LibreLogo Logo Turtle graphics LibreLogo LibreLogo is a simple, native, Logo-like programming environment with turtle vector graphics for teaching of computing (programming and word processing), DTP and graphic design. See http://www.numbertext.org/logo/librelogo.pdf. LibreLogo toolbar The LibreLogo toolbar (View » Toolbars » Logo) contains turtle moving, program run and stop, home and clear screen and syntax highlighting/translating icons and an input bar (command line). Turtle moving icons They are equivalents of the Logo commands “FORWARD 10”, “BACK 10”, “LEFT 15”, “RIGHT 15”. Clicking on one of the icons will also focus the turtle shape scrolling the page to its position. Program run and start Click on the icon “run” to execute the text of the Writer document as a LibreLogo program. Click on the icon “stop” to stop the program execution. Home Click on the icon “home” to reset the position and settings of the turtle. Clear screen Click on the icon “clear screen” to remove the drawing objects of the document. Command line Hit Enter in the command line to execute its content. To stop the program use the icon “stop”. Hold down the Enter to repeat the command line, for example, on the following command sequence:  FORWARD 200 LEFT 89
 To reset the command line click triple in it or press Ctrl-A to select the previous commands, and type the new commands. Syntax highlighting/Translating It expands and upper case Logo commands in the Writer document. Change the language of the document (Tools » Options » Language Settings » Languages » Western) and click on this icon to translate the Logo program to the selected language. Program editing LibreLogo drawings and programs use the same Writer document. The LibreLogo canvas is on the first page of the Writer document. You can insert a page break before the LibreLogo programs and set the zoom/font size for a comfortable two page layout for LibreLogo programming: left (first) page is the canvas, right (second) page is for the LibreLogo programs. LibreLogo programming language LibreLogo is a native, easily localisable, Logo-like programming language. It is back-compatible with the older Logo systems in the case of the simple Logo programs used in education, eg.  TO triangle :size
 REPEAT 3 [
   FORWARD :size
   LEFT 120
 ]
 END
 
 triangle 10 triangle 100 triangle 200
 Differences from the Logo programming language List members are comma separated: POSITION [0, 0] Program blocks and lists are different Program blocks need space or new line at parenthesization: REPEAT 10 [ forward 10 left 36 ] Lists need close parenthesization: POSITION [0, 0], and not POSITION [ 0, 0 ] 1-line function declarations have not supported yet (TO and END need new lines). Other features of LibreLogo The colon is optional before the variables (like in the Berkeley Logo)  TO triangle size
   REPEAT 3 [ FORWARD size LEFT 120 ]
 END
 String notation supports also orthographical and Python syntax:  PRINT "word" ; original Logo syntax
 PRINT “Arbitrary text.” ; orthography, Writer
 PRINT 'Arbitrary text.' ; Python syntax
 Python list and string handling  PRINT “text”[2] ; print “x”
 PRINT “text”[1:3] ; print “ex”
 Python-like FOR loop Python-like variable declaration:  x = 15
 PRINT x
 There are no extra query functions:  PRINT FILLCOLOR
 p = POSITION
 PRINT p
 REPEAT 10 [ POSITION ANY POSITION p ]
 Alternative parenthesization in function calls  TO star size color
 FILLCOLOR color
 REPEAT 5 [ LEFT 72 FORWARD size RIGHT 144 FORWARD size ]
 FILL
 END
 
