ConstructClause

Construct statements offer the possibility to automatically construct quantities based on previously read in boundary elements for GeometryManipulations like offset{, scale{, rotate{. The construct statements are evaluated sequentially in the startup phase together with the reading of the geometry files and this evaluation is depending on the order. A typical order can be:

• read in a subset of geometry files
• establish a sequence of ConstructClause items for those geometries
• apply the results of the ConstructClause items in a subsequent reading of other geometry files

A construct statement may look as follows: The possible CONSTRUCT-keywords can be found at the very bottom in the List of members. Note: Whenever there is a construction based on an alias list "alias1", "alias2", ..., also wildcards can be used. For example, "alias*" matches "alias1", "alias2", ..., see AliasForGeometryItems.

Construct Environments

If the construct result is used in several places of the USER_common_variables, a construct environment is preferred: The result can be referenced by the name given on the left hand side in the same way as an ALIAS, see also Variables. Notes:

• begin_boundary_elements{ and begin_construct{ blocks are read sequentially. All geometry parts used in a construct statement must be defined beforehand.
• begin_construct{ environments are only evaluated at regular startup of a simulation, not during RESTART. Hence, for construct results that are supposed to be re-evaluated during restart, use
  begin_construct_atRestart{} ... end_construct_atRestart
  These are not read during regular startup. Consequently, to update the values correctly also during restart, begin_construct_atRestart{ and begin_construct{ have to used both.

(Experimental) begin_construct_always{

Another way to read in construct statements is using the begin_construct_always{ environment. This allows to define construct variables for regular startup and restart runs in the same environment. MESHFREE internally identifies if its a restarted run and automatically overwrites the updated construct variables which might be based on the updated boundary. Warning: Using begin_construct_always{ and begin_construct{ in the same setup or, respectively, begin_construct_always{ and begin_construct_atRestart{ is not recommended. There is a workaround to support this if CONTROL_ConstructClauses > 0. If CONTROL_ConstructClauses = 0 (default), this will result in an error termination.

Examples

Example 1: Using construct to manipulate the read-in of other geometry parts Example 2: Any RightHandSideExpression can be used to save the result of a calculation during the initialization phase into an ALIAS, for example to create new boundary elements from scratch after reading in other geometry. Example 3: Using a vectorial ALIAS on the right hand side of construct statements Warning: When using version 2, make sure to stick to the correct syntax, e.g. putting "&GeoGroup&" instead of &GeoGroup& on the right hand side will lead to an incorrect result. Example 4: Using a vectorial ALIAS on the left hand side of construct statements If parenthesis are found on the left hand side of a construct statement, MESHFREE will interpret this as an indexing into a vectorial ALIAS. The right hand side result will be placed at the specified location within the comma-separated vectorial ALIAS string. In the above example, a vectorial ALIAS "vecAlias" with (at least) the first five components (1,4,9,16,25) will be created and, susequently, the third component will be overwritten to give (1,4,25,16,25). The example also shows how certain functions can be evaluated on the list of values stored in "vecAlias". Here, we determine the minimum and maximum values, which is possible since the comma-seperated list of values in "vecAlias" is simply put into the min() or max() function as a string when the alias reference &vecAlias& is resolved. Warning: Do not mix double definitions of aliases outside of construct statements with the above indexing!