add documenation on expression parser to UserGuide

git-svn-id: http://svn.cactuscode.org/flesh/trunk@4798 17b73243-c579-4c4c-a9d2-2d5706c11dac

1 files changed, 52 insertions, 0 deletions

diff --git a/doc/UsersGuide/Notes.tex b/doc/UsersGuide/Notes.tex
index b2393291..ff0a6f42 100644
--- a/doc/UsersGuide/Notes.tex
+++ b/doc/UsersGuide/Notes.tex
@@ -1313,6 +1313,58 @@ consists of one or more parameter names, followed by
 an `\texttt{=}', followed by the value(s) for this (these) parameter(s).
 Note that all string parameters are case insensitive.
 
+Parameters statements of numeric or boolean type can use arithmetic
+expressions in place of explicit values. The usual arithmetic operations
+as well as C-like transcendental functions and relational operations are
+supported. Integer division is handled as in C, and any non-null value is
+interpreted as logical true, which the relational operators return as unity.
+Table~\ref{tab:expression_functions} lists the supported functions.
+Expressions can refer to already set parameters by using the fully qualified
+name \texttt{thorn::parameter} as described below.
+\begin{table}
+    \begin{tabular}{|ll@{\hspace{.5cm}}|ll|}
+        \hline
+        \multicolumn{2}{|c|}{Relational operators} & \multicolumn{2}{c|}{Mathematical functions} \\
+        \hline
+        \verb|=| & tests for equality		 & \verb|!| & logical not\\
+        \hline
+        \verb|<| & tests for less than		 & \verb|acos| & inverse cosine\\
+        \hline
+        \verb|>| & tests for greater than	 & \verb|asin| & inverse sine\\
+        \hline
+        \verb|<=| & tests for less or equal	 & \verb|atan| & inverse tangent \\
+        \hline
+        \verb|>=| & tests for greater or equal	 & \verb|ceil| & round up to nearest integer \\
+        \hline
+        \verb|&&| & logical and		         & \verb|cos| & cosine \\
+        \hline
+        \verb%||% & logical or		         & \verb|cosh| & hyperbolic cosine \\
+        \hline
+        \multicolumn{2}{|c|}{Unary operators}	 & \verb|exp| & exponentiation $e^x$\\
+        \hline
+        \verb|-| & negate sign		         & \verb|fabs| & absolute value $|x|$\\
+        \hline
+        \verb|+| & no-op                         & \verb|floor| & round down to nearest integer \\
+        \hline
+        \multicolumn{2}{|c|}{Binary operators}	 & \verb|log| & natural logarithm \\
+        \hline
+        \verb|+| & addition		         & \verb|log10| & base-10 logarithm \\
+        \hline
+        \verb|-| & subtraction		         & \verb|sin| & sine \\
+        \hline
+        \verb|/| & C-like division		 & \verb|sinh| & hyperbolic sine \\
+        \hline
+        \verb|*| & multiplication		 & \verb|sqrt| & square root \\
+        \hline
+        \verb|^| & exponentiation $x^y$		 & \verb|tan| & tangent \\
+        \hline
+                 &                               & \verb|tanh| & hyperbolic tangent \\
+        \hline
+    \end{tabular}
+    \caption{Supported functions inside of expressions, in increasing order of
+    precedence.}
+\end{table}
+
 The first parameter statement in any parameter file should set \texttt{ActiveThorns},
 which is a special parameter that tells the
 program which \textit{thorns} are to be activated.  Only parameters from active