readme and examples n stuff

README.org

@@ -1,5 +1,5 @@
 * effers
-effect handlers in rust
+ergonomic effect handlers in rust
 
 ** how to use
 *** defining effects
@@ -7,24 +7,30 @@ effects are defined with traits
 
 #+begin_src rust
 trait Printer {
-    fn print(&mut self, s: &str);
+    fn print(&self, s: &str);
+    fn available() -> bool;
 }
 trait Logger {
     fn debug(&mut self, s: &str);
-    fn info(&mut self, s: &str);
+    fn info(self, s: &str);
 }
 #+end_src
 
-all the trait functions (that are used in programs) must take ~&mut self~ as a parameter
+functions can take ~self~, ~&self~, ~&mut self~, or no ~self~ parameter. at this point ~self~ parameters with a specified type (like ~self: Box<Self>~) are not supported
 
 *** defining a program
 
-programs are defined as a normal function, with the added ~program~ attribute
+programs are defined as a normal function, with the added ~program~ attribute, which specifies (optional) a name for the program, and (required) the list of effects and corresponding functions that are used
 
 #+begin_src rust
-#[program(Smth => Printer(print as p), Logger(debug, info))]
+#[effers::program(MyCoolProgram =>
-fn smth(val: u8) -> u8 {
+    Printer(print(&self) as p, available as printer_available),
+    Logger(debug(&mut self), info(self))
+)]
+fn my_program(val: u8) -> u8 {
+    if printer_available() {
         p("hey hi hello");
+    }
 
     debug("this is a debug-level log");
     info("this is a info-level log");
@@ -33,22 +39,47 @@ fn smth(val: u8) -> u8 {
 }
 #+end_src
 
-the first token (~Smth~) will be the name of the program. effects are listed after the ~=>~ token
+**** name
+
+the first token (~MyCoolProgram~) will be the name of the program. this is optional, and can be skipped:
+
+#+begin_src rust
+#[program(
+    Printer(print(&self) as p, available as printer_available),
+    Logger(debug(&mut self), info(self))
+)]
+#+end_src
+
+if skipped, the default name will be the program function's name (~my_program~) in PascalCase (~MyProgram~)
 
 **** listing effects
 effects are listed by writing the trait's name, followed by a parenthesized list of the functions that will be used
 
-functions can be given an alias using the ~as~ keyword
+***** listing effect functions
+
+due to limitations of proc-macros, it's unknown what kind of ~self~ parameter the function takes, if any, and so it has to be explicitly specified (if you have ideas on how to fix this, please open a PR!): here's how each type is specified:
+
+- ~fn print();~: ~print~
+- ~fn print(self);~: ~print(self)~
+- ~fn print(mut self);~: ~print(self)~
+- ~fn print(&self);~: ~print(&self)~
+- ~fn print(&mut self);~: ~print(&mut self)~
+
+***** effect function aliases
+functions can be given an alias using the ~as~ keyword (~print(&self) as p~) so that the function can be called by a different name inside the program
 
 *** defining effect handlers
-effect handlers are defined by declaring a struct, and implementing the trait on it
+effect handlers are defined by declaring a struct, and implementing the corresponding trait on it
 
 #+begin_src rust
 struct IoPrinter;
 impl Printer for IoPrinter {
-    fn print(&mut self, s: &str) {
+    fn print(&self, s: &str) {
         println!("{}", s)
     }
+    fn available() -> bool {
+        true
+    }
 }
 
 struct FileLogger;
@@ -56,88 +87,21 @@ impl Logger for FileLogger {
     fn debug(&mut self, s: &str) {
         println!("debug: {}", s)
     }
-    fn info(&mut self, s: &str) {
+    fn info(self, s: &str) {
         println!("info: {}", s)
     }
 }
 #+end_src
 
 *** running programs
-programs are run by providing the corresponding handlers in order, and finally calling the ~run~ method, providing it the required parameters
+programs are run by providing the corresponding handlers *in the order listed in the program definition*, and finally calling the ~run~ method, providing it the required parameters
 
 #+begin_src rust
-let result: u8 = Smth.add(IoPrinter).add(FileLogger).run(3);
+let result: u8 = MyCoolProgram.add(IoPrinter).add(FileLogger).run(3);
 assert_eq!(result, 6);
 #+end_src
 
-** full example
+** examples
-#+begin_src rust
+- [[./examples/main.rs][main: general use case]]
-use effers::program;
+- [[./examples/clone.rs][clone: how cloning and copying programs works]]
-
+- [[./examples/module.rs][module: effects from other modules are supported]]
-#[program(Smth => Printer(print as p), Logger(debug, info))]
-fn smth(val: u8) -> u8 {
-    p("hey hi hello");
-
-    debug("this is a debug-level log");
-    info("this is a info-level log");
-
-    val + 3
-}
-
-fn main() {
-    // maybe smth like this?
-    let result: u8 = Smth.add(IoPrinter).add(FileLogger).run(3);
-    assert_eq!(result, 6);
-    let other_result: u8 = Smth
-        .add(IoPrinter)
-        .add(NetworkLogger {
-            credentials: "secret password".to_string(),
-        })
-        .run(8);
-    assert_eq!(other_result, 11);
-}
-
-// effects
-trait Printer {
-    fn print(&mut self, s: &str);
-}
-trait Logger {
-    fn debug(&mut self, s: &str);
-    fn info(&mut self, s: &str);
-}
-
-struct IoPrinter;
-impl Printer for IoPrinter {
-    fn print(&mut self, s: &str) {
-        println!("{}", s)
-    }
-}
-
-struct FileLogger;
-impl Logger for FileLogger {
-    fn debug(&mut self, s: &str) {
-        println!("debug: {}", s)
-    }
-    fn info(&mut self, s: &str) {
-        println!("info: {}", s)
-    }
-}
-
-struct NetworkLogger {
-    credentials: String,
-}
-impl Logger for NetworkLogger {
-    fn debug(&mut self, s: &str) {
-        println!(
-            "debug through network: {}; with password {}",
-            s, self.credentials
-        )
-    }
-    fn info(&mut self, s: &str) {
-        println!(
-            "info through network: {}; with password {}",
-            s, self.credentials
-        )
-    }
-}
-#+end_src

effers-derive/Cargo.toml

@@ -10,3 +10,4 @@ proc-macro = true
 syn = {version = "1.0", features = ["full", "extra-traits", "visit-mut"]}
 quote = "1.0"
 proc-macro2 = "1.0"
+convert_case = "0.5.0"

effers-derive/src/intermediate_structs.rs

@@ -0,0 +1,82 @@
+use proc_macro2::{Span, TokenStream};
+use quote::quote;
+use syn::{Ident, Path};
+
+use crate::{lette::LettersIter, Args};
+
+pub struct IntermediateStruct {
+    pub tokens: TokenStream,
+    pub id: Ident,
+    pub traits: Vec<Path>,
+    pub letters: Vec<Ident>,
+    pub generics: TokenStream,
+}
+
+impl IntermediateStruct {
+    pub fn new(
+        tokens: TokenStream,
+        id: Ident,
+        traits: Vec<Path>,
+        letters: Vec<Ident>,
+        generics: TokenStream,
+    ) -> Self {
+        Self {
+            tokens,
+            id,
+            traits,
+            letters,
+            generics,
+        }
+    }
+}
+
+pub fn intermediate_structs(args: &Args, prog_name: &Ident) -> Vec<IntermediateStruct> {
+    let struct_with = format!("{}With", prog_name);
+    args.effects
+        .iter()
+        .fold(
+            (vec![], struct_with, vec![]),
+            |(mut structs, name, mut traits), eff| {
+                let name = format!("{}{}", &name, &eff.name);
+
+                traits.push(eff.path.clone());
+
+                // kinda messy
+                let letters = LettersIter::new()
+                    .take(traits.len())
+                    .map(|c| Ident::new(&c.to_string(), Span::call_site()));
+                let generics = traits
+                    .iter()
+                    .zip(letters.clone())
+                    .map(|(t, c)| quote!(#c: #t,))
+                    .collect::<TokenStream>();
+
+                let id = Ident::new(&name, Span::call_site());
+                let last = if let Some(&IntermediateStruct {
+                    ref id,
+                    ref letters,
+                    ..
+                }) = &structs.last()
+                {
+                    let gen = letters.iter().map(|l| quote!(#l,)).collect::<TokenStream>();
+                    quote!(#id<#gen>)
+                } else {
+                    quote!(#prog_name)
+                };
+                let last_letter = letters.clone().last();
+                structs.push(IntermediateStruct::new(
+                    quote! {
+                        #[derive(Clone, Copy)]
+                        struct #id<#generics>(#last, #last_letter);
+                    },
+                    id,
+                    traits.clone(),
+                    letters.collect::<Vec<_>>(),
+                    generics,
+                ));
+
+                (structs, name, traits)
+            },
+        )
+        .0
+}

effers-derive/src/lette.rs

@@ -0,0 +1,40 @@
+const LETTERS: &'static str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+#[derive(Clone, Copy)]
+pub struct LettersIter {
+    idx: usize,
+}
+
+impl LettersIter {
+    pub fn new() -> Self {
+        Self { idx: 0 }
+    }
+}
+impl Iterator for LettersIter {
+    type Item = String;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let l = LETTERS.chars().nth(self.idx % LETTERS.len()).unwrap();
+        let c = self.idx / LETTERS.len();
+
+        self.idx += 1;
+
+        Some(l.to_string().repeat(c + 1))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn iter() {
+        let mut i = LettersIter::new();
+
+        assert_eq!(i.next(), Some("A".to_string()));
+        assert_eq!(i.next(), Some("B".to_string()));
+        assert_eq!(i.nth(23), Some("Z".to_string()));
+        assert_eq!(i.next(), Some("AA".to_string()));
+        assert_eq!(i.next(), Some("BB".to_string()));
+    }
+}

effers-derive/src/lib.rs

@@ -1,24 +1,31 @@
+use convert_case::{Case, Casing};
+use lette::LettersIter;
 use proc_macro2::{Span, TokenStream};
 use quote::quote;
-use syn::parse::{Parse, ParseStream, Result};
+use syn::token::{Dot, Mut, SelfValue};
-use syn::punctuated::Punctuated;
-use syn::token::{Mut, SelfValue};
 use syn::visit_mut::VisitMut;
 use syn::{
-    parse_macro_input, Expr, ExprCall, FnArg, Ident, ItemFn, Path, PathSegment, Receiver, Token,
+    parse_macro_input, Expr, ExprCall, ExprField, FnArg, Ident, Index, ItemFn, Member, PathSegment,
-    Type,
+    QSelf, Receiver,
 };
 
+mod parse;
+use parse::Args;
+mod intermediate_structs;
+mod lette;
+use intermediate_structs::*;
+
 #[proc_macro_attribute]
 pub fn program(
     attr: proc_macro::TokenStream,
     item: proc_macro::TokenStream,
 ) -> proc_macro::TokenStream {
     let item = parse_macro_input!(item as syn::ItemFn);
+    // dbg!(&item);
     let mut args = parse_macro_input!(attr as Args);
 
     if args.name.is_none() {
-        let i = first_letter_to_uppper_case(item.sig.ident.to_string());
+        let i = item.sig.ident.to_string().to_case(Case::Pascal);
         args.name = Some(Ident::new(&i, Span::call_site()));
     }
 
