Modules

Introduction

Before we go any further, we need to finally learn one VERY important thing – modules! They are used to organize your code into multiple files and load various libraries.
You have already seen them: std::puts that we used everywhere, std is a module too!

Exporting

Module's variables have to come from... somewhere. When you write a Wi script you need to explicitly export a bunch of variables via export statement – only they will be available when importing that script as a module. Typically, exporting is done at the end of a Wi script. Let's create a script called b.wi:

%% b.wi
x := 10;
y := 20;
z := 30;

export {
    x, y
};

You can export only global variables.
Only x and y will be available from outside this script, z won't since we didn't export it!

Importing

Let's create our main script, called a.wi, and import b.wi using the import statement:

%% a.wi
b := import "b";

You don't need to write .wi in import, Wi handles it automatically. Now, we can access x and y via ::!

%% a.wi
b := import "b";
std::puts(b::x);
std::puts(b::y);

However, if we try to access z:

%% a.wi
b := import "b";
std::puts(b::x);
std::puts(b::y);
std::puts(b::z);

We get an error:

10
20
runtime error: variable z was not exported from module b.wi
   --> a.wi:5 in main function

So don't forget to export-what-you-need!

Paths are resolved relative to the directory of the script that contains the import (absolute paths work too), and every module is loaded only once – importing it again gives you the same module. For import "b", Wi looks for b.wi, then b/init.wi, then the same two inside the lib/wi folder next to the bin folder your Wi executable lives in.
If no script exists, Wi tries to load a library (b.so on Linux, b.dll on Windows), first next to the importing script and then in lib/wi. Foreign libraries are not supported on other platforms. You can clearly see this if you try to import an unexistent script:

%% a.wi
c := import "c";

Output is:

compile error: failed to import module c
   no script c.wi
   no script c/init.wi
   no script /home/cyxigo/wi/lib/wi/c.wi
   no script /home/cyxigo/wi/lib/wi/c/init.wi
   failed to load library ./c.so: cannot open shared object file: No such file or directory
   failed to load library /home/cyxigo/wi/lib/wi/c.so: cannot open shared object file: No such file or directory
   |
 2 | c := import "c";
   |              ^
   --> a.wi:2:14

Note

Wi used to have two separate syntaxes for script and library importing, being require and load!

Next: Error Handling