small but full lisp
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50329f1d9f
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0
assets/start.lisp
Normal file
0
assets/start.lisp
Normal file
106
src/environ.rs
106
src/environ.rs
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@ -1,38 +1,78 @@
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use crate::Expr;
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use crate::RispError;
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use crate::HashMap;
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use crate::parse_list_of_floats;
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use crate::Expr;
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use crate::HashMap;
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use crate::RispError;
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pub
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struct Environ {
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pub data: HashMap<String, Expr>,
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macro_rules! ensure_tonicity {
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($check_fn:expr) => {{
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|args: &[Expr]| -> Result<Expr, RispError> {
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let floats = parse_list_of_floats(args)?;
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let first = floats.first().ok_or(RispError::Reason(
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"expected at least one number".to_string(),
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))?;
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let rest = &floats[1..];
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fn f(prev: &f64, xs: &[f64]) -> bool {
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match xs.first() {
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Some(x) => $check_fn(prev, x) && f(x, &xs[1..]),
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None => true,
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}
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};
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Ok(Expr::Bool(f(first, rest)))
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}
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}};
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}
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pub fn env_get(k: &str, env: &Environ) -> Option<Expr> {
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match env.data.get(k) {
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Some(exp) => Some(exp.clone()),
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None => match &env.outer {
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Some(outer_env) => env_get(k, &outer_env),
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None => None,
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},
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}
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}
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pub fn default_env() -> Environ {
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let mut data: HashMap<String, Expr> = HashMap::new();
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data.insert(
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"+".to_string(),
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Expr::Func(
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|args: &[Expr]| -> Result<Expr, RispError> {
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let sum = parse_list_of_floats(args)?.iter().fold(0.0, |sum, a| sum + a);
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Ok(Expr::Number(sum))
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}
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)
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);
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data.insert(
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"-".to_string(),
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Expr::Func(
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|args: &[Expr]| -> Result<Expr, RispError> {
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let floats = parse_list_of_floats(args)?;
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let first = *floats.first().ok_or(RispError::Reason("expected at least one number".to_string()))?;
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let sum_of_rest = floats[1..].iter().fold(0.0, |sum, a| sum + a);
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Ok(Expr::Number(first - sum_of_rest))
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}
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)
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);
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Environ {data}
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#[derive(Clone)]
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pub struct Environ<'a> {
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pub data: HashMap<String, Expr>,
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pub outer: Option<&'a Environ<'a>>,
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}
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pub fn default_env<'a>() -> Environ<'a> {
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let mut data: HashMap<String, Expr> = HashMap::new();
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data.insert(
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"+".to_string(),
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Expr::Func(|args: &[Expr]| -> Result<Expr, RispError> {
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let sum = parse_list_of_floats(args)?
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.iter()
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.fold(0.0, |sum, a| sum + a);
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Ok(Expr::Number(sum))
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}),
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);
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data.insert(
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"-".to_string(),
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Expr::Func(|args: &[Expr]| -> Result<Expr, RispError> {
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let floats = parse_list_of_floats(args)?;
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let first = *floats.first().ok_or(RispError::Reason(
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"expected at least one number".to_string(),
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))?;
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let sum_of_rest = floats[1..].iter().fold(0.0, |sum, a| sum + a);
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Ok(Expr::Number(first - sum_of_rest))
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}),
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);
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data.insert("=".to_string(), Expr::Func(ensure_tonicity!(|a, b| a == b)));
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data.insert(">".to_string(), Expr::Func(ensure_tonicity!(|a, b| a > b)));
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data.insert(
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">=".to_string(),
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Expr::Func(ensure_tonicity!(|a, b| a >= b)),
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);
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data.insert("<".to_string(), Expr::Func(ensure_tonicity!(|a, b| a < b)));
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data.insert(
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"<=".to_string(),
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Expr::Func(ensure_tonicity!(|a, b| a <= b)),
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);
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Environ { data, outer: None }
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}
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169
src/evaluate.rs
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169
src/evaluate.rs
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@ -0,0 +1,169 @@
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use crate::environ::env_get;
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use crate::Environ;
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use crate::Expr;
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use crate::HashMap;
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use crate::RLambda;
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use crate::Rc;
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use crate::RispError;
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pub fn eval(exp: &Expr, env: &mut Environ) -> Result<Expr, RispError> {
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match exp {
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Expr::Symbol(k) => {
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env_get(k, env).ok_or(RispError::Reason(format!("unexpected symbol k='{}'", k)))