@@ -31,122 +38,6 @@ pub fn program(
     proc_macro::TokenStream::from(out)
 }
 
-fn first_letter_to_uppper_case(s1: String) -> String {
-    let mut c = s1.chars();
-    match c.next() {
-        None => String::new(),
-        Some(f) => f.to_uppercase().collect::<String>() + c.as_str(),
-    }
-}
-
-#[derive(Debug)]
-struct Args {
-    name: Option<Ident>,
-    effects: Vec<Effect>,
-}
-
-#[derive(Debug)]
-struct Effect {
-    name: Ident,
-    path: Path,
-    functions: Vec<EffectFunction>,
-}
-
-#[derive(Debug)]
-struct EffectFunction {
-    ident: Ident,
-    alias: Option<Ident>,
-}
-
-fn get_name_from_args(input: &mut ParseStream) -> Result<Ident> {
-    let name: Ident = input.parse()?;
-    input.parse::<Token![=>]>()?;
-    Ok(name)
-}
-impl Parse for Args {
-    fn parse(mut input: ParseStream) -> Result<Self> {
-        let name = get_name_from_args(&mut input).ok();
-
-        let effects: Vec<_> = Punctuated::<ExprCall, Token![,]>::parse_terminated(input)?
-            .into_iter()
-            .collect();
-
-        let effects: Vec<Effect> = effects
-            .into_iter()
-            .flat_map(|e| {
-                Some(Effect {
-                    name: name_from_expr_call(&e)?,
-                    path: if let Expr::Path(p) = &*e.func {
-                        Some(p.path.clone())
-                    } else {
-                        None
-                    }?,
-                    functions: effects_from_expr_call(&e),
-                })
-            })
-            .collect();
-
-        Ok(Args { name, effects })
-    }
-}
-
-fn name_from_expr_call(e: &ExprCall) -> Option<Ident> {
-    if let Expr::Path(e) = &*e.func {
-        Some(e.path.get_ident()?.clone())
-    } else {
-        None
-    }
-}
-
-/// returns the list of functions, with their optional alias
-fn effects_from_expr_call(e: &ExprCall) -> Vec<EffectFunction> {
-    e.args
-        .iter()
-        .cloned()
-        .flat_map(|p| match p {
-            Expr::Path(e) => Some(EffectFunction {
-                ident: e.path.get_ident().unwrap().clone(), // TODO remove this unwrap
-                alias: None,
-            }),
-            Expr::Cast(cast) => match (*cast.expr, *cast.ty) {
-                (Expr::Path(expr), Type::Path(ty)) => Some(EffectFunction {
-                    ident: expr.path.get_ident().unwrap().clone(),
-                    alias: Some(ty.path.get_ident()?.clone()),
-                }),
-                _ => None,
-            },
-            _ => None,
-        })
-        .collect()
-}
-
-#[derive(Clone, Copy)]
-struct LettersIter {
-    idx: u32,
-}
-
-impl LettersIter {
-    fn new() -> Self {
-        Self {
-            idx: 'A' as u32 - 1,
-        }
-    }
-}
-impl Iterator for LettersIter {
-    type Item = char;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        for _ in 0..100 {
-            self.idx += 1;
-            if let Some(c) = char::from_u32(self.idx) {
-                return Some(c);
-            }
-        }
-
-        None
-    }
-}
-
 /// takes in the function contents, and returns the structs n stuff
 fn rewrite_item_into_struct(func: ItemFn, args: Args) -> TokenStream {
     let prog_name = (&args.name).clone().unwrap();
@@ -166,6 +57,7 @@ fn rewrite_item_into_struct(func: ItemFn, args: Args) -> TokenStream {
     let final_impl = final_impl(intermediate_structs.last().unwrap(), func, &args);
 
     let out = quote! {
+        #[derive(Clone, Copy)]
         struct #prog_name;
 
         #inters_tokens
@@ -177,82 +69,6 @@ fn rewrite_item_into_struct(func: ItemFn, args: Args) -> TokenStream {
     TokenStream::from(out)
 }
 
