Fully fledged lambdas, along with efficiency tweaks across the ast

Readme.org

@@ -152,7 +152,34 @@ CURRENT VALUE AND/OR BODY:
 #+END_SRC
 
 *** TODO Quote and Eval
-*** TODO Lambda
+*** Lambda
+Another form of homoiconicity is the *anonymous function*.
+This is a nameless function being passed around as data.
+It can be bound to a variable, or called directly.
+An *anonymous function* is created with the ~lambda~ function.
+
+Here is an example of a lambda function:
+#+BEGIN_SRC lisp
+  (lambda (x y) (add x y))
+  ;;       |     ^ this is the function body
+  ;;       +-> this is the argument list
+#+END_SRC
+
+The result of the lambda call is returned as a piece of data.
+It can later be called inline or bound to a variable.
+
+Here is an example of an inline lambda call:
+#+BEGIN_SRC lisp
+  ((lambda (x y) (add x y)) 1 2)
+#+END_SRC
+This call returns ~3~.
+
+Here is the lambda bound to a variable inside a let statement:
+#+BEGIN_SRC lisp
+  (let ((adder (lambda (x y) (add x y)))) ;; let form contains one local var
+            (adder 1 2))                  ;; local var (lambda) called here
+#+END_SRC
+
 *** TODO Defining variables and functions
 **** TODO Anatomy
 **** TODO Naming conventions
@@ -322,21 +349,6 @@ This contains any executable target of this project. Notably the main shell file
 Note: this section will not show the status of each item unless you are viewing it with a proper orgmode viewer.
 Note: this section only tracks the state of incomplete TODO items. Having everything on here would be cluttered.
 
-*** TODO Lambda
-IMPLEMENTATION:
-  - [-] implement a new Ctr type to encapsulate function and args
-  - [ ] need a new case in store for when bound to a var
-        (honestly store should be rewritten)
-  - [ ] need a case in eval that mirrors the function call case
-
-DOCUMENTATION:
-- [ ] let case for creating and applying a lambda
-
-TEST:
-- [ ] lambda to_string input equivalency
-- [ ] (eq? ((lambda (x y) (add x y)) 1 2) (add 1 2))
-- [ ] let case for creating and applying a lambda
-
 *** TODO list contains via circuit
 *** TODO Map function
 - DOCUMENTATION + TEST:

src/eval.rs

@@ -16,13 +16,14 @@
  */
 
 use crate::segment::{Ctr, Seg};
-use crate::sym::SymTable;
+use crate::sym::{SymTable, call_lambda};
 
 /* iterates over a syntax tree
  * returns a NEW LIST of values
  * representing the simplest possible form of the input
  */
 pub fn eval(ast: &Seg, syms: &mut SymTable) -> Result<Box<Ctr>, String> {
+    println!("E: {}", ast);
     // data to return
     let mut ret = Box::from(Ctr::None);
     let mut first = true;
@@ -39,7 +40,17 @@ pub fn eval(ast: &Seg, syms: &mut SymTable) -> Result<Box<Ctr>, String> {
     let mut none = false;
     while !none {
         match &**arg_car {
-            Ctr::Seg(ref inner) => car = eval(inner, syms)?,
+            Ctr::Seg(ref inner) => {
+                let interm = eval(inner, syms)?;
+                if let Ctr::Lambda(ref l) = *interm {
+                    match call_lambda(l, arg_cdr, syms) {
+                        Ok(s) => return Ok(s.clone()),
+                        Err(s) => return Err(format!("err in call to lambda: {}", s)),
+                    }
+                } else {
+                    car = interm;
+                }
+            },
 