 star 100 “red”
 star (100, “green”)
 star(100, “blue”)
 LibreLogo commands Basic syntax Case sensitivity Commands, color constants are case insensitive:  PRINT “Hello, World!”
 print “Hello, World, again!”
 Variable names are case sensitive:  a = 5
 A = 7
 PRINT a
 PRINT A
 Program lines Lines of a LibreLogo program are paragraphs in the LibreOffice Writer document. A program line can contain multiple commands:  PRINT “Hello, World!” PRINT “LibreLogo”
 Comments Lines or line parts are comments from a semicolon to the end of the line (paragraph):  ; some comments
 PRINT 5 * 5 ; some comments
 Break program lines to multiple paragraphs It’s possible to break a program line for more paragraphs using the character tilde at the end of the line:  PRINT “This is a very long ” + ~
       “warning message”
 Turtle moving FORWARD (fd)  FORWARD 10 ; move forward 10pt (1pt = 1/72 inch)
 FORWARD 10pt ; see above
 FORWARD 0.5in ; move forward 0.5 inch (1 inch = 2.54 cm)
 FORWARD 1" ; see above
 FD 1mm
 FD 1cm
 BACK (bk)  BACK 10 ; move back 10pt
 LEFT (lt)  LEFT 90 ; turn counterclockwise 90 degrees
 LEFT 90° ; see above
 LT 3h ; see above (clock position)
 LT any ; turn to a random position
 RIGHT (rt)  RIGHT 90 ; turn clockwise 90 degrees
 PENUP (pu)  PENUP ; turtle will move without drawing
 PENDOWN (pd)  PENDOWN ; turtle will move with drawing
 POSITION (pos)  POSITION [0, 0] ; turn and move to the top-left corner
 POSITION PAGESIZE ; turn and move to the bottom-right corner
 POSITION [PAGESIZE[0], 0] ; turn and move to the top-right corner
 POSITION ANY ; turn and move to a random position
 HEADING (seth)  HEADING 0 ; turn north
 HEADING 12h ; see above
 HEADING ANY ; turn to a random position
 Other turtle commands HIDETURTLE (ht)  HIDETURTLE ; hide turtle (until the showturtle command)
 SHOWTURTLE (st)  SHOWTURTLE ; show turtle
 HOME  HOME ; reset initial turtle settings and position
 CLEARSCREEN (cs)  CLEARSCREEN ; remove drawing objects of the document
 FILL and CLOSE  FILL ; close and fill the actual line shape
 CLOSE ; close the actual line shape
 Pen settings PENSIZE (ps)  PENSIZE 100 ; line width is 100 points
 PENSIZE ANY ; equivalent of PENSIZE RANDOM 10
 PENCOLOR/PENCOLOUR (pc)  PENCOLOR “red” ; set red pen color (by color name, see color constants)
 PENCOLOR [255, 255, 0] ; set yellow color (RGB list)
 PENCOLOR 0xffff00 ; set yellow color (hexa code)
 PENCOLOR 0 ; set black color (0x000000)
 PENCOLOR ANY ; random color
 PENCOLOR [5] ; set red color (by color identifier, see color constants)
 PENCOLOR “invisible” ; invisible pen color for shapes without visible outline
 PENCOLOR “~red” ; set random red color
 PENJOINT/LINEJOINT  PENJOINT “rounded” ; rounded line joint (default)
 PENJOINT “miter” ; sharp line joint
 PENJOINT “bevel” ; bevel line joint
 PENJOINT “none” ; without line joint
 PENSTYLE  PENSTYLE “solid” ; solid line (default)
 PENSTYLE “dotted” ; dotted line
 PENSTYLE “dashed” ; dashed line
 
 ; custom dot–dash pattern specified by a list with the following arguments:
 ; – number of the neighbouring dots
 ; – length of a dot
 ; – number of the neighbouring dashes
 ; – length of a dash
 ; – distance of the dots/dashes
 ; – type (optional):
 ;   0 = dots are rectangles (default)
 ;   2 = dots are squares (lengths and distances are relative to the pensize)
 