-struct IntermediateStruct {
-    tokens: TokenStream,
-    id: Ident,
-    traits: Vec<Ident>,
-    letters: Vec<Ident>,
-    generics: TokenStream,
-}
-
-impl IntermediateStruct {
-    fn new(
-        tokens: TokenStream,
-        id: Ident,
-        traits: Vec<Ident>,
-        letters: Vec<Ident>,
-        generics: TokenStream,
-    ) -> Self {
-        Self {
-            tokens,
-            id,
-            traits,
-            letters,
-            generics,
-        }
-    }
-}
-
-fn intermediate_structs(args: &Args, prog_name: &Ident) -> Vec<IntermediateStruct> {
-    let struct_with = format!("{}With", prog_name);
-    args.effects
-        .iter()
-        .fold(
-            (vec![], struct_with, vec![]),
-            |(mut structs, name, mut traits), eff| {
-                let name = format!("{}{}", &name, &eff.name);
-
-                traits.push(eff.name.clone());
-
-                // kinda messy
-                let letters = LettersIter::new()
-                    .take(traits.len())
-                    .map(|c| Ident::new(&c.to_string(), Span::call_site()));
-                let generics = traits
-                    .iter()
-                    .zip(letters.clone())
-                    .map(|(t, c)| quote!(#c: #t,))
-                    .collect::<TokenStream>();
-
-                let id = Ident::new(&name, Span::call_site());
-                let last = if let Some(&IntermediateStruct {
-                    ref id,
-                    ref letters,
-                    ..
-                }) = &structs.last()
-                {
-                    let gen = letters.iter().map(|l| quote!(#l,)).collect::<TokenStream>();
-                    quote!(#id<#gen>)
-                } else {
-                    quote!(#prog_name)
-                };
-                let last_letter = letters.clone().last();
-                structs.push(IntermediateStruct::new(
-                    quote! {
-                        struct #id<#generics>(#last, #last_letter);
-                    },
-                    id,
-                    traits.clone(),
-                    letters.collect::<Vec<_>>(),
-                    generics,
-                ));
-
-                (structs, name, traits)
-            },
-        )
-        .0
-}
-
 fn impls(prog_name: &Ident, intermediate_structs: &Vec<IntermediateStruct>) -> TokenStream {
     let mut impls = vec![];
     let mut id = quote!(#prog_name);
@@ -342,7 +158,7 @@ impl<'a> syn::visit_mut::VisitMut for FuncRewriter<'a> {
         // check if the function name is in args
         // if it is, replace it with the correct name
         if let Expr::Path(path) = &mut *node.func {
-            for (i, effect) in self.args.effects.iter().enumerate() {
+            for ((i, effect), l) in self.args.effects.iter().enumerate().zip(LettersIter::new()) {
                 for func in &effect.functions {
                     let ident = func.alias.clone().unwrap_or(func.ident.clone());
                     if path.path.is_ident(&ident) {
@@ -353,17 +169,61 @@ impl<'a> syn::visit_mut::VisitMut for FuncRewriter<'a> {
                             arguments: syn::PathArguments::None,
                         });
 
+                        let span = [Span::call_site()];
+
                         path.path = effect_path;
 
+                        // qualify the trait se we get
+                        // <A as Printer>::print
+                        // instead of Printer::print
+                        let ty: syn::Type = syn::parse_str(&l).unwrap();
+                        path.qself = Some(QSelf {
+                            lt_token: syn::token::Lt {
+                                spans: span.clone(),
+                            },
+                            ty: Box::new(ty),
+                            position: path.path.segments.len() - 1,
+                            as_token: Some(syn::token::As { span: span[0] }),
+                            gt_token: syn::token::Gt { spans: span },
+                        });
+
+                        // if the effect function takes a self, add it to the list of params
+                        if let Some(mut expr) = func.self_reference.clone() {
                             // then change the parameters so the handler is the first
                             // get the effect's index, and add the inverse num of `.0`s
                             let idx = eff_len - (i + 1);
-                        let s = format!("&mut self{}.1", ".0".repeat(idx));
+
-                        let expr: Expr = syn::parse_str(&s).unwrap();
+                            for _ in 0..idx {
+                                expr = Expr::Field(ExprField {
+                                    attrs: vec![],
+                                    base: Box::new(expr),
+                                    dot_token: Dot {
+                                        spans: [Span::call_site()],
+                                    },
+                                    member: Member::Unnamed(Index {
+                                        index: 0,
+                                        span: Span::call_site(),
+                                    }),
+                                });
+                            }
+
+                            expr = Expr::Field(ExprField {
+                                attrs: vec![],
+                                base: Box::new(expr),
+                                dot_token: Dot {
+                                    spans: [Span::call_site()],
+                                },
+                                member: Member::Unnamed(Index {
+                                    index: 1,
+                                    span: Span::call_site(),
+                                }),
+                            });
+
                             node.args.insert(0, expr);
                         }
                     }
                 }
             }
         }
+    }
 }

