changed "var type = value" syntax to "var::type = value" and added the tutor (mers -t)

README.md

@@ -44,6 +44,10 @@ To run a program, just run `mers your_file.txt`. The file needs to be valid utf8
 Alternatively, run `mers -e println("Hello, file-less world")`.
 If you compiled mers in debug mode, it will print a lot of debugging information.
 
+### tutor
+
+Use `mers -t` to start the tutor, which will give you an interactive tour of the language.
+
 ### interactive mode
 
 Use `mers -i` to start interactive mode. mers will create a temporary file and open it in your default editor. Every time the file is saved, mers reloads and runs it, showing errors or the output.

mers/Cargo.toml

@@ -6,8 +6,8 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [lib]
-name = "mers"
+name = "mers_libs"
-path = "src/main.rs"
+path = "src/lib.rs"
 
 [dependencies]
 edit = "0.1.4"

mers/src/interactive_mode.rs

@@ -0,0 +1,130 @@
+/// creates a temporary file, then opens it in the user's default editor. watches the fs for changes to the file and acts upon them.
+pub mod fs_watcher {
+    use notify::Watcher;
+    use std::{
+        fs,
+        path::PathBuf,
+        thread::{self, JoinHandle},
+    };
+
+    #[derive(Debug)]
+    pub struct Error(String);
+
+    /// on each file change, recompiles and runs the code. lets people experiment with mers without having to put a file anywhere
+    pub fn playground(spawn_new_terminal_for_editor: bool) -> Result<(), Error> {
+        main(
+            spawn_new_terminal_for_editor,
+            "// Welcome to mers! (interactive mode)
+
+// put your name here, then save the file to run the script.
+your_name = \"\"
+greeting = \"Hello, {0}!\".format(your_name)
+println(greeting)
+",
+            Box::new(|temp_file: &PathBuf| {
+                println!();
+                if let Ok(file_contents) = fs::read_to_string(&temp_file) {
+                    let mut file =
+                        crate::parse::file::File::new(file_contents, temp_file.to_path_buf());
+                    match crate::parse::parse::parse(&mut file) {
+                        Ok(func) => {
+                            println!(" - - - - -");
+                            let output = func.run(vec![]);
+                            println!(" - - - - -");
+                            println!("{}", output);
+                        }
+                        Err(e) => println!("{}", e.with_file(&file)),
+                    }
+                } else {
+                    println!("can't read file at {:?}!", temp_file);
+                    std::process::exit(105);
+                }
+            }),
+        )?
+        .0
+        .join()
+        .unwrap();
+        Ok(())
+    }
+
+    /// when the file is changed, calls the provided closure with the file's path.
+    /// returns a JoinHandle which will finish when the user closes the editor and the file that is being used.
+    pub fn main(
+        spawn_new_terminal_for_editor: bool,
+        initial_file_contents: &str,
+        mut on_file_change: Box<dyn FnMut(&PathBuf) + Send>,
+    ) -> Result<(JoinHandle<()>, PathBuf), Error> {
+        let temp_file_edit = edit::Builder::new().suffix(".mers").tempfile().unwrap();
+        let temp_file = temp_file_edit.path().to_path_buf();
+        eprintln!(
+            "Using temporary file at {temp_file:?}. Save the file to update the output here."
+        );
+        if let Ok(_) = std::fs::write(&temp_file, initial_file_contents) {
+            if let Ok(mut watcher) = {
+                let temp_file = temp_file.clone();
+                // the file watcher
+                notify::recommended_watcher(move |event: Result<notify::Event, notify::Error>| {
+                    if let Ok(event) = event {
+                        match &event.kind {
+                            notify::EventKind::Modify(notify::event::ModifyKind::Data(_)) => {
+                                on_file_change(&temp_file);
+                            }
+                            _ => (),
+                        }
+                    }
+                })
+            } {
+                if let Ok(_) = watcher.watch(&temp_file, notify::RecursiveMode::NonRecursive) {
+                    let out = if spawn_new_terminal_for_editor {
+                        if let Ok(term) = std::env::var("TERM") {
+                            let editor = edit::get_editor().unwrap();
+                            eprintln!("launching \"{term} -e {editor:?} {temp_file:?}...");
+                            let mut editor = std::process::Command::new(term)
+                                .arg("-e")
+                                .arg(&editor)
+                                .arg(&temp_file)
+                                .spawn()
+                                .unwrap();
+                            (
+                                thread::spawn(move || {
+                                    // wait for the editor to finish
+                                    editor.wait().unwrap();
+                                    // stop the watcher (this is absolutely necessary because it also moves the watcher into the closure,
+                                    // which prevents it from being dropped too early)
+                                    drop(watcher);
+                                    // close and remove the temporary file
+                                    temp_file_edit.close().unwrap();
+                                }),
+                                temp_file,
+                            )
+                        } else {
+                            return Err(Error(format!("TERM environment variable not set.")));
+                        }
+                    } else {
+                        let tf = temp_file.clone();
+                        (
+                            thread::spawn(move || {
+                                edit::edit_file(temp_file).unwrap();
+                                drop(watcher);
+                                temp_file_edit.close().unwrap();
+                            }),
+                            tf,
+                        )
+                    };
+                    Ok(out)
+                } else {
+                    return Err(Error(format!(
+                        "Cannot watch the file at \"{:?}\" for hot-reload.",
+                        temp_file
+                    )));
+                }
+            } else {
+                return Err(Error(format!(
+                    "Cannot use filesystem watcher for hot-reload."
+                )));
+            }
+        } else {
+            return Err(Error(format!("could not write file \"{:?}\".", temp_file)));
+        }
+    }
+}

mers/src/lib.rs

@@ -0,0 +1,10 @@
+#![allow(unused)]
+#![allow(dead_code)]
+
+mod libs;
+mod parse;
+mod script;
+
+pub use libs::inlib::*;
+pub use parse::*;
+pub use script::{val_data::*, val_type::*};

mers/src/main.rs

@@ -1,13 +1,16 @@
+#![allow(unused)]
+#![allow(dead_code)]
+
 use std::{fs, time::Instant};
 
 use notify::Watcher as FsWatcher;
 
-pub mod libs;
+mod interactive_mode;
-pub mod parse;
+mod libs;
-pub mod script;
+mod parse;
+mod script;
+mod tutor;
 
-// necessary because the lib target in Cargo.toml also points here. TODO: update Cargo.toml to have a lib target that is separate from the bin one (=> doesn't point to main)
-#[allow(unused)]
 fn main() {
     let args: Vec<_> = std::env::args().skip(1).collect();
     #[cfg(debug_assertions)]
@@ -27,9 +30,11 @@ fn main() {
         _ => {
             if args[0].trim_start().starts_with("-") {
                 let mut execute = false;
+                let mut print_version = false;
                 let mut verbose = 0;
                 let mut interactive = 0;
                 let mut interactive_use_new_terminal = false;
+                let mut teachme = false;
                 let mut prev_char = None;
                 let mut advanced = false;
                 for ch in args[0][1..].chars() {
@@ -41,7 +46,9 @@ fn main() {
                         match ch {
                             'e' => execute = true,
                             'v' => verbose += 1,
+                            'V' => print_version = true,
                             'i' => interactive += 1,
+                            't' => teachme = true,
                             ch => {
                                 eprintln!("Ignoring -{ch}. (unknown char)");
                                 continue;
@@ -65,103 +72,29 @@ fn main() {
                         advanced = false;
                     }
                 }
+                if print_version {
+                    println!(
+                        "mers {}",
+                        option_env!("CARGO_PKG_VERSION")
+                            .unwrap_or("[[ version unknown: no CARGO_PKG_VERSION ]]")
+                    );
+                    return;
+                }
+                if teachme {
+                    tutor::start(false);
+                    return;
+                }
                 if verbose != 0 {
                     eprintln!("info: set verbosity level to {verbose}. this doesn't do anything yet. [TODO!]");
                 }
                 if interactive >= 0 {
-                    let (contents, path) = match interactive {
+                    match interactive {
-                        1 => {
+                        _ => {
                             // basic: open file and watch for fs changes
-                            let temp_file_edit =
+                            interactive_mode::fs_watcher::playground(interactive_use_new_terminal)
-                                edit::Builder::new().suffix(".mers").tempfile().unwrap();
-                            let temp_file = temp_file_edit.path();
-                            eprintln!("Using temporary file at {temp_file:?}. Save the file to update the output here.");
-                            if let Ok(_) = std::fs::write(&temp_file, []) {
-                                if let Ok(mut watcher) = {
-                                    let temp_file = temp_file.to_path_buf();
-                                    // the file watcher
-                                    notify::recommended_watcher(
-                                        move |event: Result<notify::Event, notify::Error>| {
-                                            if let Ok(event) = event {
-                                                match &event.kind {
-                                                    notify::EventKind::Modify(
-                                                        notify::event::ModifyKind::Data(_),
-                                                    ) => {
-                                                        println!();
-                                                        if let Ok(file_contents) =
-                                                            fs::read_to_string(&temp_file)
-                                                        {
-                                                            let mut file = parse::file::File::new(
-                                                                file_contents,
-                                                                temp_file.clone(),
-                                                            );
-                                                            match parse::parse::parse(&mut file) {
-                                                                Ok(func) => {
-                                                                    println!(" - - - - -");
-                                                                    let output = func.run(vec![]);
-                                                                    println!(" - - - - -");
-                                                                    println!("{}", output);
                         }
-                                                                Err(e) => println!(
-                                                                    "{}",
-                                                                    e.with_file(&file)
-                                                                ),
-                                                            }
-                                                        } else {
-                                                            println!(
-                                                                "can't read file at {:?}!",
-                                                                temp_file
-                                                            );
-                                                            std::process::exit(105);
-                                                        }
-                                                    }
-                                                    _ => (),
-                                                }
-                                            }
-                                        },
-                                    )
-                                } {
-                                    if let Ok(_) = watcher
-                                        .watch(&temp_file, notify::RecursiveMode::NonRecursive)
-                                    {
-                                        if interactive_use_new_terminal {
-                                            if let Ok(term) = std::env::var("TERM") {
-                                                let editor = edit::get_editor().unwrap();
-                                                eprintln!("launching \"{term} -e {editor:?} {temp_file:?}...");
-                                                std::process::Command::new(term)
-                                                    .arg("-e")
-                                                    .arg(&editor)
-                                                    .arg(temp_file)
-                                                    .spawn()
-                                                    .unwrap()
-                                                    .wait()
-                                                    .unwrap();
-                                            }
-                                        } else {
-                                            edit::edit_file(temp_file_edit.path()).unwrap();
-                                        }
-                                        temp_file_edit.close().unwrap();
-                                        std::process::exit(0);
-                                    } else {
-                                        println!(
-                                            "Cannot watch the file at \"{:?}\" for hot-reload.",
-                                            temp_file
-                                        );
-                                        std::process::exit(104);
-                                    }
-                                } else {
-                                    println!("Cannot use filesystem watcher for hot-reload.");
-                                    // TODO: don't exit here?
-                                    std::process::exit(103);
-                                }
-                            } else {
-                                println!("could not write file \"{:?}\".", temp_file);
-                                std::process::exit(102);
-                            }
-                        }
-                        _ => (String::new(), String::new()),
                     };
-                    parse::file::File::new(contents, path.into())
+                    return;
                 } else if execute {
                     parse::file::File::new(
                         args.iter().skip(1).fold(String::new(), |mut s, v| {

