I am now digging into Pillar. My goal is to be able to insert Roassal script and having it executed.

Scripts provided within [[[ ]]] may be evaluated using the variable ‘eval=true’. Here is an example:

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PRHTMLWriter defaultConfigurations anyOne
    inputString: '100 factorial =
[[[eval=true
stream nextPutAll: 100 factorial asString
]]]';
    outputFile: 'myFirstPillarExport.html' asFileReference;
    export

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‘stream’ is a hardcoded variable name which represents the stream on which you have to write your result. What you write in stream is pillar-friendly. This means you can write something like: 

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PRHTMLWriter defaultConfigurations anyOne
    inputString: '100 factorial =
[[[eval=true
stream nextPutAll: ''""'', 100 factorial asString, ''""''
]]]';
    outputFile: 'myFirstPillarExport.html' asFileReference;
    export

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I have tried to insert some Roassal visualization, and it works pretty well.

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PRHTMLWriter defaultConfigurations anyOne
    inputString: '
!!Example of a factorial
50 factorial =
[[[eval=true
stream nextPutAll: ''""'', 100 factorial asString, ''""''.
]]]

!!Some Roassal visualizations
Here is a small Mondrian example
[[[eval=true

b := RTMondrian new.
b nodes: (1 to: 100).
b layout grid.
b build.

aView := b view.
RTHTML5Exporter new insert: aView named: ''Roassal test'' inPillarStream: stream
]]]

Another example with Grapher this time:
[[[eval=true
b := RTGrapher new.
b extent: 300 @ 200.

ds := RTStackedDataSet new.
ds interaction popupText.
ds barShape width: 10.
ds points: #(4 5 1 -2 5 6).
b add: ds.
"b axisX noLabel; noTick.
"

b build.

RTHTML5Exporter new insert: b view named: ''A Graph'' inPillarStream: stream
]]]

';
    outputFile: 'myFirstPillarExport.html' asFileReference;
    export

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Pillar is very well done! Congrats to the authors!

Cheers,

Alexandre