it is attempted and wrong but still has tries, 1 means it is marked correct, 2 means they have exceeded maximum number of tries, 3 means it is after the answer date.\\
 \hline
 \&open\_date(\$partid), \&due\_date(\$partid), \&answer\_date(\$partid)  & Problem open date, due date and answer date in local human-readable format.  Part 0 is chosen if \$partid is omitted.\\
 \hline
@@ -240,3 +240,13 @@ undef @name  & To destroy the contents o
  NOTE: \$ne is rounded using int() and the result must be positive. \$p must be between 0 and 1 exclusive.  & Generate an array of \$item\_cnt outcomes generated from negative binomial distribution with \$ne events and the probabilty of an event in each trial is \$p.  \\
 \hline
 \end{longtable}
+
+The \&EXT() \index{\&EXT}external function is extremely powerful, and is used to access parameters 
+and submission values.  It can be
+used within scripts and also within cell formulas in the grading spreadsheet.
+Some examples can be found by browsing in the repository to /res/msu/albertel/test/ext\_examples.html.
+The \&EXT() function can be used to obtain values for the same parameters as are retrived by some of the other (newer) helper functions  
+summarized in the table above, such as \&firstname() which is equivalent to \&EXT(`environment.firstname'),
+and \&parameter\_setting(\$name,\$partid) is equivalent to \&EXT(`resource.'.\$partid.`.'.\$name).
+In such cases the newer (specialized) functions are preferred to \&EXT() on the basis of ease of use.
+