 PENSTYLE [3, 1mm, 2, 4mm, 2mm, 2] ; ...––...––...––
 Fill settings FILLCOLOR/FILLCOLOUR (fc)  FILLCOLOR “blue” ; fill with blue color, see also PENCOLOR
 FILLCOLOR “invisible” CIRCLE 10 ; unfilled circle
 FILLSTYLE  FILLSTYLE 0 ; fill without hatches (default)
 FILLSTYLE 1 ; black single hatches (horizontal)
 FILLSTYLE 2 ; black single hatches (45 degrees)
 FILLSTYLE 3 ; black single hatches (-45 degrees)
 FILLSTYLE 4 ; black single hatches (vertical)
 FILLSTYLE 5 ; red crossed hatches (45 degrees)
 FILLSTYLE 6 ; red crossed hatches (0 degrees)
 FILLSTYLE 7 ; blue crossed hatches (45 degrees)
 FILLSTYLE 8 ; blue crossed hatches (0 degrees)
 FILLSTYLE 9 ; blue triple crossed
 FILLSTYLE 10 ; black wide single hatches (45 degrees)
 
 ; custom hatches specified by a list with the following arguments:
 ; – style (1 = single, 2 = double, 3 = triple hatching)
 ; – color
 ; – distance
 ; – degree
 
 FILLSTYLE [2, “green”, 3pt, 15°] ; green crossed hatches (15 degrees)
 Drawing objects CIRCLE  CIRCLE 100 ; draw a circle shape (diameter = 100pt)
 ELLIPSE  ELLIPSE [50, 100] ; draw an ellipse with 50 and 100 diameters
 ELLIPSE [50, 100, 2h, 12h] ; draw an elliptical sector (from 2h clock position to 12h)
 ELLIPSE [50, 100, 2h, 12h, 2]  ; draw an elliptical segment
 ELLIPSE [50, 100, 2h, 12h, 3]  ; draw an elliptical arc
 SQUARE  SQUARE 100 ; draw a square shape (size = 100pt)
 RECTANGLE  RECTANGLE [50, 100] ; draw a rectange shape (50×100pt)
 RECTANGLE [50, 100, 50] ; draw a rectangle 
 POINT  POINT ; draw a point with size and color of the pen
 LABEL  LABEL “text” ; print text in the turte position
 LABEL 'text' ; see above
 LABEL "text ; see above (only for single words)
 TEXT  CIRCLE 10 TEXT “text” ; set text of the actual drawing object
 Font settings FONTCOLOR/FONTCOLOUR  FONTCOLOR “green” ; set font color
 FONTFAMILY  FONTFAMILY “Linux Libertine G” ; set font (family)
 FONTFAMILY “Linux Libertine G:smcp=1” ; set also font feature (small caps)
 FONTFAMILY “Linux Libertine G:smcp=1&onum=1” ; small caps + old figures
 FONTSIZE  FONTSIZE 12 ; set 12pt
 FONTWEIGHT  FONTWEIGHT “bold” ; set bold font
 FONTWEIGHT “normal” ; set normal weight
 FONTSTYLE  FONTSTYLE “italic” ; set italic variant
 FONTSTYLE “normal” ; set normal variant
 PICTURE (pic) PICTURE is for shape grouping; starting new line shapes; keeping the consistency of positions and line shapes at the left border. Shape grouping  ; PICTURE [ LibreLogo_commands ]
 PICTURE [ FORWARD 100 CIRCLE 100 ] ; tree-like grouped shape
 See also “Group” in LibreOffice Writer Help.  TO tree location
   PENUP POSITION location HEADING 0 PENDOWN
   PICTURE [ FORWARD 100 CIRCLE 100 ] ; tree-like grouped shape
 END
 
 PICTURE [ tree [30, 50] tree [100, 50] ] ; grouped shapes in a grouped shape
 Starting new line shapes  PICTURE ; start a new line shape
 FORWARD 10 PICTURE FORWARD 10 ; two line shapes
 Consistency at the left border Use picture to keep the consistency of positions and line shapes at the left border of Writer:  PICTURE [ CIRCLE 20 POSITION [-100, 100] CIRCLE 20 ]
 Loops REPEAT  ; REPEAT number [ commands ]
 
 REPEAT 10 [ FORWARD 10 LEFT 45 CIRCLE 10 ] ; repeat 10 times
  ; number is optional
 