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}
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Expr::Bool(_a) => Ok(exp.clone()),
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Expr::Number(_a) => Ok(exp.clone()),
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Expr::List(list) => {
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let first_form = list
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.first()
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.ok_or(RispError::Reason("expected a non-empty list".to_string()))?;
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let arg_forms = &list[1..];
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match eval_built_in_form(first_form, arg_forms, env) {
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Some(res) => res,
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None => {
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let first_eval = eval(first_form, env)?;
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match first_eval {
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Expr::Func(f) => f(&eval_forms(arg_forms, env)?),
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Expr::Lambda(lambda) => {
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let new_env = &mut env_for_lambda(lambda.params_exp, arg_forms, env)?;
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eval(&lambda.body_exp, new_env)
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}
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_ => Err(RispError::Reason(
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"first form must be a function".to_string(),
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)),
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}
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}
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}
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}
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Expr::Func(_) => Err(RispError::Reason("unexpected form".to_string())),
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Expr::Lambda(_) => Err(RispError::Reason("unexpected form".to_string())),
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}
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}
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fn eval_forms(arg_forms: &[Expr], env: &mut Environ) -> Result<Vec<Expr>, RispError> {
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arg_forms.iter().map(|x| eval(x, env)).collect()
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}
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fn env_for_lambda<'a>(
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params: Rc<Expr>,
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arg_forms: &[Expr],
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outer_env: &'a mut Environ,
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) -> Result<Environ<'a>, RispError> {
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let ks = parse_list_of_symbol_strings(params)?;
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if ks.len() != arg_forms.len() {
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return Err(RispError::Reason(format!(
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"expected {} arguments, got {}",
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ks.len(),
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arg_forms.len()
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)));
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}
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let vs = eval_forms(arg_forms, outer_env)?;
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let mut data: HashMap<String, Expr> = HashMap::new();
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for (k, v) in ks.iter().zip(vs.iter()) {
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data.insert(k.clone(), v.clone());
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}
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Ok(Environ {
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data,
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outer: Some(outer_env),
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})
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}
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fn parse_list_of_symbol_strings(form: Rc<Expr>) -> Result<Vec<String>, RispError> {
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let list = match form.as_ref() {
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Expr::List(s) => Ok(s.clone()),
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_ => Err(RispError::Reason(
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"expected args form to be a list".to_string(),
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)),
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}?;
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list.iter()
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.map(|x| match x {
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Expr::Symbol(s) => Ok(s.clone()),
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_ => Err(RispError::Reason(
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"expected symbols in the argument list".to_string(),
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)),
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})
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.collect()
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}
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fn eval_built_in_form(
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exp: &Expr,
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arg_forms: &[Expr],
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env: &mut Environ,
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) -> Option<Result<Expr, RispError>> {
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match exp {
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Expr::Symbol(s) => match s.as_ref() {
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"if" => Some(eval_if_args(arg_forms, env)),
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"def" => Some(eval_def_args(arg_forms, env)),
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"fn" => Some(eval_lambda_args(arg_forms)),
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_ => None,
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},
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_ => None,
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}
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}
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fn eval_lambda_args(arg_forms: &[Expr]) -> Result<Expr, RispError> {
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let params_exp = arg_forms
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.first()
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.ok_or(RispError::Reason("expected args form".to_string()))?;
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let body_exp = arg_forms
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.get(1)
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.ok_or(RispError::Reason("expected second form".to_string()))?;
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if arg_forms.len() > 2 {
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return Err(RispError::Reason(
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"fn definition can only have two forms ".to_string(),
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));
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}
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Ok(Expr::Lambda(RLambda {
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body_exp: Rc::new(body_exp.clone()),
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params_exp: Rc::new(params_exp.clone()),
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}))
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}
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fn eval_if_args(arg_forms: &[Expr], env: &mut Environ) -> Result<Expr, RispError> {
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let test_form = arg_forms
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.first()
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.ok_or(RispError::Reason("expected test form".to_string()))?;
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let test_eval = eval(test_form, env)?;
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match test_eval {
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Expr::Bool(b) => {
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let form_idx = if b { 1 } else { 2 };
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let res_form = arg_forms
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.get(form_idx)
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.ok_or(RispError::Reason(format!("expected form idx={}", form_idx)))?;
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let res_eval = eval(res_form, env);
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res_eval