             Ctr::Symbol(ref tok) => {
                 let outer_scope_seg_holder: Seg;

src/segment.rs

@@ -244,7 +244,7 @@ impl Clone for Ctr {
             Ctr::Float(s) => Ctr::Float(*s),
             Ctr::Bool(s) => Ctr::Bool(*s),
             Ctr::Seg(s) => Ctr::Seg(s.clone()),
-            Ctr::Lambda(s) => Ctr::Seg(s.clone()),
+            Ctr::Lambda(s) => Ctr::Lambda(s.clone()),
             Ctr::None => Ctr::None,
         }
     }

src/stl.rs

@@ -492,6 +492,17 @@ pub fn static_stdlib(syms: &mut SymTable) -> Result<(), String> {
         },
     );
 
+    syms.insert(
+        "lambda".to_string(),
+        Symbol {
+            name: String::from("lambda"),
+            args: Args::Lazy(2),
+            conditional_branches: true,
+            docs: decl::LAMBDA_DOCSTRING.to_string(),
+            value: ValueType::Internal(Rc::new(decl::lambda_callback)),
+        }
+    );
+
     Ok(())
 }
 

src/stl/boolean.rs

@@ -127,7 +127,6 @@ Integers and Floats will cast to true if they are 0 and false otherwise.";
 pub fn boolcast_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
     match &*ast.car {
         Ctr::Bool(_) => Ok(*ast.car.clone()),
-        Ctr::Symbol(_) => Err("not clear how to cast a symbol to a bool".to_string()),
         Ctr::String(s) => {
             if s == "true" {
                 Ok(Ctr::Bool(true))
@@ -139,7 +138,7 @@ pub fn boolcast_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String>
         },
         Ctr::Integer(i) => Ok(Ctr::Bool(*i == 0)),
         Ctr::Float(f) => Ok(Ctr::Bool(*f == 0.0)),
-        Ctr::Seg(_) => Err("cannot convert list to a boolean".to_string()),
+        _ => Err(format!("cannot convert a {} to a boolean",
-        Ctr::None => Err("Impossible task: cannot convert none to bool".to_string()),
+                         ast.car.to_type())),
     }
 }

src/stl/control.rs

@@ -17,7 +17,7 @@
 
 use crate::eval::eval;
 use crate::segment::{Ctr, Seg};
-use crate::sym::{Args, SymTable, Symbol, ValueType};
+use crate::sym::{SymTable, Symbol};
 
 pub const IF_DOCSTRING: &str =
     "accepts three bodies, a condition, an unevaluated consequence, and an alternative consequence.
@@ -151,15 +151,15 @@ pub fn let_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
 
                     localsyms.insert(
                         name.clone(),
-                        Symbol {
+                        Symbol::from_ast(
-                            name: name.clone(),
+                            name, &"variable used in let form".to_string(),
-                            args: Args::None,
+                            &Seg::from_mono(Box::new(*var_val_res.unwrap().clone())),
-                            conditional_branches: false,
+                            None),
-                            docs: "variable used in let form".to_string(),
-                            value: ValueType::VarForm(Box::new(*var_val_res.unwrap().clone())),
-                        },
                     );
                 }
+            } else if let Ctr::None = *var_form.car {
+                // nothing to declare
+                return true;
             } else {
                 eprintln!("improper declaration of {}: not a list", var_decl);
                 return false;
@@ -176,6 +176,7 @@ pub fn let_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, String> {
     let mut result: Box<Ctr> = Box::new(Ctr::None);
     if !eval_forms.circuit(&mut |eval_form: &Ctr| -> bool {
         let res: Result<Box<Ctr>, String>;
+        println!("let: {}", eval_form);
         if let Ctr::Seg(ref eval_tree) = eval_form {
             res = eval(&eval_tree, &mut localsyms);
         } else {

src/stl/decl.rs

@@ -17,7 +17,7 @@
 
 use crate::eval::eval;
 use crate::segment::{Ctr, Seg};
-use crate::sym::{Args, SymTable, Symbol, UserFn, ValueType};
+use crate::sym::{SymTable, Symbol, UserFn, ValueType};
 use std::env;
 
 pub const QUOTE_DOCSTRING: &str = "takes a single unevaluated tree and returns it as it is: unevaluated.";
@@ -101,6 +101,7 @@ pub const STORE_DOCSTRING: &str = "allows user to define functions and variables
      (def useless-var)";
 
