Repetition
Functions
Now we come to the
repetition functions. They are very important. Repetition functions
are often used in AutoLISP programs.
Here they are:
WHILE
Function
(while
(<test> <expression> …)
This
function performs a test at the beginning. If the test gives nil,
then the expressions are evaluated.
Example:
(defun
c:numbr (/ nr)
(setq
nr 1)
(while
(<= nr 5)
(princ
"\nNumber: ")
(princ
nr)
(setq
nr (1+ nr))
)
(princ)
)
(c:numbr)
At
the start of the AutoLISP program the variable NR is given the value
1. The value of the variable is tested at the beginning of the WHILE
function.
As
long as the value is less or equal to five, then the expressions in
the WHILE function are evaluated.
This
is given back by the AutoLISP program:
Number:
1
Number:
2
Number:
3
Number:
4
Number:
5
Repeat
Function
(repeat
<number> <expression> …)
Now
the number of repetitions can be specified.
Example:
(princ
"\n")
(defun
c:repfc ()
(repeat
4
(princ
"-")
)
(princ)
)
(c:repfc)
This
is given back by the AutoLISP program:
----
Foreach
Function
(foreach
<name> <list> <expression> …)
This
function goes through a list and gives every element of the list a
name. The expression is performed for every name.
Example:
(foreach
n (list 1 2 3) (* n 2))
The
AutoLISP line gives back 6. The number 3 is multiplied with 2.
Exercise:
We
have been talking about predicates, test functions and repetition
functions. Here is an exercise to use what has been taught.
Write
the SLINE AutoLISP program. The following prompts will show up:
Command:
SLINE
Color/Linetype/<first
point>: C
Color:
1
Color/Linetype/<first
point>: L
Linetype:
Hidden
Color/Linetype/<first
point>: 100,100
Close/<next
point>: 300,300
Close/<next
point>: C
Command:
