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use crate::{
app::AppState,
lisp::{
error::{EvalError, LispError},
expr::{Arity, Ident, LispExpr, LispFunction},
number::LispNumber,
Environment,
},
};
use std::convert::TryInto;
use log::{error, info};
pub fn eval(expr: &LispExpr, app: &mut AppState) -> Result<LispExpr, LispError> {
match expr {
LispExpr::Unit => Ok(expr.clone()),
LispExpr::StringLit(_) => Ok(expr.clone()),
LispExpr::Char(_) => Ok(expr.clone()),
LispExpr::Number(_) => Ok(expr.clone()),
LispExpr::BoolLit(_) => Ok(expr.clone()),
LispExpr::Ident(ref id) => lookup_extended(&app.lisp_env, id),
LispExpr::Quote(_, _) => Ok(expr.clone()),
LispExpr::List(li) => {
let func_expr = &li[0];
match func_expr {
LispExpr::Ident(s) => match s.as_ref() {
"define" => define_var(&li[1..], app),
"set!" => set_var(&li[1..], app),
"lambda" => create_lambda(&li[1..]),
"if" => eval_if(&li[1..], app),
_ => {
let func_expr = eval(&func_expr, app)?;
match func_expr {
LispExpr::PrimitiveFunc(f) => {
let mut args = Vec::new();
for item in li[1..].iter() {
args.push(eval(item, app)?);
}
f.call(&args, app)
}
LispExpr::Function(f) => {
let mut args = Vec::new();
for item in li[1..].iter() {
let i = eval(item, app)?;
args.push(i);
}
if f.params.len() != args.len() {
info!("too many or too little number of args");
Err(EvalError::ArgumentCount(Arity::Exact(f.params.len()))
.into())
} else {
let nested_env: Environment =
f.params.into_iter().zip(args).collect();
app.lisp_env.push(nested_env);
let result = if f.body.is_empty() {
Ok(LispExpr::Unit)
} else {
eval(&LispExpr::List(f.body), app)
};
app.lisp_env.pop();
return result;
}
}
_ => Err(EvalError::BadForm.into()),
}
}
},
_ => Err(EvalError::BadForm.into()),
}
}
_ => Err(EvalError::BadForm.into()),
}
}
pub fn define_var(args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, LispError> {
let arity = Arity::Exact(2);
if !arity.is_valid(args) {
return Err(arity.to_error());
}
match args {
[LispExpr::Ident(id), expr] => {
let value = eval(&expr, app)?;
let local_env = app.lisp_env.last_mut();
if let Some(env) = local_env {
env.insert(id.into(), value);
} else {
error!("Unable to create global definition");
return Err(EvalError::BadForm.into());
}
return Ok(LispExpr::Unit);
}
[LispExpr::List(shorthand), LispExpr::List(body)] => {
// (define (func arg) <body>) shorthand
let id = unwrap_ident(shorthand[0].clone());
let params = if shorthand.len() > 1 {
&shorthand[1..]
} else {
&[]
}
.to_vec()
.into_iter()
.map(|arg| arg.try_into())
.collect::<Result<Vec<Ident>, LispError>>()?;
let value = LispExpr::Function(LispFunction {
params,
body: body.to_vec(),
});
let local_env = app.lisp_env.last_mut();
if let Some(env) = local_env {
info!("creating function {}", id);
env.insert(id.into(), value);
} else {
error!("Unable to create global definition");
return Err(EvalError::BadForm.into());
}
return Ok(LispExpr::Unit);
}
_ => {
error!("Invalid usage of `define`");
Err(EvalError::BadForm.into())
}
}
}
pub fn set_var(args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, LispError> {
let arity = Arity::Exact(2);
if !arity.is_valid(args) {
return Err(arity.to_error());
}
match args {
[LispExpr::Ident(id), expr] => {
let value = eval(&expr, app)?;
let local_env = app.lisp_env.last_mut();
if let Some(env) = local_env {
return env
.insert(id.into(), value)
.ok_or(EvalError::UnboundVariable(id.into()).into());
} else {
error!("Unable to set in global env!");
return Err(EvalError::BadForm.into());
}
}
_ => {
error!("Invalid usage of `set!`");
return Err(EvalError::BadForm.into());
}
}
}
pub fn create_lambda(cdr: &[LispExpr]) -> Result<LispExpr, LispError> {
let arity: Arity = Arity::Exact(2);
if !arity.is_valid(cdr) {
return Err(arity.to_error());
}
info!("creating lambda");
match cdr {
[LispExpr::List(params), LispExpr::List(body)]
if params.iter().all(|p| matches!(p, LispExpr::Ident(_))) =>
{
return Ok(LispExpr::Function(LispFunction {
params: params
.into_iter()
.map(|p| unwrap_ident(p.clone()))
.collect::<Vec<_>>(),
body: body.clone(),
}));
}
_ => {
error!("Invalid usage of `lambda`");
return Err(EvalError::BadForm.into());
}
}
}
pub fn eval_if(args: &[LispExpr], app: &mut AppState) -> Result<LispExpr, LispError> {
let arity = Arity::Exact(3);
if !arity.is_valid(args) {
return Err(arity.to_error());
} else {
match args {
[predicate, then, else_] => {
let predicate = eval(&predicate, app)?;
if matches!(predicate, LispExpr::BoolLit(false)) {
return eval(&else_, app);
} else {
return eval(&then, app);
}
}
_ => {
panic!("panicked at `if` expression")
}
}
}
}
pub fn lookup_extended(env_list: &[Environment], key: &str) -> Result<LispExpr, LispError> {
if env_list.is_empty() {
return Err(EvalError::UnboundVariable(key.into()).into());
} else {
let local_env = env_list.last().unwrap();
if let Some(val) = local_env.get(key) {
return Ok(val.clone());
} else {
return lookup_extended(&env_list[..env_list.len() - 1], key);
}
}
}
pub fn unwrap_number(n: &LispExpr) -> &LispNumber {
match n {
LispExpr::Number(i) => i,
_ => panic!("unwrap_number expected number"),
}
}
pub fn unwrap_ident(i: LispExpr) -> String {
match i {
LispExpr::Ident(i) => i,
_ => panic!("unwrap_ident expected string"),
}
}
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