I construct a function named find-all to find all indexes of a given item in a series by "recursive".
The first calling of find-all gives the right output. However from the second calling, all outputs are appended together.
find-all: function [series found][
result: []
either any [empty? series none? s-found: find series found]
[result]
[append result index? s-found
find-all next s-found found]
]
;; test:
probe find-all "abcbd" "b" ;; output [2 4] as expected
probe find-all [1 2 3 2 1] 2 ;; output [2 4 2 4]
Since variables inside a function created with function are local, why does the value of variable result is still there during later funtion callings, which cause the result of the sencond calling of find-all does not begin with []?
And what is the correct recursive way to achieve this funciton?
The answer is evident if you inspect find-all after making these two calls:
>> ?? find-all
find-all: func [series found /local result s-found][
result: [2 4 2 4]
either any [empty? series none? s-found: find series found]
[result]
[append result index? s-found
find-all next s-found found
]
]
result is an indirect value, and its data buffer is stored on a heap. The data gets preserved between the calls and accumulated, because you do not re-create it with copy — result being local to function's context is unrelated to that.