mers/src/parse/parse.rs

@@ -455,7 +455,7 @@ fn parse_statement_adv(
         let mut start = String::new();
         loop {
             fn is_delimeter(ch: char) -> bool {
-                matches!(ch, '}' | ']' | ')' | '.' | '=')
+                matches!(ch, '}' | ']' | ')' | '.')
             }
             let nchar = match file.peek() {
                 Some(ch) if is_delimeter(ch) => Some(ch),
@@ -463,6 +463,40 @@ fn parse_statement_adv(
             };
             match nchar {
                 Some(':') => {
+                    if let Some(':') = file.peek() {
+                        _ = file.next();
+                        let file_pos_before_pot_type = *file.get_pos();
+                        let parsed_type = parse_type(file);
+                        file.skip_whitespaces();
+                        if let Some('=') = file.next() {
+                            let err_equals_sign = *file.get_pos();
+                            let start = start.trim();
+                            let derefs = start.chars().take_while(|c| *c == '*').count();
+                            match parse_statement(file) {
+                                Ok(v) => break v
+                                    .output_to(start[derefs..].to_owned(), derefs)
+                                    .force_output_type(Some(match parsed_type {
+                                        Ok(v) => v,
+                                        Err(mut e) => {
+                                            e.context.push((
+                                                format!("interpreted this as an assignment to a variable with the format <var>::<var_type> = <statement>"), Some((err_start_of_statement, Some(err_equals_sign)))
+                                            ));
+                                            return Err(e);
+                                        }
+                                    })),
+                                Err(mut e) => {
+                                    e.context.push((
+                                        format!(
+                                            "statement was supposed to be assigned to variable {start}"
+                                        ),
+                                        Some((err_start_of_statement, Some(err_equals_sign))),
+                                    ));
+                                    return Err(e);
+                                }
+                            }
+                        }
+                        file.set_pos(file_pos_before_pot_type);
+                    }
                     return Ok(SStatement::new(SStatementEnum::EnumVariant(
                         start,
                         parse_statement(file)?,
@@ -484,8 +518,8 @@ fn parse_statement_adv(
                         let err_equals_sign = *file.get_pos();
                         let start = start.trim();
                         let derefs = start.chars().take_while(|c| *c == '*').count();
-                        break match parse_statement(file) {
+                        match parse_statement(file) {
-                            Ok(v) => v,
+                            Ok(v) => break v.output_to(start[derefs..].to_owned(), derefs),
                             Err(mut e) => {
                                 e.context.push((
                                     format!(
@@ -495,43 +529,8 @@ fn parse_statement_adv(
                                 ));
                                 return Err(e);
                             }
+                        };
                     }
-                        .output_to(start[derefs..].to_owned(), derefs);
-                    }
-                    // var type = statement
-                    let file_pos_before_pot_type = *file.get_pos();
-                    let parsed_type = parse_type(file);
-                    file.skip_whitespaces();
-                    if let Some('=') = file.peek() {
-                        file.next();
-                        let err_equals_sign = *file.get_pos();
-                        let start = start.trim();
-                        let derefs = start.chars().take_while(|c| *c == '*').count();
-                        break match parse_statement(file) {
-                            Ok(v) => v,
-                            Err(mut e) => {
-                                e.context.push((
-                                    format!(
-                                        "statement was supposed to be assigned to variable {start}"
-                                    ),
-                                    Some((err_start_of_statement, Some(err_equals_sign))),
-                                ));
-                                return Err(e);
-                            }
-                        }
-                        .output_to(start[derefs..].to_owned(), derefs)
-                        .force_output_type(Some(match parsed_type {
-                                Ok(v) => v,
-                                Err(mut e) => {
-                                    e.context.push((
-                                        format!("interpreted this as an assignment to a variable with the format <var> <var_type> = <statement>"), Some((err_start_of_statement, Some(err_equals_sign)))
-                                    ));
-                                    return Err(e);
-                                }
-                            }));
-                    }
-                    // nevermind, not var type = statement
-                    file.set_pos(file_pos_before_pot_type);
                     // parse normal statement
                     let start = start.trim();
                     match start {

mers/src/script/block.rs

@@ -1,5 +1,6 @@
 // A code block is any section of code. It contains its own local variables and functions, as well as a list of statements.
 // Types starting with S are directly parsed from Strings and unchecked. Types starting with T are type-checked templates for R-types. Types starting with R are runnable. S are converted to T after parsing is done, and T are converted to R whenever they need to run.
+// There currently are no T-Types, but we might need them in the future.
 