effers-derive/src/parse.rs

@@ -0,0 +1,107 @@
+use syn::parse::{Parse, ParseStream, Result};
+use syn::punctuated::Punctuated;
+use syn::token::Paren;
+use syn::{parenthesized, Expr, ExprPath, ExprReference, Ident, Path, Token};
+
+#[derive(Debug)]
+pub struct Args {
+    pub name: Option<Ident>,
+    pub effects: Vec<Effect>,
+}
+
+#[derive(Debug)]
+pub struct Effect {
+    pub name: Ident,
+    pub path: Path,
+    pub paren: Paren,
+    pub functions: Vec<EffectFunction>,
+}
+
+#[derive(Debug)]
+pub struct EffectFunction {
+    pub ident: Ident,
+    pub alias: Option<Ident>,
+    pub self_reference: Option<Expr>,
+}
+
+impl Parse for Args {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let name = if input.peek2(Token!(=>)) {
+            let name: Ident = input.parse()?;
+            input.parse::<Token![=>]>()?;
+            Some(name)
+        } else {
+            None
+        };
+
+        let effects: Vec<Effect> = Punctuated::<Effect, Token![,]>::parse_terminated(input)?
+            .into_iter()
+            .collect();
+
+        Ok(Args { name, effects })
+    }
+}
+
+impl Parse for Effect {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let path: Path = input.parse()?;
+        let content;
+        let paren = parenthesized!(content in input);
+        let functions = Punctuated::<EffectFunction, Token![,]>::parse_terminated(&content)?
+            .into_iter()
+            .collect();
+
+        let name = (&path)
+            .segments
+            .last()
+            .expect("There must be at least one PathSegment")
+            .ident
+            .clone();
+
+        Ok(Effect {
+            name,
+            path,
+            functions,
+            paren,
+        })
+    }
+}
+impl Parse for EffectFunction {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let ident = input.parse()?;
+
+        let self_reference: Option<Expr> = if input.peek(Paren) {
+            let content;
+            parenthesized!(content in input);
+
+            // &mut self
+            if content.peek(Token![&]) && content.peek2(Token![mut]) && content.peek3(Token![self])
+            {
+                Some(Expr::Reference(content.parse::<ExprReference>()?))
+            } else
+            // &self
+            if content.peek(Token![&]) && content.peek2(Token![self]) {
+                Some(Expr::Reference(content.parse::<ExprReference>()?))
+            } else if content.peek(Token![self]) {
+                Some(Expr::Path(content.parse::<ExprPath>()?))
+            } else {
+                None
+            }
+        } else {
+            None
+        };
+
+        let alias: Option<Ident> = if input.peek(Token![as]) {
+            input.parse::<Token![as]>()?;
+            input.parse()?
+        } else {
+            None
+        };
+
+        Ok(EffectFunction {
+            ident,
+            alias,
+            self_reference,
+        })
+    }
+}

examples/clone.rs

@@ -0,0 +1,71 @@
+use effers::program;
+
+#[program(Incrementer(increment(&self)), Printer(print(&self)))]
+fn prog(val: u8) -> u8 {
+    let x = increment(val);
+    let y = increment(x);
+
+    print(x);
+
+    x + y
+}
+
+pub trait Incrementer {
+    fn increment(&self, v: u8) -> u8;
+}
+
+#[derive(Clone, Copy)]
+pub struct TestInc;
+impl Incrementer for TestInc {
+    fn increment(&self, v: u8) -> u8 {
+        v + 3
+    }
+}
+
+trait Printer {
+    fn print(&self, s: u8);
+}
+
+#[derive(Clone, Copy)]
+struct Printer1;
+impl Printer for Printer1 {
+    fn print(&self, s: u8) {
+        println!("1: {}", s)
+    }
+}
+#[derive(Clone)]
+struct Printer2 {
+    prefix: String,
+}
+impl Printer for Printer2 {
+    fn print(&self, s: u8) {
+        println!("2: {} {}", self.prefix, s)
+    }
+}
+
+fn main() {
+    // if a program only has Clone effects, the program also becomes clone
+    // same applies for Copy
+
+    // a is Copy since TestInc is Copy
+    let a = Prog.add(TestInc);
+
+    let b = a.add(Printer1);
+    let c = a.add(Printer2 {
+        prefix: "this is a number".to_string(),
+    });
+
+    // both TestInc and Printer1 are Copy,
+    // therefore b is copy, and we can call it as much as we want
+    let first_result = b.run(0);
+    assert_eq!(first_result, 9);
+    let second_result = b.run(2);
+    assert_eq!(second_result, 13);
+
+    // since Printer2 is not Copy, but it is Clone,
+    // c is Clone but not Copy
+    let first_result = c.clone().run(0);
+    assert_eq!(first_result, 9);
+    let second_result = c.run(2);
+    assert_eq!(second_result, 13);
+}

examples/main.rs

@@ -1,8 +1,13 @@
 use effers::program;
 
