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/**
* SVG turtle graphics.
*
* Warranty & Liability
* To the extent permitted by applicable law and unless explicitly
* otherwise agreed upon, XLOG Technologies AG makes no warranties
* regarding the provided information. XLOG Technologies AG assumes
* no liability that any problems might be solved with the information
* provided by XLOG Technologies AG.
*
* Rights & License
* All industrial property rights regarding the information - copyright
* and patent rights in particular - are the sole property of XLOG
* Technologies AG. If the company was not the originator of some
* excerpts, XLOG Technologies AG has at least obtained the right to
* reproduce, change and translate the information.
*
* Reproduction is restricted to the whole unaltered document. Reproduction
* of the information is only allowed for non-commercial uses. Selling,
* giving away or letting of the execution of the library is prohibited.
* The library can be distributed as part of your applications and libraries
* for execution provided this comment remains unchanged.
*
* Restrictions
* Only to be distributed with programs that add significant and primary
* functionality to the library. Not to be distributed with additional
* software intended to replace any components of the library.
*
* Trademarks
* Jekejeke is a registered trademark of XLOG Technologies AG.
*/
:- ensure_loaded(library(misc/markup)).
:- ensure_loaded(library(misc/vector)).
/*********************************************************/
/* Turtle Commands */
/*********************************************************/
% current_angle(-Float)
:- dynamic current_angle/1.
% current_position(-Float, -Float)
:- dynamic current_position/2.
% begin
begin :-
retractall(current_angle(_)),
assertz(current_angle(0)),
retractall(current_position(_,_)),
assertz(current_position(50,350)),
svg_begin([]).
/**
* turn(D):
* The predicate succeeds. As a side effect the turtle
* orientation is turned by D radians.
*/
% turn(+Float)
turn(D) :-
retract(current_angle(A)),
A2 is A+D,
assertz(current_angle(A2)).
/**
* move(D):
* The predicate succeeds. As a side effect the turtle
* moves by D steps, not leaving any trace.
*/
% move(+Float)
move(D) :-
retract(current_position(X1,Y1)),
current_angle(A),
X2 is X1+D*cos(A),
Y2 is Y1+D*sin(A),
assertz(current_position(X2,Y2)).
/**
* line(D):
* The predicate succeeds. As a side effect the turtle
* moves by D steps, drawing a line.
*/
% line(+Float)
line(D) :-
retract(current_position(X1,Y1)),
current_angle(A),
X2 is X1+D*cos(A),
Y2 is Y1+D*sin(A),
assertz(current_position(X2,Y2)),
svg_line(X1,Y1,X2,Y2,'pen').
% end
end :-
svg_end.