The Workspace
All commands related to the workspace.
ABOUT
A user-defined procedure to display information about your program.
Syntax
ABOUT
Description
ABOUT is a user-defined procedure that Logo calls when the user selects the “About…” menu item. To display information about your program, write this procedure and let it either PRINT some informative text, or display an ALERT box containing this information.
Example
TO ABOUT IGNORE ALERT “|This is my precious app!| END
ALIAS
Defines alias names.
Syntax
ALIAS old-name new-name
Description
ALIAS defines a new procedure name with the same meaning as an existing procedure name. The new name is an alias name for the existing name and behaves exactly like that name. Values or properties stored as a name are not aliased.
ALIAS is handy for defining shortcuts or translations of commands.
BYE
Also: QUIT, EXIT
Ends Logo.
Syntax
BYE
Description
BYE ends the Logo session and logs you out. The command names QUIT and EXIT perform the same function.
CHAR
Converts a number into a Unicode character.
Syntax
CHAR number
Description
CHAR reports the character whose Unicode code is the input. The input number can be from 0 through #H10FFF. To output the Unicode code corresponding to an input character, use UNICODE.
Use caution when saving a Logo name or procedure that contains unprintable characters, like characters with a value of less than 32. Logo saves them as is without escaping them. If you, for example, save a value that contains a newline character (CHAR 10), then Logo may not be able to read that file correctly.
Example
CHAR 20013 Result: 中
CLEARTEXT
Also: CT
Clears the Listener panel.
Syntax
CLEARTEXT
Description
CLEARTEXT clears all text and places the cursor in the upper left corner of the Listener panel. CLEARTEXT is the same as the command TYPE CHAR 12.
Example
REPEAT 5 [PR [GOOD EVENING]] CLEARTEXT
DATE
Reports the date.
Syntax
DATE
Description
DATE reports the current date as a four-element list in the form [day month year dayofweek]. The dayofweek is a number from 1 to 7, starting at Sunday.
Example
DATE Result: [21 11 2019 5]
FULLSCREEN
Also: FS
Switches to the Full Screen perspective
Syntax
FULLSCREEN
Description
FULLSCREEN minimizes the Listener panel and maximizes the Graphics canvas.
Example
FS
HELP
Displays help for a command.
Syntax
HELP commandname
Description
HELP displays the help file for the requested command.
Example
HELP “FORWARD
LMAKE
Also: LOCALMAKE
Create and set a local name.
Syntax
LMAKE varname value
Description
LMAKE works in two ways. The first time LMAKE varname value is used in
a procedure, Logo creates a new local name varname and assigns value
to the local varname. This is the same as LOCAL varname MAKE varname
value. For all subsequent uses of LMAKE varname value, Logo just uses
the existing local varname. This the same as MAKE varname value. The
important thing to consider about LMAKE is that it ensures that the
variable being referenced is local (by either creating a new local
variable or using an existing local variable).
See also LOCAL, MAKE and THING.
LOAD
Loads a file into Logo.
Syntax
LOAD filename
LOAD filename.ext
LOAD [extensions-list]
(LOAD)
Description
LOAD transfers the contents of the file specified by its input from the Workspace area to the Logo workspace. The entire file is treated as though it were typed from the keyboard. LOAD throws an error if the file is not successfully loaded.
If no file name extension is specified, LOAD loads the file filename.LGO. To load a file that has no extension, a period is necessary after the filename.
If you use a list of file extensions as the file name, or use the command without inputs, Logo displays a Select File dialog with the list of files limited to the ones matching the list of extensions. Logo also supports old-style Terrapin Logo typelists, but their use is not recommended. See SELECT.FILE for more information.
LOAD is not available in a published Logo application.
MAKE
Assigns a value to a name.
Syntax
MAKE name object
Description
MAKE defines a variable using the name of the first input and assigns the second input as the value of that variable. Once you have created the variable, you may obtain its contents by using :name. Think of the colon (:) as the value of name. To keep a variable local to the procedure in which MAKE is used, see LOCAL or LMAKE.
Remember that all local names of a procedure are visible to any procedure; a MAKE command may, therefore, set a name that is local to a procedure that is calling the current procedure if you use MAKE inside a procedure. See also NAME and THING.
Example
MAKE “NUMBER 73 :NUMBER Result: 73
MILLISECONDS
Outputs the number of milliseconds spent.
Syntax
MILLISECONDS
Description
MILLISECONDS outputs the number of milliseconds spent since the document loaded. MILLISECONDS can be used to track execution times. The accuracy of this timer is supposed to be at least 5 microseconds, but depends on the browser and operating system. Also, it is not guaranteed that the timer started running when the document has been loaded.
