This is the README for QLogo and Psychi.

Copyright

Copyright (C) 2017-2026 Jason Sikes

Redistribution and use in source and binary forms, with or without modification, are permitted under the conditions specified in the license found in the LICENSE file in the project root.

About

QLogo

QLogo is a compiler for the UCBLogo language written in C++ using Qt and LLVM. It mimics the UCBLogo interpreter developed by Brian Harvey, et al. at U.C. Berkeley.

You can find more information about the UCBLogo language using the UCBLogo Manual here:

http://people.eecs.berkeley.edu/~bh/usermanual

The QLogo compiler is incomplete. For an actual working UCBLogo interpreter see:

https://github.com/jrincayc/ucblogo-code

Psychi

Psychi is the graphical terminal window for QLogo. It provides a command line, a text editor, and a turtle graphics window.

To build

At this time I am developing and testing QLogo on the following systems:

• Linux (Fedora 43 using Qt 6.10 and LLVM 21), and
• macOS (Tahoe on Silicon, using LLVM 21 and Qt 6.10 provided by MacPorts).

I am no longer testing on MS Windows as I no longer have a Windows machine.

To build in Linux

Make sure you have the required components installed. This would involve using your package manager.

To the best of my memory, you will need the following packages:

• CMake
• Make
• C++ development packages
• Qt6 development packages, at least 6.5. Qt6 is big; your distribution may make some of the components “optional”. Make sure you have:
  • The Qt6 SQLite development package
  • The Qt6 SVG development package.
• LLVM development packages, at least version 21.

After you have downloaded the QLogo source code, “cd” into the source directory and issue the following commands.

cmake -S . -B build
cd build
make

If everything is successful, you should find the built components in the build directory. It’s not a good idea to move the items to another location; I don’t even know if the “install” script works correctly.

The QLogo compiler and command-line program will be found at:

QLogo/build/qlogo/qlogo

and the graphical user interface with the turtle can be found at:

QLogo/build/Psychi/Psychi

More about QLogo

QLogo aims to imitate, as much as I find reasonable, the UCBLogo programming language and user interface.

Development of QLogo is still ongoing. Following is my chart of commands. The commands that are not yet completed are marked “TODO”.

