====== Set Pipeline Parameter From Expression ======
This command can be used to set the value of a specified parameter by defining it with an expression. This allows the value of a parameter to be set to anything from an explicit value to an expression containing other signals. 

====Pipeline Command====
The command can be found in the Pipeline Workshop within the Pipeline Control folder as so:
<code>
Set_Pipeline_Parameter_From_Expression
/PARAMETER_NAME=
/EXPRESSION=
! /AS_INTEGER=TRUE
;
</code>

====Command Parameters====
The following table shows the command parameters that can be used to define the command and their descriptions:
|**Parameter**   |**Description**|
|**Parameter Name**|The name of the Pipeline Parameter. The parameter is referred to by other commands using two colons (::) in front of the parameter name|
|**Expression**|The expression used to define the parameter value|
|**As Integer**|True or False: Express the resulting parameter value as an integer|

For more information on how expressions can be used and defined see [[visual3d:documentation:pipeline:expressions:expressions_overview|Expressions Overview]].

====Syntax Notes====

<code>
Set_Pipeline_Parameter_From_Expression
/PARAMETER_NAME=t_Mass
/EXPRESSION=METRIC::PROCESSED::HEIGHT * 4.6
/AS_INTEGER=TRUE
;
</code>
The pipeline parameter contains the value of the expression.

Getting the syntax correct can be challenging because there can be a conflict between the & as a concatenation parameter in a pipeline parameter and the & as a boolean "and" operator.

For many pipeline commands Visual3D recognizes the conflict and handles the situations in a context specific way.

Visual3D cannot make that distinction and "bad" things happen.

Consider the following which uses string comparisons and a pipeline parameter in the expression:

<code>
Set_Pipeline_Parameter_From_Expression
/PARAMETER_NAME= MVAL
/EXPRESSION=(&::TAG_NAMES& == Utility) * 4.6
/AS_INTEGER=FALSE
;
</code>

The goal was to set MVAL to 4.6 when the pipeline parameter TAG_NAMES was equal to the string "Utility";

One solution is to separate the pipeline parameter from the expression.

<code>
Set_Pipeline_Parameter
/PARAMETER_NAME=TEMP
/PARAMETER_VALUE=(&::TAG_NAMES& == Utility)*4.6
;
</code>
\\

<code>
Set_Pipeline_Parameter_From_Expression
/PARAMETER_NAME=t_Mass
/EXPRESSION=::TEMP
/AS_INTEGER=FALSE
;
</code>

\\
Another solution, which is even trickier in terms of syntax is:

<code>
Set_Pipeline_Parameter_From_Expression
/PARAMETER_NAME=SCOTT
/EXPRESSION=("&::TAG_NAMES&"==" Utility")
! /AS_INTEGER=TRUE
;
</code>

This forces Visual3D to recognize the strings as strings and the & is treated correctly.

\\


====Example: Get global metrics ====
Global metrics can be set to a pipeline parameter by setting "GLOBAL" in front of the metric name. More information about expressions can be found [[Visual3D:Documentation:Pipeline:Expressions:Expressions_Overview|here]].

<code>
Set_Pipeline_Parameter_From_Expression
/PARAMETER_NAME=KATIE
/EXPRESSION=GLOBAL::METRIC::PROCESSED::MASS
/AS_INTEGER=FALSE
;
</code>