Difference between 'forea

muthu123 · 发表于 2022-7-6 09:24:16

What is the difference between the function 'foreach and 'mapcar with lambda?

Can you explain with clear example?

MSasu · 发表于 2022-7-6 09:33:54

Please check this tutorial: http://www.afralisp.net/autolisp/tutorials/mapcar-and-lambda.php.

Regards,

muthu123 · 发表于 2022-7-6 09:39:14

Thank you so much.

Now i can understan mapcar, Lambda and apply.

But still i need some more examples for the function 'foreach.

MSasu · 发表于 2022-7-6 09:41:28

You welcome! That tutorial contains a FOREACH example also.

For more FOREACH function's examples, I'm sure that you can find a lot by simply searching the forum.

Regards,

Lee Mac · 发表于 2022-7-6 09:46:15

The foreach loop uses a symbol to represent each element in the provided list argument, and evaluates the provided expressions within the foreach loop on every element in the list, for example:

copy

(foreach item '(0 1 2 3 4 5) (setq lst (cons (1+ item) lst)))

Will return:

copy

(6 5 4 3 2 1)

Each element in the list is bound to the symbol 'item' and then the expressions are evaluated using this variable.

Hope this helps,

Lee

MSasu · 发表于 2022-7-6 09:52:54

No offence, but don’t you belive that using CONS to show the result may be confusing for a beginner? I mean the result list is reverted and have to figure out why from just adding 1 to each item? How about using LIST or PRINT?

copy

(foreach item '(0 1 2 3 4 5)(setq lst (append lst (list (1+ item))))(print (1+ item)))

Regards,

Lee Mac · 发表于 2022-7-6 09:58:43

Fair point - yours is a better example.

Freerefill · 发表于 2022-7-6 10:04:02

Lee has a habit of being awesome 24/7. It's a little hard for newbies to comprehend.

Lee Mac · 发表于 2022-7-6 10:10:34

Haha you flatter me too much

ketxu · 发表于 2022-7-6 10:14:36

And please tell me what order do function item in list in Foreach ? The first to the Last or Last to First ?
Ex : (foreach x '( 1 2 3 4 5) (1+ x)...) : the order is (1+ 1) (1+ 2) (1+ 3)... or (1+ 5) (1+ 4) (1+ 3)...
( Srr, my English not well )

P/S 2 : Srr, i'd tested and found that foreach start from the first to last element ^^

[编程交流] Difference between 'forea

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