NAME
Assigns a value to a name.
Syntax
NAME object name
Description
NAME defines a variable by assigning the value of the first input to the name of the second input. Once you have created the variable, you may obtain its contents by using :name. Think of the colon (:) as the value of name. NAME is equivalent to MAKE except that inputs are in reverse order. See also LOCAL.
PHELP
Displays help for a property.
Syntax
PHELP propertyname
Description
PHELP displays the help file for the requested property name.
Example
HELP “ALIGN
QUOTE
Quotes its input.
Syntax
QUOTE word
Description
QUOTE quotes its input. Lists are returned unchanged.
Example
MAKE “FIRSTNAME “JOHN :FIRSTNAME Result: JOHN QUOTE :FIRSTNAME Result: “JOHN
RESTART
Erases everything and restarts Logo.
Syntax
RESTART
(RESTART TRUE)
Description
RESTART erases all Logo contents and reinitializes Logo. When RESTART is used, a confirmation dialog box appears. If RESTART and its optional argument TRUE are enclosed in parentheses, Logo will be restarted without the appearance of the confirming dialog!
SAVE
Saves the workspace to disk.
Syntax
SAVE filename
SAVE [extensions-list]
(SAVE)
Description
SAVE saves the contents of the Logo workspace to a storage medium area. This includes all defined procedures and names, the “PREFS properties, and all buried names. Workspace files are saved as text files.
If no file name extension is specified, SAVE saves the file with the name filename.LGO. To save a file that has no extension, a period is necessary after the filename.
To save the entire Logo environment, including turtles, panel layouts, and the editor contents, select “File/Save…” from the menu and select “Save a Logo environment file”. Note that this command is only available to registered users of Logo.
If you use a list of file extensions as the file name, or use the command without inputs, Logo displays a Select File dialog with the list of files limited to the ones matching the list of extensions. Logo also supports old-style Terrapin Logo typelists, but their use is not recommended. See SELECT.FILE for more information.
SAVE is not available in a published Logo application.
SPLITSCREEN
Also: SS
Makes both the Listener panel and the Graphics canvas visible.
Syntax
SPLITSCREEN
Description
SPLITSCREEN makes both the Listener panel and the Graphics canvas visible.
See also TEXTSCREEN and FULLSCREEN.
Example
SS
TEXTSCREEN
Also: TS
Minimizes the Graphics canvas and maximizes the Listener panel.
Syntax
TEXTSCREEN
Description
TEXTSCREEN minimizes the Graphics canvas and maximizes the Listener panel.
See also SPLITSCREEN and FULLSCREEN.
Example
TS
THING
Reports the value of a name.
Syntax
THING word
Description
THING reports the value associated with the variable named in the input. THING is the Logo primitive that does the same job as : (dots). It can be used to give a variable a second level of evaluation. A variable name could, for example, be passed in to a procedure, and the procedure obtains its value with the THING command. Remember that Logo makes all names in a procedure visible to a procedure that this procedure calls. Therefore, getting a value may result in getting the value of a name that is local to a calling procedure.
Example
MAKE “COLOR “BLUE MAKE “BLUE “AQUAMARINE THING “COLOR Result: BLUE THING :COLOR Result: AQUAMARINE THING “BLUE Result: AQUAMARINE THING :BLUE :AQUAMARINE is not a name
TIME
Outputs the time.
Syntax
TIME
Description
TIME reports the current time as a list of three numbers in the form [hour minute second]. The hours are in 24-hour format. See also DATE.
Example
TIME Result: [10 35 50]
UNICODE
Converts a character into its Unicode value.
Syntax
UNICODE character
ASCII character
Description
UNICODE reports the Unicode value of its input. The Unicode standard is a standard code for representing numbers, letters and symbols. If its input is a word, UNICODE reports the UNICODE value of the first character in the word. UNICODE reports an integer value. The input must contain at least one character. The character can be a letter, number or special character. To output the character corresponding to an UNICODE code input, use CHAR.
The alias ASCII is maintained for backward compatibility.
Example
UNICODE “中 Result: 20013
VERINFO
Outputs Logo version information as a list.
Syntax
VERINFO
Description
VERINFO reports information about the version of Logo that is currently running as a list. The elements are major version number, minor version number, subrelease number, the name of the Logo program, the build date as a string, and the name of the operating system.
Example
VERINFO Result: [0 0 1 Terrapin Logo Sat, 01 Aug 2015 08:44:46 GMT Windows]
VERSION
Also: VER
Outputs the Logo version.
