LibreLogo is a simple, localised, 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.

The LibreLogo toolbar (View - Toolbars - Logo) contains turtle moving, program start, stop, home, clear screen, program editor/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.

Start Logo program

Click on the icon “Start Logo program” to execute the text (or only the selected) text of the Writer document as a LibreLogo program. In an empty document an example program will be inserted and executed.

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.

Program editor/Syntax highlighting/Translating

The “magic wand” icon sets 2-page layout for program editing, expands and converts to upper-case the abbreviated, lower-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.

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 triple-click it or press Ctrl +A to select the previous commands, and type the new commands.

Graphical user interface of basic turtle settings

Turtle shape of LibreLogo is a normal fixed size drawing object. You can position and rotate it using the mouse and the Rotate icon of the Drawing Object Properties toolbar. Modify Line Width, Line Colour and Area Colour settings of the turtle shape to set PENSIZE, PENCOLOUR and FILLCOLOUR attributes of LibreLogo.

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 page zoom using the “magic wand” icon of the Logo toolbar, also change the font size for a comfortable 2-page layout for LibreLogo programming: left (first) page is the canvas, right (second) page is the LibreLogo program editor.

LibreLogo programming language

LibreLogo is an easily localisable, Logo-like programming language, localised in several languages by Office native language communities. 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 parenthesisation: REPEAT 10 [ FORWARD 10 LEFT 36 ]
- Lists need close parenthesisation: POSITION [0, 0], and not POSITION [ 0, 0 ]
1-line function declarations are not supported (TO and END need new lines).

Other features of LibreLogo

The colon is optional before the variable names.

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 FILLCOLOUR
p = POSITION
PRINT p
REPEAT 10 [ POSITION ANY POSITION p ]

Alternative parenthesisation in function calls

TO star size colour
FILLCOLOUR colour
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, colour 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 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 [0, 0] ; turn to the top-left corner
HEADING ANY ; turn to a random direction

Other turtle commands

HIDETURTLE (ht)

HIDETURTLE ; hide turtle (until the showturtle command)

SHOWTURTLE (st)

SHOWTURTLE ; show turtle

HOME

HOME ; reset initial turtle position

CLEARSCREEN (cs)

CLEARSCREEN ; remove drawing objects of the document

FILL and CLOSE

FILL ; close and fill the actual line shape or points
CLOSE ; close the actual line shape or join the actual points

Example: filling a regular triangle:

FORWARD 50 LEFT 120 FORWARD 50 FILL

Example: drawing a regular triangle:

FORWARD 50 LEFT 120 FORWARD 50 CLOSE

Pen settings

PENSIZE (ps)

PENSIZE 100 ; line width is 100 points
PENSIZE ANY ; equivalent of PENSIZE RANDOM 10

PENCOLOR/PENCOLOUR (pc)

PENCOLOUR “red” ; set red pen colour (by colour name, see colour constants)
PENCOLOUR [255, 255, 0] ; set yellow colour (RGB list)
PENCOLOUR 0xffff00 ; set yellow colour (hexa code)
PENCOLOUR 0 ; set black colour (0x000000)
PENCOLOUR ANY ; random colour
PENCOLOUR [5] ; set red colour (by colour identifier, see colour constants)
PENCOLOUR “invisible” ; invisible pen colour for shapes without visible outline
PENCOLOUR “~red” ; set random red colour

PENTRANSPARENCY

PENTRANSPARENCY 80 ; set the transparency of the actual pen colour to 80%

PENCAP/LINECAP

PENCAP “none” ; without extra line end (default)
PENCAP “round” ; rounded line end
PENCAP “square” ; square line end

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)

FILLCOLOUR “blue” ; fill with blue colour, see also PENCOLOUR
FILLCOLOUR “invisible” CIRCLE 10 ; unfilled circle
FILLCOLOUR [“blue”, “red”] ; gradient between red and blue
FILLCOLOUR [[255, 255, 255], [255, 128, 0]] ; between white and orange
FILLCOLOUR [“blue”, “red”, 1, 0, 0] ; set axial gradient (with the required rotation and border settings), possible values: 0-5 = linear, axial, radial, elliptical, square and rectangle gradients
FILLCOLOUR [“red”, “blue”, 0, 90, 20] ; linear with 20% border, rotated with 90 degrees from the actual heading of the turtle
FILLCOLOUR [“red”, 'blue”, 0, 90, 20, 0, 0, 200, 50] ; from 200% to 50% intensity
FILLCOLOUR [ANY, ANY, 2, 0, 0, 50, 50] ; radial gradient with random colours and 50-50% horizontal and vertical positions of the centre