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}
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_ => Err(RispError::Reason(format!(
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"unexpected test form='{}'",
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test_form.to_string()
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))),
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}
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}
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fn eval_def_args(arg_forms: &[Expr], env: &mut Environ) -> Result<Expr, RispError> {
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let first_form = arg_forms
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.first()
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.ok_or(RispError::Reason("expected first form".to_string()))?;
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let first_str = match first_form {
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Expr::Symbol(s) => Ok(s.clone()),
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_ => Err(RispError::Reason(
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"expected first form to be a symbol".to_string(),
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)),
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}?;
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let second_form = arg_forms
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.get(1)
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.ok_or(RispError::Reason("expected second form".to_string()))?;
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if arg_forms.len() > 2 {
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return Err(RispError::Reason(
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"def can only have two forms ".to_string(),
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));
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}
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let second_eval = eval(second_form, env)?;
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env.data.insert(first_str, second_eval);
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Ok(first_form.clone())
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}
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152
src/main.rs
152
src/main.rs
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@ -1,132 +1,98 @@
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use std::io;
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use std::collections::HashMap;
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use std::fmt;
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use std::io;
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use std::io::Write;
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use std::num::ParseFloatError;
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use std::collections::HashMap;use std::io::Write;
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use std::rc::Rc;
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mod environ;
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use environ::Environ;
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use environ::default_env;
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use environ::Environ;
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mod parser;
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use parser::parse;
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use parser::parse_eval;
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use parser::parse_list_of_floats;
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mod evaluate;
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#[derive(Debug)]
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enum RispError{
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enum RispError {
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Reason(String),
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}
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#[derive(Clone)]
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enum Expr {
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Bool(bool),
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Symbol(String),
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Number(f64),
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List(Vec<Expr>),
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Func(fn(&[Expr]) -> Result<Expr, RispError>), // bam
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Func(fn(&[Expr]) -> Result<Expr, RispError>),
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Lambda(RLambda),
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}
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#[derive(Clone)]
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struct RLambda {
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params_exp: Rc<Expr>,
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body_exp: Rc<Expr>,
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}
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impl fmt::Display for Expr {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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let str = match self {
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Expr::Symbol(s) => s.clone(),
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Expr::Number(n) => n.to_string(),
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Expr::List(list) => {
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let xs: Vec<String> = list
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.iter()
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.map(|x| x.to_string())
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.collect();
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format!("({})", xs.join(","))
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},
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Expr::Func(_) => "Function {}".to_string(),
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};
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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use Expr::*;
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let str = match self {
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Bool(a) => a.to_string(),
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Symbol(s) => s.clone(),
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Number(n) => n.to_string(),
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List(list) => {
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let xs: Vec<String> = list.iter().map(|x| x.to_string()).collect();
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format!("({})", xs.join(","))
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}
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Func(_) => "Function {}".to_string(),
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Lambda(_) => "Lambda {}".to_string(),
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};
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write!(f, "{}", str)
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}
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write!(f, "{}", str)
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}
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}
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fn eval(exp: &Expr, env: &mut Environ) -> Result<Expr, RispError> {
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match exp {
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Expr::Symbol(k) =>
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env.data.get(k)
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.ok_or(
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RispError::Reason(
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format!("unexpected symbol k='{}'", k)
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)
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)
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.map(|x| x.clone())
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,
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Expr::Number(_a) => Ok(exp.clone()),
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Expr::List(list) => {
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let first_form = list
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.first()
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.ok_or(RispError::Reason("expected a non-empty list".to_string()))?;
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let arg_forms = &list[1..];
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let first_eval = eval(first_form, env)?;
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match first_eval {
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Expr::Func(f) => {
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let args_eval = arg_forms
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.iter()
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.map(|x| eval(x, env))
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.collect::<Result<Vec<Expr>, RispError>>();
