Test data or data contents.

Counts the number of items in its input.

COUNT word
COUNT list

COUNT reports the number of elements in its input. If its input is a word, COUNT reports the number of characters. If the input is a list, COUNT reports the number of elements in the list.

COUNT "ELEMENTARY
Result: 10
COUNT [ELEMENTARY]
Result: 1
COUNT [[MT. WASHINGTON] [MT. RAINIER] [MAUNA LOA]]
Result: 3

Checks whether a procedure is defined.

DEFINED? name

DEFINED? reports TRUE if the input is a name of a primitive procedure or a user-defined procedure; otherwise it reports FALSE. Compare with PROCEDURE?, which reports TRUE only if the input is a user-defined procedure, and PRIMITIVE?, which reports TRUE only if the input is a built-in command.

DEFINED? "FORWARD
Result: TRUE

Checks whether a name is empty.

EMPTY? word
EMPTY? list

EMPTY? reports TRUE if the input is the empty word (“||) or the empty list ([]); otherwise, it reports FALSE.

MAKE "FRUIT "||
EMPTY? :FRUIT
Result: TRUE
MAKE "FRUIT [PAPAYA]
EMPTY? :FRUIT
Result: FALSE

Checks for its input being a list.

LIST? object

LIST? reports TRUE if its input is a list; otherwise, it reports FALSE. See also TYPEOF, NUMBER? and WORD?.

LIST? [GREEN BLUE]
Result: TRUE
LIST? "GREEN
Result: FALSE
LIST? []
Result: TRUE

Checks its input for being a macro.

MACRO? word

MACRO? reports TRUE if the input word is the name of a Logo macro; otherwise, it reports FALSE. Compare with DEFINED?, which reports TRUE for both primitives and procedures, and PROCEDURE?, which reports FALSE for primitives and TRUE for user-defined procedures. All these commands report similarly for both buried and unburied procedures. See also .MACRO and .DEFMACRO for more information about macros.

MACRO? "FD
Result: FALSE
DEFINED? "FD
Result: TRUE

Checks if an object is part of another object.

MEMBER? word-or-list word-or-list
(MEMBER? word-or-list word-or-list TRUE)

MEMBER? reports TRUE if the first input is an element of the second input; otherwise it reports FALSE.

If the second input is a list, MEMBER? compares each element of the list. It does not scan any sub-lists, unless it is caled with a third, optional input set to TRUE.

MEMBER? "A "ABC
Result: TRUE
MEMBER? [INSIDE] [A [B [INSIDE] C] D]
Result: FALSE
(MEMBER? [INSIDE] [A [B [INSIDE] C] D] TRUE)
Result: TRUE

Checks whether its input is assigned a value.

NAME? name

NAME? reports TRUE if the input is a name of a variable; otherwise; it reports FALSE. See also TYPEOF, LIST?, NUMBER?, and WORD?.

ERASE "ANIMAL
NAME? "ANIMAL
Result: FALSE
MAKE "ANIMAL "CAT
NAME? "ANIMAL
Result: TRUE

Checks its input for being a number.

NUMBER? object

NUMBER? reports TRUE if its input is a number; otherwise it reports FALSE. Note that Logo treats quoted numbers or numbers that have been put together as numbers as well. See also LIST?, NAME?, and WORD?.

NUMBER? WORD "4 "1
Result: TRUE
NUMBER? 41
Result: TRUE
NUMBER? [41]
Result: FALSE
NUMBER? FIRST [41]
Result: TRUE
NUMBER? 4.1
Result: TRUE

Checks its input for containing a property list.

PLIST? word

PLIST? outputs TRUE if a property list exists under the given name, FALSE otherwise.

PLIST "A
Result: FALSE
PPROP "A "B "C
PLIST? "A
Result: TRUE

Checks its input for being a built-in procedure or macro.

PRIMITIVE? word

PRIMITIVE? reports TRUE if the input word is the name of a built-in Logo command or macro; otherwise, it reports FALSE. User-defined procedures or macros are not considered primitives; hence PRIMITIVE? reports FALSE when given their names as input. Compare with DEFINED?, which reports TRUE for both primitives, macros and procedures, and PROCEDURE?, which reports FALSE for primitives and TRUE for user-defined procedures and macros. All these commands report similarly for both buried and unburied procedures and macros. Remember that a macro is a special form of a procedure, see .MACRO for details.

PRIMITIVE? "FD
Result: TRUE
PROCEDURE? "FD
Result: FALSE
DEFINED? "FD
Result: TRUE

Checks its input for being a user-defined procedure.

PROCEDURE? word

PROCEDURE? reports TRUE if the input word is the name of a user-defined Logo procedure; otherwise, it reports FALSE. Compare with DEFINED?, which reports TRUE for both primitives and procedures, and PRIMITIVE?, which reports TRUE for primitives and FALSE for user-defined procedures. All these commands report similarly for both buried and unburied procedures.

TO SAY.HELLO
    PRINT "HELLO
END
SAY.HELLO defined
PRIMITIVE? "SAY.HELLO
Result: FALSE
PROCEDURE? "SAY.HELLO
Result: TRUE
DEFINED? "SAY.HELLO
Result: TRUE

Checks its input for being a word.

WORD? object

WORD? reports TRUE if its input is a word; otherwise it reports FALSE. See also LIST?, NAME?, and NUMBER?.

WORD? 123
Result: TRUE
WORD? "FD
Result: TRUE
WORD? [FD]
Result: FALSE