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Looping

You can loop over a collection use for, any, or all. any/all are identical in a loop context, just use all if your loop body returns true or any if the body returns false. A loop body with multiple lines will always return false. The only time for is shorter is when body is a single line and the collection needs parentheses around it to loop over with all/any. Examples:

for(i in 1..10)System.print(i)
// Is shorter than
(1..10).all{|i|System.print(i)}

a.all{|i|System.print(i)}
// Is shorter than
for(i in a)System.print(i)

(1..10).any{|i|
i=i*3
System.print(i)
}
// Is shorter than
for(i in 1..10){
i=i*3
System.print(i)
}

In addition to using these for regular looping, any and all the return values of any and all can actually be put to use, as can related collection methods like where, map, and reduce.

Avoid variable declarations

Creating variables using var is expensive, its better to reuse variables when you can. Like in many other langs, if you are looping over a collection, you can reuse that collection's name as a variable inside the loop. Combine this with creating a short alias for Process and you will have a free variable on most argument holes. ie:

import"os"for Process as a
a.arguments.any{|b|
a=2
System.print(b*a)
}

Remember that you can assign a value to a variable that doesn't match its current type, so a string variable that you no longer need can be repurposed to an int, and so on.

Also, there is a preinitialized variable that may be useful: Fn. If you only need to use a variable's name 3 times in your code, using Fn is shorter than declaring one with var.

// Compare
Fn=1;Fn=2;Fn=3;
var a=1;a=2;a=3;

If you need a whole bunch of variables and can't get away with reuse, you may be able to save using function parameters:

Fn.new{|a,b,c,d,e,f,g,h,i,j|
a=b*c
System.print("%(a) %(b) %(c) %(d) %(e) %(f) %(g) %(h) %(i) %(j)")
}.call(1,2,3,4,5,6,7,8,9,10)

Short-Circuiting

Like many other languages, Wren supports conditional short-circuiting.

for(i in 1..100)if(i%7<1)System.print(i)
// is the same as
for(i in 1..100)i%7<1&&System.print(i)