CONTROL STRUCTURES	GRAPHICS	ARITHMETIC	COMMUNICATION	DATA STRUCTURE PRIMITIVES	WORKSPACE MANAGEMENT
	COMPLETE	COMPLETE		COMPLETE
RUN	FORWARD	SUM	PRINT	WORD	TO
TODO TIME	FD	DIFFERENCE	PR	LIST	.MACRO
TODO MARK	BACK	MINUS	TYPE	SENTENCE	TODO DEFINE
RUNRESULT	BK	-	SHOW	SE	TODO .DEFMACRO
BYE	LEFT	PRODUCT	TODO READLIST	FPUT	TODO TEXT
REPEAT	LT	QUOTIENT	TODO RL	LPUT	TODO FULLTEXT
FOREVER	RIGHT	REMAINDER	TODO READWORD	ARRAY	TODO COPYDEF
REPCOUNT	RT	MODULO	TODO RW	LISTTOARRAY	MAKE
IF	SETPOS	INT	TODO READRAWLINE	ARRAYTOLIST	LOCAL
IFELSE	SETXY	ROUND	TODO READCHAR	FIRST	TODO THING
TEST	SETX	SQRT	TODO READCHARS	LIBRARY FIRSTS	TODO GLOBAL
IFTRUE	SETY	POWER	TODO RCS	LAST	TODO PPROP
IFT	SETHEADING	EXP	TODO FILEDIALOG	BUTFIRST	TODO GPROP
IFFALSE	SETH	LOG10	TODO COPYRIGHT	BF	TODO REMPROP
IFF	HOME	LN	TODO SHELL	LIBRARY BUTFIRSTS	TODO PLIST
STOP	ARC	SIN	TODO SETPREFIX	LIBRARY BFS	TODO PROCEDUREP
OUTPUT	POS	RADSIN	TODO PREFIX	BUTLAST	TODO PROCEDURE?
OP	HEADING	COS	TODO OPENREAD	BL	TODO MACROP
.MAYBEOUTPUT	TOWARDS	RADCOS	TODO OPENWRITE	ITEM	TODO MACRO?
CATCH	SCRUNCH	ARCTAN	TODO OPENAPPEND	SETITEM	TODO PRIMITIVEP
THROW	SHOWTURTLE	RADARCTAN	TODO OPENUPDATE	.SETFIRST	TODO PRIMITIVE?
ERROR	ST	LESSP	TODO CLOSE	.SETBF	TODO DEFINEDP
PAUSE	HIDETURTLE	LESS?	TODO ALLOPEN	.SETITEM	TODO DEFINED?
CONTINUE	HT	GREATERP	TODO CLOSEALL	WORDP	TODO NAMEP
CO	CLEAN	GREATER?	TODO ERASEFILE	WORD?	TODO NAME?
TAG	CLEARSCREEN	LESSEQUALP	TODO ERF	LISTP	TODO PLISTP
GOTO	CS	LESSEQUAL?	TODO DRIBBLE	LIST?	TODO PLIST?
TODO APPLY	WRAP	GREATEREQUALP	TODO NODRIBBLE	ARRAYP	TODO CONTENTS
TODO ?	WINDOW	GREATEREQUAL?	TODO SETREAD	ARRAY?	TODO BURIED
	FENCE	RANDOM	TODO SETWRITE	EMPTYP	TODO TRACED
	BOUNDS	RERANDOM	TODO READER	EMPTY?	TODO STEPPED
	SETBOUNDS	FORM	TODO WRITER	EQUALP	TODO PROCEDURES
	FILLED	BITAND	TODO SETREADPOS	EQUAL?	TODO PRIMITIVES
	LABEL	BITOR	TODO SETWRITEPOS	NOTEQUALP	TODO NAMES
	SETLABELHEIGHT	BITXOR	TODO READPOS	NOTEQUAL?	TODO PLISTS
	TEXTSCREEN	BITNOT	TODO WRITEPOS	BEFOREP	TODO ARITY
	TS	ASHIFT	TODO EOFP	BEFORE?	TODO NODES
	FULLSCREEN	LSHIFT	TODO EOF?	.EQ	TODO PRINTOUT
	FS	AND	TODO KEYP	MEMBERP	TODO PO
	SPLITSCREEN	OR	TODO KEY?	MEMBER?	TODO POT
	SS	NOT	TODO CLEARTEXT	SUBSTRINGP	TODO ERASE
	SETSCRUNCH	+	TODO CT	SUBSTRING?	TODO ER
	SHOWNP	*	TODO SETCURSOR	NUMBERP	TODO ERALL
	SHOWN?	/	TODO CURSOR	NUMBER?	TODO ERPS
	SCREENMODE	<	TODO SETTEXTCOLOR	VBARREDP	TODO ERNS
	TURTLEMODE	>	TODO SETTC	VBARRED?	TODO ERPLS
	LABELSIZE	=	TODO INCREASEFONT	COUNT	TODO BURY
	NO MATRIX	<=	TODO DECREASEFONT	ASCII	TODO UNBURY
	PENDOWN	>=	TODO SETTEXTSIZE	RAWASCII	TODO BURIEDP
	PD	<>	TODO TEXTSIZE	CHAR	TODO BURIED?
	PENUP		TODO SETTEXTFONT	MEMBER	TODO TRACE
	PU		TODO FONT	LOWERCASE	TODO UNTRACE
	PENPAINT		TODO ALLFONTS	UPPERCASE	TODO TRACEDP
	PPT		TODO CURSORINSERT	STANDOUT	TODO TRACED?
	PENERASE		TODO CURSOROVERWRITE	PARSE	TODO STEP
	PE		TODO CURSORMODE	RUNPARSE	TODO UNSTEP
	PENREVERSE		TODO WAIT		TODO STEPPEDP
	PX				TODO STEPPED?
	SETPENCOLOR				TODO EDIT
	SETPC				TODO ED
	ALLCOLORS				TODO EDITFILE
	SETPALETTE				TODO SAVE
	SETPENSIZE				TODO LOAD
	SETBACKGROUND				TODO HELP
	SETBG				TODO FOO
	PENDOWNP				TODO SETFOO
	PENDOWN?
	PENMODE
	PENCOLOR
	PC
	PALETTE
	PENSIZE
	BACKGROUND
	BG
	SAVEPICT
	LOADPICT
	SVGPICT
	MOUSEPOS
	CLICKPOS
	BUTTONP
	BUTTON?
	BUTTON

