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|
use super::ast;
use super::runtime::{advance_v, Term, Value};
use std::fmt;
use std::rc::Rc;
#[derive(Debug, Clone, PartialEq)]
pub struct Builtin {
pub identifier: &'static str,
pub arguments: Vec<Value>,
pub n_arguments: usize,
}
impl Builtin {
pub fn new(identifier: &'static str, n_arguments: usize) -> Builtin {
Builtin {
identifier: identifier,
arguments: vec![],
n_arguments: n_arguments,
}
}
pub fn bind_arg(&self, arg: &Value) -> Builtin {
let mut new_args = self.arguments.clone();
new_args.push(arg.clone());
Builtin {
identifier: self.identifier,
arguments: new_args,
n_arguments: self.n_arguments - 1,
}
}
}
impl fmt::Display for Builtin {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut arg_str = String::new();
for argument in &self.arguments {
arg_str.push_str(format!(" {}", argument).as_str());
}
write!(f, "Builtin({}){}", self.identifier, arg_str)
}
}
fn argument_type_error(builtin_id: &'static str, arg: &Value) -> Result<(Rc<Term>, usize), String> {
Err(format!(
"[runtime] cannot apply builtin {} to argument {}",
builtin_id, arg
))
}
fn argument_n_error(builtin_id: &'static str, n: usize) -> Result<(Rc<Term>, usize), String> {
Err(format!(
"[runtime] builtin {} can not accept an argument with n {}",
builtin_id, n
))
}
pub const B_INTEGER_EQ: &str = "int.eq?";
pub const B_INTEGER_INCREMENT: &str = "int.increment";
pub const B_INTEGER_ADD: &str = "int.add";
pub fn make_boolean_true_function() -> Term {
let x = advance_v();
let y = advance_v();
Term::Abstraction(x, Rc::new(Term::Abstraction(y, Rc::new(Term::Variable(x)))))
}
pub fn make_boolean_false_function() -> Term {
let x = advance_v();
let y = advance_v();
Term::Abstraction(x, Rc::new(Term::Abstraction(y, Rc::new(Term::Variable(y)))))
}
pub fn make_identity_function() -> Term {
let v = advance_v();
Term::Abstraction(v, Rc::new(Term::Variable(v)))
}
pub fn try_ast_symbol_to_builtin_term(symbol: &ast::Symbol) -> Option<Term> {
let builtin = match symbol.as_str() {
"true" => return Some(make_boolean_true_function()),
"false" => return Some(make_boolean_false_function()),
"id" => return Some(make_identity_function()),
B_INTEGER_EQ => Builtin::new(B_INTEGER_EQ, 2),
B_INTEGER_INCREMENT => Builtin::new(B_INTEGER_INCREMENT, 1),
B_INTEGER_ADD => Builtin::new(B_INTEGER_ADD, 2),
_ => return None,
};
Some(Term::Builtin(builtin))
}
pub fn evaluate_builtin(builtin: &Builtin, rhs: Rc<Term>) -> Result<(Rc<Term>, usize), String> {
let result_term = match builtin.identifier {
B_INTEGER_EQ => match &*rhs {
Term::Primitive(primitive) => match primitive {
Value::Integer(value) => match builtin.n_arguments {
2 => Term::Builtin(builtin.bind_arg(primitive)),
1 => {
let other = &builtin.arguments[0];
match other {
Value::Integer(other_value) => {
if value == other_value {
make_boolean_true_function()
} else {
make_boolean_false_function()
}
}
other => return argument_type_error(builtin.identifier, other),
}
}
_ => return argument_n_error(builtin.identifier, builtin.n_arguments),
},
other => return argument_type_error(builtin.identifier, other),
},
_ => return Ok((Rc::new(Term::Builtin(builtin.clone())), 0)),
},
B_INTEGER_INCREMENT => match &*rhs {
Term::Primitive(primitive) => match primitive {
Value::Integer(value) => Term::Primitive(Value::Integer(value + 1)),
other => return argument_type_error(builtin.identifier, other),
},
_ => return Ok((Rc::new(Term::Builtin(builtin.clone())), 0)),
},
B_INTEGER_ADD => match &*rhs {
Term::Primitive(primitive) => match primitive {
Value::Integer(value) => match builtin.n_arguments {
2 => Term::Builtin(builtin.bind_arg(primitive)),
1 => {
let other = &builtin.arguments[0];
match other {
Value::Integer(other_value) => {
Term::Primitive(Value::Integer(value + other_value))
}
other => return argument_type_error(builtin.identifier, other),
}
}
_ => return argument_n_error(builtin.identifier, builtin.n_arguments),
},
other => return argument_type_error(builtin.identifier, other),
},
_ => return Ok((Rc::new(Term::Builtin(builtin.clone())), 0)),
},
_ => {
return Err(format!(
"[runtime] invalid builtin evaluated: {}",
builtin.identifier
))
}
};
Ok((Rc::new(result_term), 1))
}
|
