Implementing side-stuff

- Added error severity, mainly to distinguish between READ and EVAL
  errors, can be later expanded to allow other distinction
- Improved repl using the above function (EVAL errors interrupts the
  repl right away, without the need to double-return)
- Added an helper function to provide infos about builtin and composed
  functions
- Possibility to pass files as arguments to setup the environment

Signed-off-by: teo3300 <matteo.rogora@live.it>

src/env.rs

@@ -32,7 +32,7 @@ macro_rules! env_init {
     };
 }
 
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct EnvType {
     data: RefCell<MalMap>,
     outer: Option<Env>,
@@ -62,6 +62,8 @@ pub fn env_get(env: &Env, sym: &String) -> MalRet {
     }
 }
 
+use crate::printer::prt;
+
 pub fn env_binds(outer: Env, binds: &MalType, exprs: &[MalType]) -> Result<Env, String> {
     let env = env_new(Some(outer));
     match binds {
@@ -75,7 +77,7 @@ pub fn env_binds(outer: Env, binds: &MalType, exprs: &[MalType]) -> Result<Env,
                     _ => {
                         return Err(format!(
                             "Initializing environment: {:?} is not a symbol",
-                            bind
+                            prt(bind)
                         ))
                     }
                 }
@@ -90,18 +92,23 @@ use crate::types::MalType::{Fun, Str};
 use crate::types::{arithmetic_op, comparison_op};
 use std::process::exit;
 
+fn panic() -> MalRet {
+    panic!("If this messagge occurs, something went terribly wrong")
+}
+
 pub fn env_init() -> Env {
     env_init!(None,
-              "test" => Fun(|_| Ok(Str("This is a test function".to_string()))),
-              "quit" => Fun(|_| {println!("Bye!"); exit(0)}),
-              "+"    => Fun(|a| arithmetic_op(0, |a, b| a + b, a)),
-              "-"    => Fun(|a| arithmetic_op(0, |a, b| a - b, a)),
-              "*"    => Fun(|a| arithmetic_op(1, |a, b| a * b, a)),
-              "/"    => Fun(|a| arithmetic_op(1, |a, b| a / b, a)),
-              "="    => Fun(|a| comparison_op(|a, b| a == b, a)),
-              ">"    => Fun(|a| comparison_op(|a, b| a >  b, a)),
-              "<"    => Fun(|a| comparison_op(|a, b| a >  b, a)),
-              ">="   => Fun(|a| comparison_op(|a, b| a >= b, a)),
-              "<="   => Fun(|a| comparison_op(|a, b| a <= b, a))
+              "test" => Fun(|_| Ok(Str("This is a test function".to_string())), "Just a test function"),
+              "quit" => Fun(|_| {exit(0)}, "Quits the program with success status (0)"),
+              "help" => Fun(|_| {panic()}, "Gets information about the symbols"),
+              "+"    => Fun(|a| arithmetic_op(0, |a, b| a + b, a), "Returns the sum of the arguments"),
+              "-"    => Fun(|a| arithmetic_op(0, |a, b| a - b, a), "Returns the difference of the arguments"),
+              "*"    => Fun(|a| arithmetic_op(1, |a, b| a * b, a), "Returns the product of the arguments"),
+              "/"    => Fun(|a| arithmetic_op(1, |a, b| a / b, a), "Returns the division of the arguments"),
+              "="    => Fun(|a| comparison_op(|a, b| a == b, a), "Returns true if the arguments are equals, 'nil' otherwise"),
+              ">"    => Fun(|a| comparison_op(|a, b| a >  b, a), "Returns true if the arguments are in strictly descending order, 'nil' otherwise"),
+              "<"    => Fun(|a| comparison_op(|a, b| a >  b, a), "Returns true if the arguments are in strictly ascending order, 'nil' otherwise"),
+              ">="   => Fun(|a| comparison_op(|a, b| a >= b, a), "Returns true if the arguments are in descending order, 'nil' otherwise"),
+              "<="   => Fun(|a| comparison_op(|a, b| a <= b, a), "Returns true if the arguments are in ascending order, 'nil' otherwise")
     )
-}
+}

src/eval.rs

@@ -3,10 +3,11 @@ use crate::env::{env_binds, env_get, env_new, env_set};
 use crate::types::car_cdr;
 use crate::types::MalType::*;
 use crate::types::{MalArgs, MalMap, MalRet, MalType};
+use crate::printer::prt;
 
 fn call_func(func: &MalType, args: &[MalType]) -> MalRet {
     match func {
-        Fun(func) => func(args),
+        Fun(func, _) => func(args),
         MalFun {
             eval,
             params,
@@ -21,7 +22,7 @@ fn call_func(func: &MalType, args: &[MalType]) -> MalRet {
                 _ => Err("This should not happen".to_string()),
             }
         }
-        _ => Err(format!("{:?} is not a function", func)),
+        _ => Err(format!("{:?} is not a function", prt(func))),
     }
 }
 