 use std::{
     fmt::Display,
@@ -133,7 +134,11 @@ pub mod to_runnable {
         WrongInputsForBuiltinFunction(BuiltinFunction, String, Vec<VType>),
         WrongArgsForLibFunction(String, Vec<VType>),
         ForLoopContainerHasNoInnerTypes,
-        StatementRequiresOutputTypeToBeAButItActuallyOutputsBWhichDoesNotFitInA(VType, VType, VType),
+        StatementRequiresOutputTypeToBeAButItActuallyOutputsBWhichDoesNotFitInA(
+            VType,
+            VType,
+            VType,
+        ),
     }
     impl Debug for ToRunnableError {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
@@ -658,7 +663,7 @@ pub mod to_runnable {
             if problematic_types.is_empty() {
                 statement.force_output_type = Some(force_opt.clone());
             } else {
-                return Err(ToRunnableError::StatementRequiresOutputTypeToBeAButItActuallyOutputsBWhichDoesNotFitInA(force_opt.clone(), real_output_type, VType { types: problematic_types }))
+                return Err(ToRunnableError::StatementRequiresOutputTypeToBeAButItActuallyOutputsBWhichDoesNotFitInA(force_opt.clone(), real_output_type, VType { types: problematic_types }));
             }
         }
         if let Some((opt, derefs)) = &s.output_to {
@@ -669,7 +674,11 @@ pub mod to_runnable {
                     var_derefd = if let Some(v) = var_derefd.dereference() {
                         v
                     } else {
-                        return Err(ToRunnableError::CannotDereferenceTypeNTimes(var_out.clone(), *derefs, var_derefd));
+                        return Err(ToRunnableError::CannotDereferenceTypeNTimes(
+                            var_out.clone(),
+                            *derefs,
+                            var_derefd,
+                        ));
                     }
                 }
                 let inv_types = out.fits_in(&var_derefd);
@@ -693,16 +702,19 @@ pub mod to_runnable {
                     out = if let Some(v) = out.dereference() {
                         v
                     } else {
-                        return Err(ToRunnableError::CannotDereferenceTypeNTimes(statement.out(), *derefs, out));
+                        return Err(ToRunnableError::CannotDereferenceTypeNTimes(
+                            statement.out(),
+                            *derefs,
+                            out,
+                        ));
                     }
                 }
-                linfo
+                linfo.vars.insert(opt.clone(), (ginfo.vars, out));
-                    .vars
-                    .insert(opt.clone(), (ginfo.vars, out));
                 statement.output_to = Some((ginfo.vars, *derefs));
                 ginfo.vars += 1;
             }
-        }        Ok(statement)
+        }
+        Ok(statement)
     }
 }
 

mers/src/script/builtins.rs

@@ -8,7 +8,7 @@ use crate::libs;
 
 use super::{
     block::RStatement,
-    val_data::{VData, VDataEnum, VDataThreadEnum},
+    val_data::{thread::VDataThreadEnum, VData, VDataEnum},
     val_type::{VSingleType, VType},
 };
 
@@ -236,10 +236,21 @@ impl BuiltinFunction {
             Self::Run | Self::Thread => {
                 if input.len() >= 1 {
                     input[0].types.iter().all(|v| {
+                        // all possible types of the input function must be function types
                         if let VSingleType::Function(v) = v {
-                            if v.iter().any(|(i, _)| i.len() == input.len() - 1) {
+                            // and all those functions must take as many inputs as were supplied to run() or thread() minus one (the function itself).
+                            if v.iter()
+                                .all(|(fn_in, _fn_out)| fn_in.len() == input.len() - 1)
+                            {
                                 eprintln!("Warn: Function inputs aren't type checked yet!)");
-                                // TODO!
+                                // all functions have the correct length, now check their types:
+                                // this is more difficult than it seems, because if a function covers all input types on the first and second argument, that doesn't necessarily mean that it covers all possible cases:
+                                // say out function is of type fn((int string []) (string int) []).
+                                // this covers int/string for the first two arguments, but the function actually can't handle two ints or two strings as arguments, it requires exactly one int and one string.
+                                // the most obvious implementation here would be a recursive function that goes over each type in the first argument, then calls itself recursively to check the second element and so on,
+                                // but this would likely become slower than it should for complex functions.
+                                // because of this, we just trust the programmer not to provide wrong arguments to run() and thread() for now,
+                                // until a better solution is found.
                                 true
                             } else {
                                 false

mers/src/script/val_data.rs

@@ -1,8 +1,6 @@
 use std::{
     fmt::Debug,
     sync::{Arc, Mutex},
-    thread::JoinHandle,
-    time::Duration,
 };
 
 use super::{
@@ -25,7 +23,7 @@ pub enum VDataEnum {
     Tuple(Vec<VData>),
     List(VType, Vec<VData>),
     Function(RFunction),
-    Thread(VDataThread, VType),
+    Thread(thread::VDataThread, VType),
     Reference(Arc<Mutex<VData>>),
     EnumVariant(usize, Box<VData>),
 }
@@ -157,9 +155,19 @@ impl VType {
     }
 }
 
