The loop for construct in common LISP is used to iterate over an iterable, similar to the for loop in other programming languages. It can be used for the following:
- This is used to set up variables for iteration.
- It can be used for conditionally terminate the iteration.
- It can be used for operating on the iterated elements.
The loop For construct can have multiple syntaxes.
Syntaxes:
- To iterate over a list:
(loop for variable in input_list do (statements/conditions) )
Here,
- input_list is the list that is to be iterated.
- The variable is used to keep track of the iteration.
- The statements/conditions are used to operate on the iterated elements.
- To iterate over the given range:
(loop for variable from number1 to number2 do (statements/conditions) )
Here,
- The number1 is the starting number and number 2 is the ending number from the range.
- The variable is used to keep track of the iteration.
- The statements/conditions are used to operate on the iterated elements.
Example: LISP Program to print numbers in a range
Lisp
;range from 1 to 5
( loop for i from 1 to 5
;display each number do (print i)
) |
Output:
1 2 3 4 5
Example 2: LISP Program to iterate elements over a list.
Lisp
; list with 5 numbers
( loop for i in '( 1 2 3 4 5 )
;display each number do (print i)
) ; list with 5 strings
( loop for i in '(JAVA PHP SQL HTML CSS)
;display each string do (print i)
) |
Output:
1 2 3 4 5 JAVA PHP SQL HTML CSS
Example 3: LISP Program to iterate each number from range and perform increment and decrement operations.
Lisp
; list with 5 numbers
( loop for i in '( 1 2 3 4 5 )
;display each number by incrementing each number by 5
do (print (incf i 5 ))
) ; list with 5 numbers
( loop for i in '( 1 2 3 4 5 )
;display each number by decrementing each number by 5
do (print (decf i 5 ))
) |
Output:
6 7 8 9 10 -4 -3 -2 -1 0
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