schemers/src/primitives.rs

use crate::interpreter::has_tag;
use crate::interpreter::is_true;
use crate::parser::make_symbol;
use crate::parser::Datum;
use crate::parser::Datum::*;
use std::io;
use std::io::prelude::*;
use std::mem;

pub fn add(mut args: Vec<Datum>) -> Datum {
    let mut r = 0;
    for i in 1..args.len() {
        let datum = mem::take(&mut args[i]);
        if let Number(n) = datum {
            r += n;
        } else {
            panic!("ADD -- not-all-args-are-numbers {:?}", args)
        }
    }
    Number(r)
}

pub fn mul(mut args: Vec<Datum>) -> Datum {
    let mut r = 1;
    for i in 1..args.len() {
        let datum = mem::take(&mut args[i]);
        if let Number(n) = datum {
            r *= n;
        } else {
            panic!("MUL -- not-all-args-are-numbers {:?}", args)
        }
    }
    Number(r)
}

pub fn sub(mut args: Vec<Datum>) -> Datum {
    if args.len() == 2 {
        let datum = mem::take(&mut args[1]);
        if let Number(n) = datum {
            return Number(-n);
        } else {
            panic!("SUB -- not-all-args-are-numbers {:?}", args)
        }
    }

    let mut r;
    let datum = mem::take(&mut args[1]);
    if let Number(n) = datum {
        r = n;
    } else {
        panic!("SUB -- not-all-args-are-numbers {:?}", args)
    }

    for i in 2..args.len() {
        let datum = mem::take(&mut args[i]);
        if let Number(n) = datum {
            r -= n;
        } else {
            panic!("SUB -- not-all-args-are-numbers {:?}", args)
        }
    }
    Number(r)
}

pub fn eq(args: Vec<Datum>) -> Datum {
    if args.len() == 1 {
        Boolean(true)
    } else {
        let first = &args[1];
        for i in 2..args.len() {
            let current = &args[i];
            if first != current {
                return Boolean(false);
            }
        }
        Boolean(true)
    }
}

pub fn lt(args: Vec<Datum>) -> Datum {
    if args.len() == 1 {
        Boolean(true)
    } else {
        for i in 1..(args.len() - 1) {
            if &args[i] >= &args[i + 1] {
                return Boolean(false);
            }
        }
        Boolean(true)
    }
}

pub fn or(args: Vec<Datum>) -> Datum {
    if args.len() == 1 {
        Boolean(false)
    } else {
        for i in 1..args.len() {
            if is_true(&args[i]) {
                return args[i].clone();
            }
        }
        Boolean(false)
    }
}

pub fn and(args: Vec<Datum>) -> Datum {
    if args.len() == 1 {
        Boolean(true)
    } else {
        for i in 1..args.len() {
            if !is_true(&args[i]) {
                return Boolean(false);
            }
        }
        args[args.len() - 1].clone()
    }
}

pub fn not(args: Vec<Datum>) -> Datum {
    if args.len() != 2 {
        panic!("NOT -- takes one argument");
    } else {
        if is_true(&args[1]) {
            Boolean(false)
        } else {
            Boolean(true)
        }
    }
}

pub fn display(args: Vec<Datum>) -> Datum {
    for i in 1..args.len() {
        print!("{}", args[i]);
    }
    io::stdout().flush().ok().expect("Could not flush stdout");
    Unspecified
}

pub fn list(mut args: Vec<Datum>) -> Datum {
    args[0] = make_symbol("list");
    Datum::List(args)
}

pub fn cons(mut args: Vec<Datum>) -> Datum {
    if args.len() != 3 {
        panic!("CONS -- two args expected {:?}", args);
    }
    let a = std::mem::take(&mut args[1]);
    let b = std::mem::take(&mut args[2]);
    match b {
        List(b_vec) if has_tag(&b_vec, "list") => {
            let mut r_vec = vec![make_symbol("list"), a];
            r_vec.append(&mut b_vec[1..].to_vec());
            Datum::List(r_vec)
        }
        _ => Datum::Pair(Box::new((a, b))),
    }
}

pub fn car(mut args: Vec<Datum>) -> Datum {
    if args.len() != 2 {
        panic!("CAR -- expected a single arg {:?}", args);
    }
    let a = std::mem::take(&mut args[1]);
    match a {
        List(mut v) if has_tag(&v, "list") => std::mem::take(&mut v[1]),
        Pair(p) => p.0,
        _ => panic!("CAR -- could not get car {:?}", a),
    }
}

pub fn cdr(mut args: Vec<Datum>) -> Datum {
    if args.len() != 2 {
        panic!("CDR -- expected a single arg {:?}", args);
    }
    let a = std::mem::take(&mut args[1]);
    match a {
        List(v) if has_tag(&v, "list") => {
            let mut v_cdr = v[1..].to_vec();
            v_cdr[0] = make_symbol("list");
            List(v_cdr)
        }
        Pair(p) => p.1,
        _ => panic!("CAR -- could not get car {:?}", a),
    }
}

pub fn pair(args: Vec<Datum>) -> Datum {
    if args.len() != 2 {
        panic!("PAIR? -- expected a single arg {:?}", args);
    }
    match &args[1] {
        List(v) if has_tag(&v, "list") => {
            if v.len() == 1 {
                Boolean(false)
            } else {
                Boolean(true)
            }
        }
        Pair(_) => Boolean(true),
        _ => Boolean(false),
    }
}

pub fn null(args: Vec<Datum>) -> Datum {
    if args.len() != 2 {
        panic!("PAIR? -- expected a single arg {:?}", args);
    }
    match &args[1] {
        List(v) if has_tag(&v, "list") => {
            if v.len() == 1 {
                Boolean(true)
            } else {
                Boolean(false)
            }
        }
        Pair(_) => Boolean(false),
        _ => Boolean(false),
    }
}