Elmer uses MATC to evaluate mathematical expressions in the Solver Input Files. Also ElmerPost includes MATC.
MATC was written by Juha Ruokolainen.
You can find the official manual at http://www.nic.funet.fi/pub/sci/physics/elmer/doc/MATCManual.pdf
Embedding in sif files
There are two options for embedding MATC in Solver Input Files. Variables can be defined as
gravity = Real $ 0 0 -1 *9.81 ! evaluation at program start
Which would be evaluated once at program start. or by
gravity = Real MATC 0 0 -1 * 9.81 ! evaluation at every use
which is evaluated every time the gravity variable is used.
Calling MATC from the command line
MATC can be called from the command line by calling $ELMER_HOME/bin/matc. Under Unix/Linux this should be part of your $PATH and calling matc should suffice.
To quit using command line MATC type quit .
The mathematical operations are evaluated from high to low precedence and within each level from left to right (everything as usual).
The most important operators ordered from high to low precedence:
() (parentheses) ' ' (SPACE as a separator for vector components) ^ (power) */ +-
A full list can be found in the MATC Manual.
Scalars and Vectors
Vectors in MATC are written by separating their entries with spaces. Since the space forming vectors has a higher precedence than the algebraic operations
min(3*4 2) = min(12 6) = 6
min((3*4) 2) = min(12 2) = 2
this can lead to strange behavior of boundary conditions if the parentheses are forgotten.