Syntax
VERSION
Description
VERSION reports information about the version of Logo that is currently running.
Example
VERSION Result: Terrapin Logo V0.0.1 Sat, 01 Aug 2015 08:44:46 GMT
WHEN
Monitors a change to a Logo property or to a Logo event.
Syntax
WHEN [name propertyname compare-to value] [runlist]
WHEN [name propertyname] [runlist]
WHEN [name] [runlist]
WHEN [name propertyname compare-to value] []
WHEN [name propertyname] []
WHEN [name] []
(WHEN [property-condition])
(WHEN)
Description
The WHEN command monitors changes to a Logo property, or a change to the Logo environment. Its first input tells WHEN what to watch, and the second input is a list of Logo commands that logo should run when Logo detects the condition to watch,
If the second list is empty, Logo turns off monitoring the condition described in the first input.
The first input is a list of one to four elements.
If there is only one element, it is the name of the property list to watch; in that case, WHEN triggers the event if any of the property list’s properties change.
If there are two elements, Logo monitors changes to the supplied
property, and runs the runlist if there are any changes to the property.
To watch the light sensor of an InO-Bot, for example, the list would be
[INOBOT LIGHT].
If there are three or four elements, the last two elements are a
comparison operator (one of =, <>, <=,
<, >=, > or any of its aliases), and the
value to compare against. For example, if the
APPENDMENUITEM has been used to create a menu
item with the ID TEST, the list [MENU TEST] would cause Logo to run
the runlist whenever the user selects that menu item. For InO-Bot’s
light sensor to trigger a runlist when the light level is above 0.5, the
list would be [INOBOT LIGHT > 0.5].
Note that Logo runs the runlist only once when it compares a value with the <=, <, >=, or > operators. Logo will wait for the comparison to become FALSE before running the runlist again when the condition matches again. This means for the InO-Bot example that Logo would run the runlist once the light level is above 0.5, then wait the light level to drop below 0.5 before checking the level again. This prevents Logo from running the runlist anytime the light level is above 0.5.
Note that you do not use quotes inside a list. For example, if you want
Logo to run a runlist when the key “A” is pressed, use [WHEN KEY = A],
not [KEY = “A].
You can issue as many WHEN commands as you need to monitor a single property.
A more detailed explanation and many more examples can be found at the page WHEN Something happens.
Note that WHEN stops running when the program terminates. To make Logo monitor changes continuously even after the program has ended, use the WHENEVER command. This makes sense, for example, when you monitor menu item selections.
Whenever Logo throws a runtime error that is reported to the Listener, Logo stops all monitoring.
The WHEN command with a single input is the same as the WHEN command with an empty runlist; it stop processing of the condition described in its input.
WHEN without any inputs stops all processing that was created with the WHEN command. It does not stop the processing of runlists defined with the WHENEVER command.
Example
; Turn InO-Bot’s headlights on when it becomes dark WHEN [INOBOT LIGHT < 0.3] [PPROP “INOBOT “LIGHTS [1 1]] ; Turn InO-Bot’s headlights off when it becomes bright WHEN [INOBOT LIGHT >= 0.3] [PPROP “INOBOT “LIGHTS [0 0]]
WHENEVER
Monitors changes to a Logo property or to a Logo event.
Syntax
WHENEVER [name propertyname compare-to value] [runlist]
WHENEVER [name propertyname] [runlist]
WHENEVER [name] [runlist]
WHENEVER [name propertyname compare-to value] []
WHENEVER [name propertyname] []
WHENEVER [name] []
(WHENEVER [property-condition])
(WHENEVER)
Description
The WHENEVER command causes Logo to monitor a property of a change to the Logo event. It is identical to the WHEN command, but Logo does not stop monitoring when the program that issued the WHENEVER command ends. Logo continues to monitor the condition until a WHENEVER command is entered with the very same condition, but an empty runlist.
Use WHENEVER to monitor changes that need to be monitored outside of a program, like the user selecting a menu item, or a Bluetooth device being connected.
When Logo throws a runtime error that is reported to the Listener, it
does not affect runlists defined with the WHENEVER command. Use
(WHENEVER) to halt processing for these runlists. It does not stop
processing of runlists that were defined with the WHEN command.
Example
; Append the menu item “Testing” with the ID “TEST” to the Help menu APPENDMENUITEM “HELP “|Testing| “TEST ; Print “TESTING anytime the user selects that item WHENEVER [MENU TEST] [PR “TESTING]