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use crate::{
app::AppState,
lisp::{error::LispError, expr::LispExpr, number::LispNumber, Environment},
};
pub fn is_bound<S: AsRef<str>>(env: &mut Environment, name: S) -> bool {
env.get(name.as_ref()).is_some()
}
pub fn new_binding<S: AsRef<str>>(env: &mut Environment, name: S, value: LispExpr) {
let _ = env.insert(name.as_ref().into(), value);
}
pub fn with_prelude() -> Environment {
let mut env = Environment::new();
new_binding(
&mut env,
"+",
LispExpr::PrimitiveFunc(|args, _| {
if args.iter().any(|arg| !matches!(arg, LispExpr::Number(_))) {
Err(LispError::EvalError)
} else {
let result = args
.iter()
.map(|n| unwrap_number(n))
.fold(LispNumber::Integer(0), |acc, x| acc + *x);
Ok(LispExpr::Number(result))
}
}),
);
env
}
pub fn eval(expr: &LispExpr, app: &mut AppState) -> Result<LispExpr, LispError> {
let env = &mut app.lisp_env;
match expr {
LispExpr::Unit => Ok(expr.clone()),
LispExpr::StringLit(_) => Ok(expr.clone()),
LispExpr::Number(_) => Ok(expr.clone()),
LispExpr::BoolLit(_) => Ok(expr.clone()),
LispExpr::Ident(ref id) => env
.get(id)
.ok_or_else(|| LispError::EvalError)
.map(Clone::clone),
LispExpr::List(li) => {
let head = &li[0];
match head {
LispExpr::Ident(func) => {
let func_expr = env
.get(func)
.map(Clone::clone)
.ok_or_else(|| LispError::EvalError)?;
match func_expr {
LispExpr::PrimitiveFunc(f) => {
let mut args = Vec::new();
for item in li[1..].iter() {
args.push(eval(item, app)?);
}
(f)(&args, None)
}
_ => Err(LispError::EvalError),
}
}
LispExpr::List(_) => {
// TODO
todo!();
}
_ => Err(LispError::EvalError),
}
}
_ => Err(LispError::ParseError),
}
}
pub fn unwrap_number(n: &LispExpr) -> &LispNumber {
match n {
LispExpr::Number(i) => i,
_ => panic!("unwrap_number expected number"),
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn eval_primitive_call() {
let mut env = Environment::new();
new_binding(&mut env, "age", LispExpr::Number(LispNumber::Float(1.4)));
new_binding(
&mut env,
"+",
LispExpr::PrimitiveFunc(|args, _| {
if args.iter().any(|arg| !matches!(arg, LispExpr::Number(_))) {
Err(LispError::EvalError)
} else {
let result = args
.iter()
.map(|n| unwrap_number(n))
.fold(LispNumber::Integer(0), |acc, x| acc + *x);
Ok(LispExpr::Number(result))
}
}),
);
let mut numbers = (1..=3)
.map(LispNumber::Integer)
.map(LispExpr::Number)
.collect::<Vec<_>>();
let mut expr = Vec::new();
expr.push(LispExpr::Ident("+".into()));
expr.append(&mut numbers);
// assert!(matches!(
// eval(&LispExpr::List(expr), ).unwrap(),
// LispExpr::Number(LispNumber::Integer(6))
// ));
}
}
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