iter()

iter(<list>, <pattern>[, <delimiter>[, <output separator>]])

For each word in <list>, iter() evaluates <pattern> once, and returns a list of the results of those evaluations. Words in <list> are separated by <delimiter>, if given, and spaces if not. Words in the resulting list are separated by the given <ouput separator>, or a space if no output separator is given.

Prior to each evaluation, every occurrence of the string ”##” in <pattern> is replaced with the current word from <list>. However, because this replacement occurs before evaluation, it cannot be used well in nested iter()s, and should not be used on user input or untrusted <list>s, as the word will be evaluated. Instead, you can use the %iX substitution, or the itext() function. The substitution ‘%iL’ refers to the outermost iter of the current expression, and is intended to replace ##.

The string ”#@” will be replaced with the position of the current word in <list>. Like ”##”, the replacement occurs before substitution. Use the inum() function for nested iter()s.

If you nest iter()s, ## and #@ refer to the first/outermost iter(). The ilev() function can be used to get the current iter() nesting level.

parse() is an alias for iter().

::: seealso

Iteration examples

Examples:

say iter(This is a test string., strlen(%i0))
You say, "4 2 1 4 7"

> say iter(lnum(5), mul(add(%i0,#@),2))
You say, "2 6 10 14 18"

> say iter(lexits(here), name(%i0) (owned by [name(owner(%i0))]))
You say, "South (owned by Claudia) North (owned by Roy)"

> &STRLEN_FN me=strlen(%0)
> say iter(This is a test string., u(STRLEN_FN, %i0))
You say, "4 2 1 4 7"

Since this example just evaluates another attribute for each element of the list, it can be done more efficiently using map():

> say map(strlen_fun, This is a test string.)

> say iter(lnum(3), %i0, ,%r)
You say, "0
1
2"

An example of why using ## instead of %i0 can be insecure, and lead to unintended evaluation:

> say iter((1\,1),add##)
You say, "2"
> say iter((1\,1),add%i0)
You say, "add(1,1)"