-#[program(Smth => Printer(print as p), Logger(debug, info))]
+#[program(MyCoolProgram =>
-fn smth(val: u8) -> u8 {
+    Printer(print(&self) as p, available as printer_available),
+    Logger(debug(&mut self), info(self))
+)]
+fn my_program(val: u8) -> u8 {
+    if printer_available() {
         p("hey hi hello");
+    }
 
     debug("this is a debug-level log");
     info("this is a info-level log");
@@ -10,32 +15,44 @@ fn smth(val: u8) -> u8 {
     val + 3
 }
 
+#[program(Printer(print(&self) as p))]
+fn other_program() {
+    p("hey hi hello");
+}
+
 fn main() {
-    // maybe smth like this?
+    // call the first program twice
-    let result: u8 = Smth.add(IoPrinter).add(FileLogger).run(3);
+    let result: u8 = MyCoolProgram.add(IoPrinter).add(FileLogger).run(3);
     assert_eq!(result, 6);
-    let other_result: u8 = Smth
+    let other_result: u8 = MyCoolProgram
         .add(IoPrinter)
         .add(NetworkLogger {
             credentials: "secret password".to_string(),
         })
         .run(8);
     assert_eq!(other_result, 11);
+
+    // other program
+    OtherProgram.add(IoPrinter).run();
 }
 
 trait Printer {
-    fn print(&mut self, s: &str);
+    fn print(&self, s: &str);
+    fn available() -> bool;
 }
 trait Logger {
     fn debug(&mut self, s: &str);
-    fn info(&mut self, s: &str);
+    fn info(self, s: &str);
 }
 
 struct IoPrinter;
 impl Printer for IoPrinter {
-    fn print(&mut self, s: &str) {
+    fn print(&self, s: &str) {
         println!("{}", s)
     }
+    fn available() -> bool {
+        true
+    }
 }
 
 struct FileLogger;
@@ -43,7 +60,7 @@ impl Logger for FileLogger {
     fn debug(&mut self, s: &str) {
         println!("debug: {}", s)
     }
-    fn info(&mut self, s: &str) {
+    fn info(self, s: &str) {
         println!("info: {}", s)
     }
 }
@@ -58,7 +75,7 @@ impl Logger for NetworkLogger {
             s, self.credentials
         )
     }
-    fn info(&mut self, s: &str) {
+    fn info(self, s: &str) {
         println!(
             "info through network: {}; with password {}",
             s, self.credentials

examples/module.rs

@@ -0,0 +1,24 @@
+// Effects can be referenced from inside a module
+#[effers::program(inc::Incrementer(increment(&self)))]
+fn prog(val: u8) -> u8 {
+    let x = increment(val);
+    let y = increment(x);
+    x + y
+}
+
+mod inc {
+    pub trait Incrementer {
+        fn increment(&self, v: u8) -> u8;
+    }
+
+    pub struct TestInc;
+    impl Incrementer for TestInc {
+        fn increment(&self, v: u8) -> u8 {
+            v + 3
+        }
+    }
+}
+
+fn main() {
+    Prog.add(inc::TestInc).run(1);
+}

src/lib.rs

@@ -4,21 +4,37 @@ pub use effers_derive::program;
 mod test {
     use super::*;
 
-    #[program(Smth => Printer(print as p), Logger(debug, info))]
+    #[program(Smth => Printer(print(&self) as p), Logger(debug(self), info(&mut self)), inc::Incrementer(increment))]
     fn smth(val: u8) -> u8 {
-        p("hey hi hello");
+        let s = p("hey hi hello");
 
-        debug("this is a debug-level log");
         info("this is a info-level log");
+        debug("this is a debug-level log");
 
-        val + 3
+        let _s = p("hey hi hello");
+
+        dbg!(s);
+
+        let x = increment(val);
+        let y = increment(x);
+        x + y
     }
 
     trait Printer {
-        fn print(&mut self, s: &str);
+        fn print(&self, s: &str) -> &str;
     }
     trait Logger {
-        fn debug(&mut self, s: &str);
+        fn debug(self, s: &str);
         fn info(&mut self, s: &str);
     }
+    mod inc {
+        pub trait Incrementer {
+            fn increment(v: u8) -> u8;
+        }
+    }
+
+    #[program(Printer(print(&self) as p))]
+    fn ohter() {
+        let _s = p("hey hi hello");
+    }
 }