add example 02 to mers_lib

mers/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mers"
-version = "0.4.0"
+version = "0.5.0"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 description = "dynamically typed but type-checked programming language"

mers_language_server/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-mers_lib = { path = "../mers_lib", features = ["parse"] }
+mers_lib = "0.5.0"
 tokio = { version = "1.34.0", default-features = false, features = ["macros", "rt", "io-std"] }
 tower-lsp = "0.20.0"
 line-span = "0.1.5"

mers_lib/examples/02_own_variable.rs

@@ -0,0 +1,60 @@
+use std::sync::Arc;
+
+use mers_lib::{
+    data::{self, Data, MersType, Type},
+    errors::CheckError,
+    prelude_compile::{parse, CompInfo, Config, Source},
+};
+
+fn main() {
+    eprintln!("This is valid:");
+    run("my_custom_var.debug.rust_func.debug".to_owned()).unwrap();
+    eprintln!();
+
+    eprintln!("This is not:");
+    let e = run("5.rust_func".to_owned()).err().unwrap();
+    eprintln!("{e}");
+}
+fn run(src: String) -> Result<(), CheckError> {
+    let mut source = Source::new_from_string(src);
+    let srca = Arc::new(source.clone());
+    let parsed = parse(&mut source, &srca)?;
+
+    // Add our custom variables to the `Config`
+    let (mut i1, mut i2, mut i3) = Config::new()
+        .bundle_std()
+        .add_var(
+            "my_custom_var".to_owned(),
+            Data::new(data::string::String(format!("my custom value!"))),
+        )
+        .add_var(
+            "rust_func".to_owned(),
+            Data::new(data::function::Function::new(
+                |arg| {
+                    // If the input is a string, the output is a string.
+                    // Otherwise, the function is used incorrectly.
+                    if arg.is_included_in(&data::string::StringT) {
+                        Ok(Type::new(data::string::StringT))
+                    } else {
+                        // Wrong argument type. The code won't compile and this is the error message shown to the user.
+                        Err(format!("Can't call rust_func with non-string argument {arg}!").into())
+                    }
+                },
+                |arg| {
+                    let arg = arg.get();
+                    let arg = &arg
+                        .as_any()
+                        .downcast_ref::<data::string::String>()
+                        .unwrap()
+                        .0;
+                    Data::new(data::string::String(arg.chars().rev().collect()))
+                },
+            )),
+        )
+        .infos();
+
+    let compiled = parsed.compile(&mut i1, CompInfo::default())?;
+    compiled.check(&mut i3, None)?;
+    compiled.run(&mut i2);
+    Ok(())
+}