C.a.R. > Documentation > File Format

File Format of C.a.R.

Introduction

C.a.R. uses the standard XML to store constructions. This format can be easily read by humans, and even edited without the C.a.R. program.

If you use compression to store files, you will not be able to read these files. Compression is done by standard compression methods in Java. The files can be decompressed with gzip.

XML files can be edited by many programs. To save the files, you can use either UTF-8 encoding or ISO-8869-1, which is the usual Windows encoding, and the default, if the encoding is not explicitly mentioned. The Microsoft Internet Explorer can display XML too, if they have the extension XML.

The structure

The general structure may be seen from the following example.

<?xml version="1.0" encoding="utf-8"?>
<CaR>
<Construction>
<Window x="0.0" y="0.0" w="8.0"/>
<Comment>
<P>Constructs the perpendicular bisector for the segment
through the two points.</P>
</Comment>
<Objects>
<Point name="P1" x="-3.9940740740740743" y="-1.1259259259259267">Point at -3.9940740740740743, -1.1259259259259267</Point>
<Point name="P2" x="1.53" y="1.17">Point at 1.53, 1.17</Point>
<Circle name="c1" through="P2" midpoint="P1" acute="true">Circle around P1 through P2</Circle>
<Circle name="c2" through="P1" midpoint="P2" acute="true">Circle around P2 through P1</Circle>
<Intersection name="I2" first="c1" second="c2" which="second">Intersection between c1 and c2</Intersection>
<Intersection name="I3" first="c1" second="c2" which="first">Intersection between c1 and c2</Intersection>
<Line name="l1" from="I2" to="I3">Line through I2 and I3</Line>
</Objects>
</Construction>
</CaR>

The file consists of tags like

<Objects>
...
</Objects>

Every tag has a start and an end, and a content in between. If there is no content, the following syntax may be used.

<Window .../>

Moreover, the start may have parameters.

<Point name="Punkt 1" x="-0.4036697247706422" y="-0.05504587155963303">Punkt in -0.4036697247706422, -0.05504587155963303</Point>

There are other special tags, which describe the XML file itself. The first line must be

<?xml version="1.0" encoding="utf-8"?>

<?xml version="1.0" encoding="iso-8859-1"?>

The version and the encoding can be omitted, if the file is for C.a.R.

This is a first self made example.

<?xml?>
<CaR>
<Construction>
<Window x=0 y=0 w=5/>
<Comment>
<P>Construction of a perpendicular on the middle of a line!</P>
</Comment>
<Objects>
<Point name=P x=-1 y=0/>
<Point name=Q x=1 y=0/>
<Circle name=k1 midpoint=P through=Q hidden/>
<Circle name=k2 midpoint=Q through=P hidden/>
<Intersection name=A first=k1 second=k2 other=B hidden/>
<OtherIntersection name=B hidden/>
<Line name=g from=A to=B/>
</Objects>
</Construction>
</CaR>

The Window tag describes the center of the display and its width.

This file cannot be read by Internet Explorer, since it expects the parameters in quotes "".

Frame tags

CaR	Must embrace the file.
Construction	Embraces a construction. The job parameter will identify an assignment. The value of this parameter does not matter, but should be "true". For each job, there must be the parameters last and target which define the last object to be displayed and the target of the assignment.
Window	Sets the viewport. Parameters are x, y, and w, the center and the screen width.
Comment	Contains the comment. It consists of either a sequence of paragraphs (each like <P>...</P>), or a single paragraph.
Assignment	Comment to display the assignment.
Objects	The construction. See below.
Macro	Similar to Objects. See below.

Construction Elements

Point	x=0 y=0	A point in (x,y).
Line	from=A to=B	The line AB.
Segment	from=A to=B	The segment AB.
Ray	from=A to=B	The ray from A through B.
Circle	midpoint=M through=P	The circle around M through P. If throuhg is missing you must provide fixed.
Circle3	midpoint=M from=A to=B	The circle around M with radius AB.
Intersection	first=X second=Y other=B	The intersection of X and Y. B is the name of the other intersection point.
OtherIntersection		Describes the properties of the other intersection points. May be missing.
Parallel	point=A line=g	The parallel to g through A.
Plumb	point=A line=g	The perpendicular to g through A.
Angle	first=A root=B second=C	The angle ABC.

These objects can have further parameters.

name	The name of the object.
color	One of the numbers 0,1,2,3. The number 0 means black.
type	One of the values thick, thin or normal.
showname	If this is defined, the name will be displayed.
showvalue	Displays the value.
hidden	Hides the object.
fixed	Fixes the object size to the value. Points use the value true, since the coordinates are fixed in this case
partial	Displays circles and lines partially.
away	Only for intersections. See the description of intersections in the documentation

C.a.R. > Documentation > File Format