V/var

V/var keyword

The

var

statement declares a variable initializing it to a value.

V variable_name = value

You can declare more than one variable at a time with a tuple assignment:

F get_row_column() // this is a function returning a tuple
   ...
   R (row, col)
...
V (row, col) = get_row_column() // analogous code: `V rc = get_row_column(); V row = rc[0]; V col = rc[1]`

Partial declaration is also possible:

(V row2, col) = get_row_column() // `col` has already been declared, `row2` is declared here

or:

(row, V col2) = get_row_column() // `row` has already been declared, `col2` is declared here

To declare and initialize to some value multiple variables at once use this notation ({…}):

V a = V b = 0

To declare a constant "variable" use

-V

-var

-V constant_name = value

[{…On the one hand,

means constancy, and on the other hand it means negation (<not variable> is <constant>).}]

To reduce the amount of

var

keywords you can use a new scope. For example, this code:

-V
   n_rows = 10
   n_cols = 10
   grid_size = n_rows * n_cols
   min_words = 25

is equivalent to this:

-V n_rows = 10
-V n_cols = 10
-V grid_size = n_rows * n_cols
-V min_words = 25

V?

and

V&

V? i = ‘str’.find(‘s’)

F print_set(DefaultDict[Int, Set[Int]] &map; key)
   V& s = map[key] // `V s = map[key]` is forbidden (but you can write `V s = copy(map[key])`)

I V

I (V&? sheep = Sheep?(animal)) != N
   print(sheep.some_sheep_prop)

can be shortened {…

I -V sheep = Sheep?(animal)

is redundant also because if

animal

is of type

-Animal

, then

sheep

will be const anyway [like with

auto&

in C++ —

const auto&

is not needed in such case].
} to:

I V sheep = Sheep?(animal)
   ...

because there is no hidden copying and sharing in 11l.

And like in Swift {…}

I (V sheep = Sheep?(animal)) {...}

is forbidden.

However, in 11l this is also possible:

I T(animal) == Sheep // or `I T(animal) >= Sheep`
   print(animal.some_sheep_prop)

Also note this:

I V v = ... // `v` is like a constant reference, so
   v = ...  // this is forbidden

// And if you want `v = ...` then:
I V& v = ...   // write this
I V v = copy(...) // or this

[This may seems strange, but there is a similar behaviour in other parts of 11l:

L(el)

L(&el)

, and function arguments (which are immutable ‘by default’/‘without qualifiers’).
However, despite of

v = ...

is forbidden, you can call mutable methods of

(for the sake of convenience).]

V E

Instead of:

V&? el = map.get(key)
I el == N
   print(‘Key <’key‘> is not found!’)
   R

it is better to write:

V& el = map.get(key) E
   print(‘Key <’key‘> is not found!’)
   R

This syntax is inspired by

guard let

{…however, there is no analogue of

guard <condition>

in 11l, because you can write just

I !(<condition>)

} in Swift, but it is also a logical enough, because

V& el = map.get(key)!

is the same as:

V& el = map.get(key) E
   X NullPointerException()