-#[derive(Clone)]
+pub mod thread {
-pub struct VDataThread(Arc<Mutex<VDataThreadEnum>>);
+    use std::{
-impl VDataThread {
+        fmt::Debug,
+        sync::{Arc, Mutex},
+        thread::JoinHandle,
+        time::Duration,
+    };
+
+    use super::{VData, VDataEnum};
+
+    #[derive(Clone)]
+    pub struct VDataThread(Arc<Mutex<VDataThreadEnum>>);
+    impl VDataThread {
         pub fn try_get(&self) -> Option<VData> {
             match &*self.lock() {
                 VDataThreadEnum::Running(_) => None,
@@ -200,21 +208,22 @@ impl VDataThread {
             }
             mg
         }
-}
+    }
-impl Debug for VDataThread {
+    impl Debug for VDataThread {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             match &*self.lock() {
                 VDataThreadEnum::Running(_) => write!(f, "(thread running)"),
                 VDataThreadEnum::Finished(v) => write!(f, "(thread finished: {v})"),
             }
         }
-}
+    }
-pub enum VDataThreadEnum {
+    pub enum VDataThreadEnum {
         Running(JoinHandle<VData>),
         Finished(VData),
-}
+    }
-impl VDataThreadEnum {
+    impl VDataThreadEnum {
         pub fn to(self) -> VDataThread {
             VDataThread(Arc::new(Mutex::new(self)))
         }
+    }
 }

mers/src/tutor/base_comments.rs

@@ -0,0 +1,25 @@
+use crate::script::val_data::VDataEnum;
+
+use super::Tutor;
+
+pub fn run(tutor: &mut Tutor) {
+    tutor.update(Some(
+        "
+// Comments in mers start at // and end at the end of the line.
+// They also work within strings, which can be unexpected in some cases (like \"http://www...\").
+/* also works to start a comment.
+   This comment can even span multiple lines! */
+// To return to the menu, uncomment the next line:
+// true
+",
+    ));
+    loop {
+        match tutor.let_user_make_change().run(vec![]).data {
+            VDataEnum::Bool(true) => break,
+            other => {
+                tutor.set_status(format!(" - Returned {} instead of true.", other));
+                tutor.update(None);
+            }
+        }
+    }
+}

mers/src/tutor/base_return.rs

@@ -0,0 +1,38 @@
+use crate::script::val_data::VDataEnum;
+
+use super::Tutor;
+
+pub fn run(tutor: &mut Tutor) {
+    tutor.update(Some(
+        "
+// Mers doesn't have a return statement.
+// Instead, the value of the last statement is implicitly returned.
+
+// This applies to blocks:
+b = {
+    a = 10
+    a = a.add(15)
+    a
+}
+// b = 25
+
+// To functions:
+fn compute_sum(a int b int) {
+    a.add(b)
+}
+// returns a+b
+
+// and to the program itself!
+// to return to the menu, make the program return 15.
+",
+    ));
+    loop {
+        match tutor.let_user_make_change().run(vec![]).data {
+            VDataEnum::Int(15) => break,
+            other => {
+                tutor.set_status(format!(" - Returned {} instead of 15.", other));
+                tutor.update(None);
+            }
+        }
+    }
+}

