README.md

For

List Comprehensions

The for expression is pretty neat, you can actually use it as a list comprehension:

doubles = for i in [1,2,3,4] -> 2*i;
doubles == [2,4,6,8]; // true

You can add a filtering clause with the if keyword:

doubles2 = for i in [1,2,3,4] if i > 2 -> 2*i;
doubles2 == [6,8]; // true

... which gets applied before the mapping part happens, ie: the comprehension above is equivalent to:

doubles2 = [1,2,3,4].filter(\i > 2).map(\2 * i);

Combining Iterables

You can also zip together, or combine, two or more lists using a comprehension:

students = ['Alice', 'Bob', 'Charlie'];
grades = [90, 88, 70];

y = for s in students,
        g in grades -> [s, g]; 

y == [["Alice", 90], ["Bob", 88], ["Charlie", 70]]; // true

With a Block

You can also use the for expression with a block:

y = for i in 1 to 3{
        z = 2*i + 1;
    } -> z;

y == [2,4,6];

As a Statement

In case you omit the ->, the for loop will return an empty list. You can of course choose to ignore the return value of a for loop, and treat it like a statement:

for i in 1 to 3{
    print(i);
}

With Unpacking

If an iterable is made up of iterable elements, the for loop can automatically unpack each element:

studentsGrades = [["Alice", 90], ["Bob", 88], ["Charlie", 70]];
messages = for name, 
               grade in studentsGrades -> name+' got '+grade+' out of 100'; 

Evaluates to:

['Alice got 90 out of 100', 'Bob got 88 out of 100', 'Charlie got 70 out of 100']