 pub fn store_callback(ast: &Seg, syms: &mut SymTable, env_cfg: bool) -> Result<Ctr, String> {
+    println!("def: {}", ast);
     let is_var = ast.len() == 3;
     if let Ctr::Symbol(ref identifier) = *ast.car {
         match &*ast.cdr {
@@ -109,27 +110,40 @@ pub fn store_callback(ast: &Seg, syms: &mut SymTable, env_cfg: bool) -> Result<C
                 if let Ctr::String(ref doc) = *doc_tree.car {
                     match &*doc_tree.cdr {
                         // define a variable
-                        Ctr::Seg(data_tree) if is_var => match eval(&Box::new(data_tree), syms) {
+                        Ctr::Seg(data_tree) if is_var => {
-                            Ok(seg) => {
+                            let eval_arg: &Seg;
-                                if let Ctr::Seg(ref val) = *seg {
+                            let outer_maybe_eval_seg: Seg;
+                            let mut expand = false;
+                            if let Ctr::Seg(ref eval_me) = *data_tree.car {
+                                eval_arg = eval_me;
+                            } else {
+                                outer_maybe_eval_seg = Seg::from_mono(data_tree.car.clone());
+                                eval_arg = &outer_maybe_eval_seg;
+                                expand = true;
+                            }
+                            match eval(eval_arg, syms) {
+                                Ok(ctr) => {
+                                    let mut body = ctr;
+                                    if expand {
+                                        if let Ctr::Seg(ref s) = *body {
+                                            body = s.car.clone();
+                                        } else {
+                                            return Err("impossible expansion".to_string())
+                                        }
+                                    }
                                     syms.insert(
                                         identifier.clone(),
-                                        Symbol {
+                                        Symbol::from_ast(
-                                            value: ValueType::VarForm(val.car.clone()),
+                                            identifier, doc,
-                                            name: identifier.clone(),
+                                            &Seg::from_mono(body.clone()), None
-                                            args: Args::None,
+                                        ),
-                                            docs: doc.to_owned(),
-                                            conditional_branches: false,
-                                        },
                                     );
                                     if env_cfg {
-                                        env::set_var(identifier.clone(), val.car.to_string());
+                                        env::set_var(identifier.clone(), body.to_string());
-                                    }
-                                } else {
-                                    return Err("impossible args to export".to_string());
                                     }
                                 }
                                 Err(e) => return Err(format!("couldnt eval symbol: {}", e)),
+                            }
                         },
 
                         // define a function
@@ -157,16 +171,10 @@ pub fn store_callback(ast: &Seg, syms: &mut SymTable, env_cfg: bool) -> Result<C
                                 if let Ctr::Seg(ref bodies) = *data_tree.cdr {
                                     syms.insert(
                                         identifier.clone(),
-                                        Symbol {
+                                        Symbol::from_ast(
-                                            value: ValueType::FuncForm(UserFn {
+                                            identifier, doc, bodies,
-                                                ast: Box::new(bodies.clone()),
+                                            Some(arg_list),
-                                                arg_syms: arg_list.clone(),
+                                        ),
-                                            }),
-                                            name: identifier.clone(),
-                                            args: Args::Lazy(arg_list.len() as u128),
-                                            docs: doc.to_owned(),
-                                            conditional_branches: false,
-                                        },
                                     );
                                 } else {
                                     return Err(
@@ -266,6 +274,9 @@ pub fn lambda_callback(
             if let Ctr::Symbol(ref s) = *arg {
                 args.push(s.clone());
                 true
+            } else if let Ctr::None = *arg {
+                // no args case
+                true
             } else {
                 false
             }
@@ -273,10 +284,14 @@ pub fn lambda_callback(
             Err("all elements of first argumnets must be symbols".to_string())
         } else {
             if let Ctr::Seg(ref eval_head) = *ast.cdr {
+                if let Ctr::Seg(_) = *eval_head.car {
                     Ok(Ctr::Lambda(UserFn{
                         ast: Box::new(eval_head.clone()),
                         arg_syms: args,
                     }))
+                } else {
+                    Err("function body must be in list form".to_string())
+                }
             } else {
                 Err("not enough args".to_string())
             }