mers/src/tutor/base_values.rs

@@ -0,0 +1,35 @@
+use crate::script::val_data::VDataEnum;
+
+use super::Tutor;
+
+pub fn run(tutor: &mut Tutor) {
+    tutor.update(Some("
+// Mers has the following values:
+//   bool: Either true or false
+//   int: An integer. Written 0, 1, 2, 3, -5, and so on
+//   float: A floating point number. Written 0.5, -12.378, and so on
+//   string: A piece of text. Surround something with \" and it will be a string: \"Hello, world!\"
+//   tuples: Multiple values in one place. A fixed-length collection. Surround types or statements with [] to create a tuple: [12 \"a tuple of ints and a string\" -5 -12]
+//           The empty tuple [] is often used to indicate nothing, while a 1-long tuple [v] indicates the opposite - something.
+//   list: Similar to tuples, but the closing ] is prefixed with 3 dots: [ ...]
+//         Unlike tuples, all elements in a list have the same type. Lists are resizable and can grow dynamically, while tuples cannot change their size after being created.
+//   function: A piece of code in data-form.
+//             value: anonymous_sum_function = (a int/float b int/float) a.add(b)
+//              type: fn((int int int)(int float float)(float int float)(float float float))
+//                    the reason why the type syntax is so expressive is because the function doesn't return the same type for any inputs - add will return an int if it added two ints, but will return a float when at least one argument was a float.
+//                    add will NOT return int/float, because if you know the exact input types, you also know the output type: either int and not float or float and not int.
+//   thread: Represents a different thread. The thread's return value can be retrieved by using .await(). Thread values are returned by the builtin thread() function.
+//   reference: A mutable reference to some data. Used by things like push() and remove() to avoid having to clone the entire list just to make a small change.
+//   enums: An enum can wrap any type. Enums are identified by their names and can be created using EnumName: inner_value. The type is written EnumName(InnerType).
+// return a value of type GoBackToMenu([int]) to return to the menu.
+"));
+    loop {
+        match tutor.let_user_make_change().run(vec![]).data {
+            VDataEnum::EnumVariant(..) => break,
+            other => {
+                tutor.set_status(format!(" - Returned {other} instead of an enum."));
+                tutor.update(None);
+            }
+        }
+    }
+}

mers/src/tutor/menu.rs

@@ -0,0 +1,39 @@
+use crate::script::val_data::VDataEnum;
+
+use super::Tutor;
+
+pub const MAX_POS: usize = 3;
+
+pub fn run(mut tutor: Tutor) {
+    loop {
+        tutor.current_pos = 0;
+        tutor.update(Some(
+            "
+// Welcome to the mers tutor!
+// This is the main menu. Change the number to navigate to a specific part.
+0
+//   1  Comments
+//   2  Values
+//   3  Returns
+",
+        ));
+        loop {
+            match tutor.let_user_make_change().run(vec![]).data {
+                VDataEnum::Int(pos) => {
+                    tutor.current_pos = (pos.max(0) as usize).min(MAX_POS);
+                    match tutor.current_pos {
+                        0 => continue,
+                        1 => super::base_comments::run(&mut tutor),
+                        2 => super::base_values::run(&mut tutor),
+                        3 => super::base_return::run(&mut tutor),
+                        _ => unreachable!(),
+                    }
+                }
+                other => {
+                    tutor.set_status(format!(" - Returned {} instead of an integer", other));
+                }
+            }
+            break;
+        }
+    }
+}