 REPEAT [ POSITION ANY ] ; endless loop
 REPCOUNT Loop variable (also in the FOR and WHILE loops).  REPEAT 100 [ FORWARD REPCOUNT LEFT 90 ]
 FOR IN Loop for the list elements:  FOR i IN [1, 5, 7, 9, 11] [
   FORWARD i
   LEFT 90
 ]
 Loop for the characters of a character sequence:  FOR i IN “text” [
   LABEL i
   FORWARD 10
 ]
 WHILE  WHILE TRUE [ POSITION ANY ] ; endless loop
 WHILE REPCOUNT <= 10 [ FORWARD 50 LEFT 36 ] ; as REPEAT 10 [ ... ]
 BREAK Stop the loop.  REPEAT [ ; endless loop
   POSITION ANY
   IF REPCOUNT = 100 [ BREAK ]  ; equivalent of the REPEAT 100 [ ... ]
 ]
 CONTINUE Jump into the next iteration of the loop.  REPEAT 100 [
   POSITION ANY
   IF REPCOUNT % 2 <> 0 [ CONTINUE ]
   CIRCLE 10 ; draw circles on every 2nd positions
 ]
 Conditions IF  ; IF condition [ true block ]
 ; IF condition [ true block ] [ false block ]
 
 IF a < 10 [ PRINT “Small” ]
 IF a < 10 [ PRINT “Small” ] [ PRINT “Big” ]
 AND, OR, NOT Logical operators.  IF a < 10 AND NOT a < 5 [ PRINT “5, 6, 7, 8 or 9” ]
 Subroutines TO, END New word (or procedure).  TO triangle
   REPEAT [ FORWARD 100 RIGHT 120 ] FILL
 END
 
 REPEAT 10 [ triangle PENUP POSITION ANY PENDOWN ]
 OUTPUT Return value of the function.  TO randomletter
   OUTPUT RANDOM “qwertzuiopasdfghjklyxcvbnm”
 END
 
 PRINT randomletter + randomletter + randomletter ; print 3-letter random character sequence
 STOP Return from the procedure.  TO example number
   IF number < 0 [ STOP ]
   PRINT SQRT number ; print square root
 ]
 
 example 100
 example -1 ; without output and error
 example 25
 Default variables ANY Default random value of colors, etc.  PENCOLOR ANY ; random pen color
 TRUE Logical value.  WHILE TRUE [ POSITION ANY ] ; endless loop
 PRINT TRUE ; print true
 FALSE Logical value.  WHILE NOT FALSE [ POSITION ANY ] ; endless loop
 PRINT FALSE ; print false
 PAGESIZE  PRINT PAGESIZE ; print list of the page sizes in points, eg. [595.30, 841.89]
 PI/π  PRINT PI ; print 3.14159265359
 Input/Output PRINT  PRINT “text” ; print “text” in a dialog box
 PRINT 5 + 10 ; print 15
 INPUT  PRINT INPUT “Input value?” ; ask and print a string by a query dialog box
 PRINT FLOAT (INPUT “First number?”) + FLOAT (INPUT “Second number?”) ; simple calculator
 SLEEP  SLEEP 1000 ; wait for 1000 ms (1 sec)
 GLOBAL Set global variables used in procedures.  GLOBAL about
 about = “LibreLogo”
 