@@ -56,7 +57,7 @@ fn def_bang_form(list: &[MalType], env: &Env) -> MalRet {
             }
             _ => Err(format!(
                 "def! Assigning {:?} to {:?}, which is not a symbol",
-                &list[1], &list[0]
+                prt(&list[1]), prt(&list[0])
             )),
         },
         _ => Err("def! form: needs 2 arguments".to_string()),
@@ -128,6 +129,23 @@ fn fn_star_form(list: &[MalType], env: Env) -> MalRet {
     })
 }
 
+use crate::printer::print_malfun;
+
+pub fn help_form(list: &[MalType], env: Env) -> MalRet {
+    for sym in list {
+        match sym {
+            Sym(sym_str) => match eval(sym, env.clone())? {
+                Fun(_, desc) => println!("{}\t[builtin]: {}", sym_str, desc),
+                MalFun {params, ast, .. }
+                    => print_malfun(sym_str, *params, *ast),
+                _ => println!("{:?} is not defined as a function", sym_str)
+            }
+            _ => println!("{:?} is not a symbol", prt(sym))
+        }
+    }
+    return Ok(Bool(true));
+}
+
 /// Intermediate function to discern special forms from defined symbols
 fn apply(list: &MalArgs, env: Env) -> MalRet {
     let (car, cdr) = car_cdr(list);
@@ -137,6 +155,7 @@ fn apply(list: &MalArgs, env: Env) -> MalRet {
         Sym(sym) if sym == "do" => do_form(cdr, env),
         Sym(sym) if sym == "if" => if_form(cdr, env),
         Sym(sym) if sym == "fn*" => fn_star_form(cdr, env),
+        Sym(sym) if sym == "help" => help_form(cdr, env),
         // Filter out special forms
         _ => eval_func(&eval_ast(&List(list.to_vec()), env)?),
     }

src/main.rs

@@ -1,20 +1,69 @@
 // io lib to read input and print output
 use std::io::{self, Write};
+use std::env::args;
 
 mod env;
 mod eval;
 mod printer;
 mod reader;
 mod types;
-use env::env_init;
+use env::{Env,env_init};
+use std::fs::File;
+use std::io::{BufReader, BufRead};
 
 mod step4_if_fn_do;
 use step4_if_fn_do::rep;
 
+use crate::types::Severity;
+
+fn load_file(filename: &str, env: &Env) -> io::Result<()> {
+
+    let file = File::open(filename)?;
+    let reader = BufReader::new(file);
+    let mut last: Result<(),()> = Ok(());
+
+    let mut input = String::new();
+    for line in reader.lines() {
+        match line {
+            Ok(line) => {
+                // Read line to compose program input
+                input.push_str(&line);
+
+                if input == ""{continue;}
+
+                match rep(&input, env) {
+                    Ok(_) => {
+                        last = Ok(());
+                        input = String::new()},
+                    Err((err, Severity::Unrecoverable)) => {
+                        last = Ok(());
+                        println!("; Error @ {}", err);
+                    },
+                    _ => {last = Err(())}
+                }
+            },
+            Err(err) => eprintln!("Error reading line: {}", err),
+        }
+    }
+    match last {
+        Err(()) => println!("; ERROR parsing: '{}'\n;   the environment is in an unknown state", filename),
+        _ => {}
+    }
+    Ok(())
+}
+
 fn main() {
-    let mut num = 0;
+
     let reply_env = env_init();
 
+    // setup env
+    let args: Vec<String> = args().collect();
+    for filename in &args[1..] {
+        let _ = load_file(filename, &reply_env);
+    }
+
+    let mut num = 0;
+
     loop {
         let mut input = String::new();
         loop {
@@ -32,11 +81,11 @@ fn main() {
                 // Perform rep on whole available input
                 match rep(&input, &reply_env) {
                     Ok(output) => println!("[{}]> {}", num, output),
-                    Err(err) => {
-                        if line != "\n" {
-                            continue;
+                    Err((err, sev)) => {
+                        if sev == Severity::Recoverable && line != "\n" {
+                            continue
                         }
-                        println!("; [{}]> Error {}", num, err);
+                        println!("; [{}]> Error @ {}", num, err);
                     }
                 }
                 num += 1;