mers/src/tutor/mod.rs

@@ -0,0 +1,112 @@
+use std::{path::PathBuf, thread::JoinHandle, time::Instant};
+
+use crate::{
+    parse::{self, parse::ScriptError},
+    script::{block::RScript, val_data::VDataEnum},
+};
+
+mod base_comments;
+mod base_return;
+mod base_values;
+mod menu;
+
+pub fn start(spawn_new_terminal_for_editor: bool) {
+    let (sender, receiver) = std::sync::mpsc::channel();
+    let (editor_join_handle, file_path) = crate::interactive_mode::fs_watcher::main(
+        spawn_new_terminal_for_editor,
+        "// Welcome to the mers tutor!
+
+// This is an interactive experience. After making a change to this file,
+// save and then reload it to see the tutor's updates.
+// To begin, change the following value from false to true:
+
+false
+",
+        Box::new(move |file| {
+            let mut file =
+                parse::file::File::new(std::fs::read_to_string(file).unwrap(), PathBuf::new());
+            sender.send(parse::parse::parse(&mut file)).unwrap();
+        }),
+    )
+    .unwrap();
+    let mut tutor = Tutor {
+        current_pos: 0,
+        current_status: String::new(),
+        written_status_byte_len: 0,
+        editor_join_handle,
+        file_path,
+        receiver,
+    };
+    loop {
+        if let VDataEnum::Bool(true) = tutor.let_user_make_change().run(vec![]).data {
+            break;
+        }
+    }
+    menu::run(tutor);
+}
+
+use menu::MAX_POS;
+
+pub struct Tutor {
+    current_pos: usize,
+    current_status: String,
+    written_status_byte_len: usize,
+    editor_join_handle: JoinHandle<()>,
+    file_path: PathBuf,
+    receiver: std::sync::mpsc::Receiver<Result<RScript, ScriptError>>,
+}
+impl Tutor {
+    /// only returns after a successful compile. before returning, does not call self.update() - you have to do that manually.
+    pub fn let_user_make_change(&mut self) -> RScript {
+        // eprintln!(" - - - - - - - - - - - - - - - - - - - - - - - - -");
+        let script = loop {
+            match self.receiver.recv().unwrap() {
+                Err(e) => {
+                    self.current_status = format!(
+                        " - Error during build{}",
+                        e.to_string()
+                            .lines()
+                            .map(|v| format!("\n// {v}"))
+                            .collect::<String>()
+                    )
+                }
+                Ok(script) => {
+                    break script;
+                }
+            }
+            self.update(None);
+        };
+        self.current_status = format!(" - OK");
+        script
+    }
+    pub fn set_status(&mut self, new_status: String) {
+        self.current_status = new_status;
+    }
+    pub fn update(&mut self, overwrite_contents_with: Option<&str>) {
+        if self.editor_join_handle.is_finished() {
+            eprintln!("Error has closed!");
+            std::process::exit(0);
+        }
+        let string = std::fs::read_to_string(self.file_path()).unwrap();
+        let status = format!(
+            "// Tutor: {}/{MAX_POS}{}\n",
+            self.current_pos, self.current_status,
+        );
+        let status_len = status.len();
+        std::fs::write(
+            self.file_path(),
+            if let Some(new_content) = overwrite_contents_with {
+                status + new_content
+            } else {
+                status + &string[self.written_status_byte_len..]
+            },
+        )
+        .unwrap();
+        self.written_status_byte_len = status_len;
+        // ignore this update to the file
+        _ = self.receiver.recv().unwrap();
+    }
+    pub fn file_path(&self) -> &PathBuf {
+        &self.file_path
+    }
+}

mers_libs/gui_v1/src/main.rs

@@ -9,13 +9,8 @@ use iced::{
     widget::{button, column, row, text},
     Application, Command, Element, Renderer, Settings, Subscription, Theme,
 };
-use mers::{
+
-    libs::inlib::{MyLib, MyLibTask},
+use mers_libs::{MyLib, MyLibTask, VData, VDataEnum, VSingleType, VType};
-    script::{
-        val_data::{VData, VDataEnum},
-        val_type::{VSingleType, VType},
-    },
-};
 
 /*
 
@@ -264,7 +259,6 @@ impl Application for App {
         format!("{}", self.title)
     }
     fn update(&mut self, message: Self::Message) -> Command<Self::Message> {
-        let mut commands = vec![];
         match message {
             Message::Tick => {
                 let mut changed_layout = false;
@@ -303,7 +297,7 @@ impl Application for App {
                 ))
                 .unwrap(),
         }
-        Command::batch(commands)
+        Command::none()
     }
     fn subscription(&self) -> Subscription<Message> {
         time::every(Duration::from_millis(10)).map(|_| Message::Tick)

mers_libs/http_requests_v1/src/main.rs

@@ -1,10 +1,4 @@
-use mers::{
+use mers_libs::{MyLib, MyLibTask, VDataEnum, VSingleType, VType};
-    libs::inlib::{MyLib, MyLibTask},
-    script::{
-        val_data::VDataEnum,
-        val_type::{VSingleType, VType},
-    },
-};
 
 fn main() {
     let (mut my_lib, mut run) = MyLib::new(