src/stl/strings.rs

@@ -46,6 +46,7 @@ pub fn concat_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
             Ctr::Float(f) => string.push_str(&f.to_string()),
             Ctr::Bool(b) => string.push_str(&b.to_string()),
             Ctr::Seg(c) => string.push_str(&c.to_string()),
+            Ctr::Lambda(l) => string.push_str(&l.to_string()),
             Ctr::None => (),
         }
         true
@@ -67,6 +68,7 @@ pub fn strlen_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
         Ctr::Float(f) => Ok(Ctr::Integer(f.to_string().len() as i128)),
         Ctr::Bool(b) => Ok(Ctr::Integer(b.to_string().len() as i128)),
         Ctr::Seg(c) => Ok(Ctr::Integer(c.to_string().len() as i128)),
+        Ctr::Lambda(l) => Ok(Ctr::Integer(l.to_string().len() as i128)),
         // highly suspicious case below
         Ctr::None => Ok(Ctr::Integer(0)),
     }
@@ -83,6 +85,7 @@ pub fn strcast_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String>
         Ctr::Float(f) => Ok(Ctr::String(f.to_string())),
         Ctr::Bool(b) => Ok(Ctr::String(b.to_string())),
         Ctr::Seg(c) => Ok(Ctr::String(c.to_string())),
+        Ctr::Lambda(l) => Ok(Ctr::String(l.to_string())),
         // highly suspicious case below
         Ctr::None => Ok(Ctr::String(String::new())),
     }

src/sym.rs

@@ -229,11 +229,15 @@ impl fmt::Display for Args {
 
 impl fmt::Display for UserFn {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "(lambda: (");
+        write!(f, "(lambda (")?;
-        for i in self.arg_syms {
+        let mut arg_iter = (&self.arg_syms).into_iter();
-            write!(f, "{} ", i);
+        if let Some(elem) = arg_iter.next() {
+            write!(f, "{}", elem)?;
+            for i in arg_iter {
+                write!(f, " {}", i)?;
             }
-        write!(f, ") {})", self.ast);
+        }
+        write!(f, ") {})", self.ast.car)?;
 
         Ok(())
     }
@@ -265,12 +269,7 @@ impl Symbol {
         let outer_scope_seg_storage: Seg;
         let outer_scope_eval: Box<Ctr>;
         if !self.conditional_branches {
-            let outer_scope_eval_result = eval(args, syms);
+            outer_scope_eval = eval(args, syms)?;
-            // dont listen to clippy. using ? will move the value.
-            if let Err(s) = outer_scope_eval_result {
-                return Err(s);
-            }
-            outer_scope_eval = outer_scope_eval_result.unwrap();
             match *outer_scope_eval {
                 Ctr::Seg(ref segment) => evaluated_args = segment,
                 _ => {
@@ -282,6 +281,7 @@ impl Symbol {
             evaluated_args = args;
         }
 