FILLTRANSPARENCY

FILLTRANSPARENCY 80 ; set the transparency of the actual fill colour to 80%
FILLTRANSPARENCY [80] ; set linear transparency gradient from 80% to 0%
FILLTRANSPARENCY [80, 20] ; set linear transparency gradient from 80% to 20%
FILLTRANSPARENCY [80, 20, 1, 90] ; set axial transparency gradient rotated with 90 degrees from the actual heading of the turtle
FILLTRANSPARENCY [80, 20, 2, 0, 20, 50, 50] ; set radial transparency gradient from outer 80% to inner 20% transparency with 20% border and with 50-50% horizontal and vertical positions of the centre

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)
; – colour
; – 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 rectangle shape (50×100pt)
RECTANGLE [50, 100, 10] ; draw a rectangle with rounded corners

POINT

POINT ; draw a point with size and colour of the pen

CLOSE can join the last points, FILL can fill the shape defined by points. For example, it’s easy to draw a “flat” star starting from its centre:

PENUP
REPEAT 5 [
FORWARD 80
POINT
BACK 80
RIGHT 36
FORWARD 50
POINT
BACK 50
RIGHT 120
] FILL

LABEL

LABEL “text” ; print text in the turtle 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

FONTCOLOUR “green” ; set font colour

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

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;
saving SVG images and SVG/SMIL animations;
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 Office Writer Help.

TO tree location
PENUP POSITION location HEADING 0 PENDOWN
PICTURE [ FORWARD 100 CIRCLE 100 ] ; tree-like grouped shape
END

PICTURE [ tree [230, 400] tree [300, 400] ] ; grouped shapes in a grouped shape

Starting new line shapes

PICTURE ; start a new line shape
FORWARD 10 PICTURE FORWARD 10 ; two line shapes

Saving SVG images

PICTURE “example.svg” [ CIRCLE 5 ] ; save the picture as an SVG image file in the user folder
PICTURE “Desktop/example.svg” [ FORWARD 100 CIRCLE 5 ] ; as above, with a relative path
PICTURE “/home/user/example.svg” [ CIRCLE 5 ] ; absolute path for Unix/Linux
PICTURE “C:\example.svg” [ CIRCLE 5 ] ; absolute path for Windows

Saving SVG/SMIL animations (drawings with SLEEP commands)

PICTURE “animation.svg” [ CIRCLE 5 SLEEP 1000 CIRCLE 99 ] ; save as an SVG/SMIL animation (see also SLEEP)
PICTURE “animation2.svg” [ CIRCLE 5 SLEEP 1000 CIRCLE 99 SLEEP 2000 ] ; as above, but using SLEEP after the last object will result looping: after 2 seconds the SVG animation restarts in SMIL-conformant browsers

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 “0, 1, 2, 3, 4, 6, 7, 8 or 9” ]
IF a < 10 AND a != 5 [ PRINT “0, 1, 2, 3, 4, 6, 7, 8 or 9” ] ; as above

Subroutines

TO, END

New word (or procedure).

TO triangle
REPEAT 2 [ 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 colours, etc.

PENCOLOUR ANY ; random pen colour

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, e.g. [595.30, 841.89]

PI/π

PRINT PI ; print 3.14159265359

Input/Output

PRINT

PRINT “text” ; print “text” in a dialogue box
PRINT 5 + 10 ; print 15

INPUT

PRINT INPUT “Input value?” ; ask and print a string by a query dialogue 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 (cosine of 0° in radians)

LOG10

PRINT LOG10 100 ; print 2.0 (common logarithm of 100)

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 LIST RANGE 10 ; print [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
PRINT LIST RANGE 3 10 ; print [3, 4, 5, 6, 7, 8, 9]
PRINT LIST 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

Substitute 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

Colour constants

PENCOLOUR “SILVER” ; set by name
PENCOLOUR [1] ; set by identifiers
PENCOLOUR “~SILVER” ; random silver colour

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

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