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f(&args_eval?)
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},
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_ => Err(
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RispError::Reason("first form must be a function".to_string())
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),
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}
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},
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Expr::Func(_) => Err(
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RispError::Reason("unexpected form".to_string())
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),
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}
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}
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fn read_seq<'a>(tokens: &'a [String]) -> Result<(Expr, &'a [String]), RispError> {
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let mut res: Vec<Expr> = vec![];
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let mut xs = tokens;
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loop {
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let (next_token, rest) = xs
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.split_first()
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.ok_or(RispError::Reason("could not find closing `)`".to_string()))
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?;
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if next_token == ")" {
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return Ok((Expr::List(res), rest)) // skip `)`, head to the token after
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let mut res: Vec<Expr> = vec![];
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let mut xs = tokens;
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loop {
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let (next_token, rest) = xs
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.split_first()
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.ok_or(RispError::Reason("could not find closing `)`".to_string()))?;
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if next_token == ")" {
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return Ok((Expr::List(res), rest)); // skip `)`, head to the token after
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}
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let (exp, new_xs) = parse(&xs)?;
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res.push(exp);
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xs = new_xs;
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}
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let (exp, new_xs) = parse(&xs)?;
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res.push(exp);
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xs = new_xs;
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}
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}
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fn slurp_expr() -> String {
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let mut expr = String::new();
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let mut expr = String::new();
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io::stdin().read_line(&mut expr)
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.expect("Failed to read line");
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io::stdin()
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.read_line(&mut expr)
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.expect("Failed to read line");
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expr
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expr
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}
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fn main() {
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let env = &mut default_env();
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loop {
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print!("risp > ");
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let _= std::io::stdout().flush();
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let expr = slurp_expr();
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match parse_eval(expr, env) {
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Ok(res) => println!("-> {}", res),
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Err(e) => match e {
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RispError::Reason(msg) => println!("X> {}", msg),
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},
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let env = &mut default_env();
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loop {
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print!("risp > ");
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let _ = std::io::stdout().flush();
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let expr = slurp_expr();
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match parse_eval(expr, env) {
|
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Ok(res) => println!("-> {}", res),
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Err(e) => match e {
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RispError::Reason(msg) => println!("X> {}", msg),
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},
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}
|
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}
|
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}
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}
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|
|
@ -1,65 +1,57 @@
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use crate::RispError;
|
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use crate::Expr;
|
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use crate::eval;
|
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use crate::Environ;
|
||||
use crate::evaluate::eval;
|
||||
use crate::read_seq;
|
||||
use crate::Environ;
|
||||
use crate::Expr;
|
||||
use crate::ParseFloatError;
|
||||
use crate::RispError;
|
||||
|
||||
pub
|
||||
|
||||
fn tokenize(expr: String) -> Vec<String> {
|
||||
expr
|
||||
.replace("(", " ( ")
|
||||
.replace(")", " ) ")
|
||||
.split_whitespace()
|
||||
.map(|x| x.to_string())
|
||||
.collect()
|
||||
pub fn tokenize(expr: String) -> Vec<String> {
|
||||
expr.replace("(", " ( ")
|
||||
.replace(")", " ) ")
|
||||
.split_whitespace()
|
||||
.map(|x| x.to_string())
|
||||
.collect()
|
||||
}
|
||||
|
||||
pub
|
||||
|
||||
fn parse<'a>(tokens: &'a [String]) -> Result<(Expr, &'a [String]), RispError>{
|
||||
let (token, rest) = tokens.split_first()
|
||||
.ok_or(
|
||||
RispError::Reason("Could not get token".to_string())
|
||||
)?;
|
||||
match &token[..]{
|
||||
"("=>{read_seq(rest)}
|
||||
")"=>Err(RispError::Reason("unexpected `)`".to_string())),
|
||||
_ => Ok((parse_atom(token), rest))
|
||||
pub fn parse<'a>(tokens: &'a [String]) -> Result<(Expr, &'a [String]), RispError> {
|
||||
let (token, rest) = tokens
|
||||
.split_first()
|
||||
.ok_or(RispError::Reason("Could not get token".to_string()))?;
|
||||
match &token[..] {
|
||||
"(" => read_seq(rest),
|
||||
")" => Err(RispError::Reason("unexpected `)`".to_string())),
|
||||
_ => Ok((parse_atom(token), rest)),
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
pub
|
||||
|
||||
fn parse_list_of_floats(args: &[Expr]) -> Result<Vec<f64>, RispError> {
|
||||
args
|
||||
.iter()
|
||||
.map(|x| parse_single_float(x))
|
||||
.collect()
|
||||
pub fn parse_list_of_floats(args: &[Expr]) -> Result<Vec<f64>, RispError> {
|
||||
args.iter().map(|x| parse_single_float(x)).collect()
|
||||
}
|
||||
|
||||
fn parse_single_float(exp: &Expr) -> Result<f64, RispError> {
|
||||
match exp {
|
||||
Expr::Number(num) => Ok(*num),
|
||||
_ => Err(RispError::Reason("expected a number".to_string())),
|
||||
}
|
||||
match exp {
|
||||
Expr::Number(num) => Ok(*num),
|
||||
_ => Err(RispError::Reason("expected a number".to_string())),
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
|
||||
|
||||
fn parse_atom(token: &str) -> Expr {
|
||||
let potential_float: Result<f64, ParseFloatError> = token.parse();
|
||||
match potential_float {
|
||||
Ok(v) => Expr::Number(v),
|
||||
Err(_) => Expr::Symbol(token.to_string().clone())
|
||||
}
|
||||
}pub
|
||||
fn parse_eval(expr: String, env: &mut Environ) -> Result<Expr, RispError> {
|
||||
let (parsed_exp, _) = parse(&tokenize(expr))?;
|
||||
let evaled_exp = eval(&parsed_exp, env)?;
|
||||
|
||||
Ok(evaled_exp)
|
||||
use Expr::*;
|
||||
match token.as_ref() {
|
||||
"true" => Bool(true),
|
||||
"false" => Bool(false),
|
||||
_ => {
|
||||
let potential_float: Result<f64, ParseFloatError> = token.parse();
|
||||
match potential_float {
|
||||
Ok(v) => Number(v),
|
||||
Err(_) => Symbol(token.to_string().clone()),
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
pub fn parse_eval(expr: String, env: &mut Environ) -> Result<Expr, RispError> {
|
||||
let (parsed_exp, _) = parse(&tokenize(expr))?;
|
||||
let evaled_exp = eval(&parsed_exp, env)?;
|
||||
|
||||
Ok(evaled_exp)
|
||||
}
|
||||
Loading…
Reference in a new issue