The differences between QLogo and UCBLogo are described in the nuances section below.

Here are the nuances:

Colors can be specified in one of five ways (instead of two):

1. as a palette index (0 to 100), same as UCBLogo
2. as a list of three numbers, one for each of red, green, blue: [0 0 0] is black, [100 100 100] is white, also same as UCBLogo.
3. as a list of four numbers, similar to Option 2 above, with the fourth value being transparency (or “alpha”). 100 is fully opaque, and 0 means fully transparent.
4. as a named color from the X Color Database, e.g. white or lemonchiffon. The list of color names can be retrieved using the ALLCOLORS command or from the X Color database found here: https://en.wikipedia.org/wiki/X11_color_names
5. as a hex RGB triplet, preceded by “#”, and followed by 3, 6, 9, or 12 hexadecimal digits. For example, each of the following produces the color red: #f00, #ff0000, #fff000000, and #ffff00000000.

Changes in font properties (size, color, family) do not affect characters already printed.

This enables multiple colors and fonts on the same console.

QLogo does not look for nor automatically load STARTUP.LG.

COMMANDLINE contains **ALL** of the parameters used to start qlogo instead of just the ones that appear after a hyphen.

If ERRACT is set and its size is greater than zero, then any errors execute PAUSE.

Garbage collection is on-the-fly.

Memory is freed the moment a word/list/array is no longer needed. GC and .SETSEGMENTSIZE are provided for compatibility, but are no-ops.

No scrunching.

UCBLogo provided a scrunch to compensate for older CRT screens with non-square pixels. This enabled turtle operations to maintain consistent physical height-width. The drawback is that some orientation queries are inaccurate. SCRUNCH and SETSCRUNCH are no-ops.

SAVEPICT saves a copy of the canvas in the format given by the filename’s extension.

For example: SAVEPICT "MY_PICTURE.PNG will save in PNG format.

QLogo can save an image in the following formats: BMP, JPG/JPEG, PNG, PPM, XBM, and XPM

WINDOW no longer simply allows the turtle to run away from the canvas.

WINDOW now grows the canvas to accommodate the turtle’s position.

There is no facility yet for translation/internationalization.

All the strings used in QLogo source code can be translated, but no translations have been made.

QLogo supports Unicode characters.

The CHAR command can take a Unicode character as a parameter. Similarly, the ASCII command and RAWASCII command can report the Unicode value of a character.

Unicode values are stored as 16-bit integers. Thus, the maximum value that CHAR can take is 65535.

Since ASCII is a subset of Unicode, the behavior of CHAR, ASCII and RAWASCII are the same as in UCBLogo for ASCII characters.

The following commands are not implemented:

SETMARGINS:

The original purpose of the command was to enable text to be visible on projectors which cut off outer boundaries of a computer screen. Projectors and monitors produced in recent years show all of the computer screen. In addition, QLogo is a windowed application so an instructor or presenter can move the window to a different position.