src/printer.rs

@@ -38,7 +38,20 @@ pub fn pr_str(ast: &MalType, print_readably: bool) -> String {
                 .collect::<Vec<String>>()
                 .join(" ")
         ),
-        Fun(func) => format!("{:?}", func),
+        Fun(_, desc) => format!("{}", desc),
         MalFun { .. } => "#<function>".to_string(),
     }
 }
+
+pub fn prt(ast: &MalType) -> String {
+    return pr_str(ast, true)
+}
+
+pub fn print_malfun(sym: &String, params: MalType, ast: MalType) {
+    print!("; {} {}:\n", sym, prt(&params));
+    match ast {
+        List(list) => for el in list {
+            println!(";   {}", prt(&el))},
+        _ => panic!("Function body is not a list")
+    }
+}

src/step4_if_fn_do.rs

@@ -13,13 +13,13 @@ use crate::types::{MalRet, MalType};
 #[allow(non_snake_case)]
 /// Read input and generate an ast
 fn READ(input: &str) -> MalRet {
-    read_str(input).map_err(|err| format!("@ READ: {}", err))
+    read_str(input).map_err(|err| format!("READ: {}", err))
 }
 
 #[allow(non_snake_case)]
 /// Evaluate the generated ast
 fn EVAL(ast: MalType, env: Env) -> MalRet {
-    eval(&ast, env).map_err(|err| format!("@ EVAL: {}", err))
+    eval(&ast, env).map_err(|err| format!("EVAL: {}", err))
 }
 
 #[allow(non_snake_case)]
@@ -28,8 +28,12 @@ fn PRINT(output: MalType) -> String {
     pr_str(&output, true)
 }
 
-pub fn rep(input: &str, env: &Env) -> Result<String, String> {
-    let ast = READ(input)?;
-    let out = EVAL(ast, env.clone())?;
+use crate::types::Severity;
+
+pub fn rep(input: &str, env: &Env) -> Result<String, (String, Severity)> {
+    let ast = READ(input)
+        .map_err(|err| (err, Severity::Recoverable))?;
+    let out = EVAL(ast, env.clone())
+        .map_err(|err| (err, Severity::Unrecoverable))?;
     Ok(PRINT(out))
 }

src/types.rs

@@ -2,12 +2,12 @@ use crate::env::Env;
 use std::collections::HashMap;
 
 // All Mal types should inherit from this
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub enum MalType {
     List(MalArgs),
     Vector(MalArgs),
     Map(MalMap),
-    Fun(fn(&[MalType]) -> MalRet), // Used for base functions, implemented using the underlying language (rust)
+    Fun(fn(&[MalType]) -> MalRet, &'static str), // Used for base functions, implemented using the underlying language (rust)
     MalFun {
         eval: fn(ast: &MalType, env: Env) -> MalRet,
         params: Box<MalType>,
@@ -22,22 +22,19 @@ pub enum MalType {
     Nil,
 }
 
-// Stolen, but this way it's easier to handle errors
+#[derive(PartialEq)]
+pub enum Severity {
+    Recoverable,
+    Unrecoverable
+}
 
-/*
-#[derive(Debug)]
-pub enum MalErr {
-    Str(String), // Messages to the user
-                 // Val(MalType),
-                 // Messages to the program
-} TEMP TEMP  */
 pub type MalErr = String;
-
 pub type MalArgs = Vec<MalType>;
 pub type MalMap = HashMap<String, MalType>;
 pub type MalRet = Result<MalType, MalErr>;
 
 use MalType::{Key, Map, Str};
+use crate::printer::prt;
 
 pub fn make_map(list: MalArgs) -> MalRet {
     if list.len() % 2 != 0 {
@@ -52,7 +49,7 @@ pub fn make_map(list: MalArgs) -> MalRet {
                 let v = &list[i + 1];
                 map.insert(k.to_string(), v.clone());
             }
-            _ => return Err(format!("Map key not valid: {:?}", list[i])),
+            _ => return Err(format!("Map key not valid: {}", prt(&list[i]))),
         }
     }
     Ok(Map(map))
@@ -92,7 +89,7 @@ use MalType::Int;
 fn if_number(val: &MalType) -> Result<isize, String> {
     match val {
         Int(val) => Ok(*val),
-        _ => Err(format!("{:?} is not a number", val)),
+        _ => Err(format!("{:?} is not a number", prt(&val))),
     }
 }
 

test.mal

@@ -0,0 +1,9 @@
+(def! func
+    (fn* (a b c)
+
+        (def! d (+ a b))
+        (- c d)))
+
+(test 1 2 14)
+(help test)
+(quit)