 TO example
   PRINT about
   GLOBAL about ; when we want to add a new value
   about = “new value for the global variable”
 END
 
 example
 PRINT about
 Functions RANDOM  PRINT RANDOM 100 ; random float number (0 <= x < 100)
 PRINT RANDOM “text” ; random letter of the “text”
 PRINT RANDOM [1, 2] ; random list element (1 or 2)
 INT  PRINT INT 3.8 ; print 3 (integer part of 3.8)
 PRINT INT RANDOM 100 ; random integer number (0 <= x < 100)
 PRINT INT “7” ; convert the string parameter to integer
 FLOAT  ; convert the string parameter to float number
 PRINT 2 * FLOAT “5.5” ; print 11.0
 STR  ; convert the number parameter to string
 PRINT “Result: ” + STR 5 ; print “Result: 5”
 PRINT 10 * STR 5 ; print 5555555555
 SQRT  PRINT SQRT 100 ; print 10, square root of 100
 SIN  PRINT SIN 90 * PI/180 ; print 1.0 (sinus of 90° in radians)
 COS  PRINT COS 0 * PI/180 ; print 1.0 (sinus of 0° in radians)
 ROUND  PRINT ROUND 3.8 ; print 4 (rounding 3.8)
 PRINT ROUND RANDOM 100 ; random integer number (0 <= x <= 100)
 ABS  PRINT ABS -10 ; print 10, absolute value of -10
 COUNT  PRINT COUNT “text” ; print 4, character count of “text”
 PRINT COUNT [1, 2, 3] ; print 3, size of the list
 SET  ; Convert list to Python set
 PRINT SET [4, 5, 6, 6] ; print {4, 5, 6}
 PRINT SET [4, 5, 6, 6] | SET [4, 1, 9] ; print {1, 4, 5, 6, 9}, union
 PRINT SET [4, 5, 6, 6] & SET [4, 1, 9] ; print {4}, intersection
 PRINT SET ([4, 5, 6, 6]) - SET [4, 1, 9] ; print {5, 6}, difference
 PRINT SET [4, 5, 6, 6] ^ SET [4, 1, 9] ; print {1, 5, 6, 9}, symmetric difference  
 RANGE  ; Python-like list generation
 PRINT RANGE 10 ; print [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
 PRINT RANGE 3 10 ; print [3, 4, 5, 6, 7, 8, 9]
 PRINT RANGE 3 10 3 ; print [3, 6, 9]
 
 FOR i in RANGE 10 50 10 [ ; loop for [10, 20, 30, 40]
   FORWARD i
   LEFT 90
 ]
 LIST  ; remove the repeating elements of a list using set and list conversion
 PRINT LIST (SET [1, 3, 5, 5, 2, 1]) ; print [1, 3, 5, 2]
 TUPLE Conversion to Python tuple (non-modifiable list)  PRINT TUPLE [4, 5]
 SORTED It returns with a sorted list.  PRINT SORTED [5, 1, 3, 4] ; print [1, 3, 4, 5]
 SUB Substitue character sequences using regex (regular expression) patterns.  PRINT SUB (“t”, “T”, “text”) ; print “Text”, replacing “t” with “T”
 PRINT SUB (“(.)”, “\\1\\1”, “text”) ; print “tteexxtt”, doubling every characters
 SEARCH Search character sequences patterns using regex patterns.  IF SEARCH (“\w”, word) [ PRINT “Letter in the word.” ]
 FINDALL Find all character sequences in the input string matching the given regex pattern.  PRINT FINDALL(“\w+”, “Dogs, cats.”) ; print [“Dogs”, “cats”], the list of the words.
 MIN  PRINT MIN [1, 2, 3] ; print 1, the lowest element of the list
 MAX  PRINT MAX [1, 2, 3] ; print 3, the greatest element of the list
 Color constants  PENCOLOR “SILVER” ; set by name
 PENCOLOR [1] ; set by identifiers
 PENCOLOR “~SILVER” ; random silver color
 
 Identifier Name 0 BLACK 1 SILVER 2 GRAY/GREY 3 WHITE 4 MAROON 5 RED 6 PURPLE 7 FUCHSIA/MAGENTA 8 GREEN 9 LIME 10 OLIVE 11 YELLOW 12 NAVY 13 BLUE 14 TEAL 15 AQUA 16 PINK 17 TOMATO 18 ORANGE 19 GOLD 20 VIOLET 21 SKYBLUE 22 CHOCOLATE 23 BROWN 24 INVISIBLE