+        println!("args: {}", evaluated_args);
         self.args.validate_inputs(evaluated_args)?;
         match &self.value {
             ValueType::VarForm(ref f) => Ok(Box::new(*f.clone())),
@@ -351,4 +351,64 @@ impl Symbol {
             }
         }
     }
+
+    pub fn from_ast(
+        id: &String,
+        doc: &String,
+        ast: &Seg,
+        arg_list: Option<Vec<String>>,
+    ) -> Symbol {
+        let args: Args;
+        let value: ValueType;
+
+        if let Some(ref arg_syms) = arg_list {
+            println!("def a func form");
+            value = ValueType::FuncForm(UserFn{
+                ast: Box::new(ast.clone()),
+                arg_syms: arg_syms.clone(),
+            });
+            args = Args::Lazy(arg_syms.len() as u128);
+        } else if let Ctr::Lambda(ref l) = *ast.car {
+            println!("def a func form (lambda)");
+            args = Args::Lazy(l.arg_syms.len() as u128);
+            value = ValueType::FuncForm(l.clone());
+        } else {
+            println!("def a var form");
+            args = Args::None;
+            value = ValueType::VarForm(ast.car.clone());
+        }
+
+        Symbol {
+            name: id.clone(),
+            docs: doc.clone(),
+            conditional_branches: false,
+            args, value,
+        }
+    }
+}
+
+pub fn call_lambda(
+    lam: &UserFn,
+    args_ctr: &Box<Ctr>,
+    syms: &mut SymTable,
+) -> Result<Box<Ctr>, String> {
+    let temp_sym = Symbol {
+        name: String::from("anonymous"),
+        conditional_branches: false,
+        docs: String::from("user defined lambda"),
+        args: Args::Lazy(lam.arg_syms.len() as u128),
+        value: ValueType::FuncForm(lam.clone()),
+    };
+
+    let args: &Seg;
+    let outer_scope_maybe_args: Seg;
+    if let Ctr::Seg(ref args_head) = **args_ctr {
+        args = args_head;
+    } else {
+        outer_scope_maybe_args = Seg::from_mono(
+            Box::new(*args_ctr.clone()));
+        args = &outer_scope_maybe_args;
+    }
+
+    temp_sym.call(args, syms)
 }

tests/test_lib_decl.rs

@@ -1,4 +1,4 @@
-mod var_lib_tests {
+mod decl_lib_tests {
     use relish::ast::{eval, lex, Ctr, SymTable};
     use relish::stdlib::{dynamic_stdlib, static_stdlib};
 
@@ -297,4 +297,86 @@ mod var_lib_tests {
             result.to_string(),
         );
     }
+
+    #[test]
+    fn test_lambda_str_equivalency_list() {
+        let document = "(lambda (x y) (add x y))";
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+        assert_eq!(
+            *eval(&lex(&document.to_string()).unwrap(), &mut syms)
+                .unwrap()
+                .to_string(),
+            document.to_string(),
+        );
+    }
+
+    #[test]
+    fn test_lambda_str_equivalency_no_args() {
+        let document = "(lambda () (add 1 2))";
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+        assert_eq!(
+            *eval(&lex(&document.to_string()).unwrap(), &mut syms)
+                .unwrap()
+                .to_string(),
+            document.to_string(),
+        );
+    }
+
+    #[test]
+    fn test_lambda_inline_call() {
+        let document = "((lambda (x y) (add x y)) 1 2)";
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+        let it = *eval(
+            &lex(&document.to_string()).unwrap(),
+            &mut syms).unwrap();
+        println!("final return: {}", it);
+        if let Ctr::Integer(i) = it {
+            assert_eq!(i, 3)
+        } else {
+            panic!()
+        }
+    }
+
+    #[test]
+    fn test_lambda_let_call() {
+        let document = "(let ((adder (lambda (x y) (add x y))))
+            (adder 1 2))";
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+                let it = *eval(
+            &lex(&document.to_string()).unwrap(),
+            &mut syms).unwrap();
+        println!("{}", it);
+        if let Ctr::Integer(i) = it {
+            assert_eq!(i, 3)
+        } else {
+            panic!()
+        }
+    }
+
+    #[test]
+    fn test_lambda_var_bound_call() {
+        let document = "(let (())
+            (def adder 'my adder' (lambda (x y) (add x y)))
+            (adder 1 2))";
+        let mut syms = SymTable::new();
+        static_stdlib(&mut syms).unwrap();
+        dynamic_stdlib(&mut syms).unwrap();
+        let it = *eval(
+            &lex(&document.to_string()).unwrap(),
+            &mut syms).unwrap();
+        println!("{}", it);
+        if let Ctr::Integer(i) = it {
+            assert_eq!(i, 3)
+        } else {
+            panic!()
+        }
+    }
 }