FILL:

One of the user interface principles for QLogo is that the canvas should be device resolution-independent. When the QLogo window is resized or the separator between the text and the graphics is moved then the graphics will be redrawn with the new dimensions.

The Flood Fill algorithm depends on specific pixels which means that what is filled can change dramatically depending on the size of the canvas.

The other reason is that the Flood Fill algorithm can slow down window resizing. FILL is still available.

EPSPICT:

This is replaced by SVGPICT. See below.

CSLSLOAD:

Not implemented yet.

SETCSLSLOC:

Not implemented yet.

SETEDITOR:

Psychi has its own built-in editor. If you run the qlogo program from a command line, such as in a terminal, no editor is available.

SETLIBLOC:

Not implemented. QLogo uses a SQLite database to store its standard library. You can use the setlibloc command line parameter to tell qlogo where to find the SQLite database if it is in a different location than where qlogo expects it.

SETHELPLOC:

Not implemented. QLogo uses a SQLite database to store its help text. You can use the sethelploc command line parameter to tell qlogo where to find the SQLite database if it is in a different location than where qlogo expects it.

SETTEMPLOC:

QLogo doesn’t create temporary files.

NOREFRESH and REFRESH:

QLogo is designed from the ground up to have a very responsive user interface. The canvas will always redraw itself whenever the window is resized.

SETPENPATTERN and PENPATTERN:

This isn’t implemented yet because I haven’t yet decided what kinds of patterns are wanted or useful.

The following variables have no special meaning:

REDEFP:

Qt has strong support for internationalization, but in QLogo it is only partially implemented. Internationalization will be supported soon.

USEALTERNATENAMES:

Qt has strong support for internationalization, but in QLogo it is only partially implemented. Internationalization will be supported soon.

The following commands are NEW:

SVGPICT has been added and is a replacement for EPSPICT.

SVGPICT will save the image on the canvas in Scalable Vector Graphics format.

ALLFONTS:

Returns a list of all the fonts available on your system.

ALLCOLORS:

Returns a list of all the named colors that QLogo knows about.

TIME:

This is mostly for my own curiosity and for debugging. TIME will take one parameter, a list, which it will execute. A timer will start when the list is executed and then stop when the list is finished. The total running time of the list will be printed. The output will be whatever the list outputs, if anything.

MARK:

This is for debugging memory management. MARK will take one parameter, set a flag on it, and output that parameter. At the moment it is marked, a debugging message will be printed out. Later, if/when the item is deleted, another debugging message will be printed.

CURSORINSERT:

Sets cursor to insert mode in QLogo. This is the default.

CURSOROVERWRITE:

Sets cursor to overwrite mode in QLogo.

CURSORMODE:

Outputs either INSERT or OVERWRITE.

STANDOUT:

This works in the QLogo GUI by switching the font’s foreground and background colors. It isn’t implemented for text terminals.

SETBOUNDS:

The drawing canvas in Psychi is designed to be resolution independent. The user can stretch and resize the GUI window and its components without needing interaction or permission from the QLogo program. Therefore, the best way for the programmer to have control and the GUI to have responsiveness is to set the bounds programmatically. The GUI then can squeeze or stretch the canvas to fit the window as needed.

The coordinate system of the drawing canvas is Cartesian: the Origin [0,0] is always in the center. The range of the X-coordinate is between -boundX and boundX. The range of the Y-coordinate is between -boundY and boundY. For example, a bound set at [350 150] means that the turtle is visible if its X-coordinate is between -350 and 350 and its Y-coordinate is between -150 and 150. See also BOUNDS.

BOUNDS:

Outputs a list of two numbers giving the maximum bounds (x,y) of the canvas.

FILEDIALOG:

Provides the user with a file dialog to select a file. The file path is returned as a string.

The following commands are slightly different:

LPUT and FPUT:

When using the Word form of LPUT and FPUT, there is no single-character limitation. I’m not sure why that limitation is necessary in UCBLogo.