1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146

use crate::grammar::*;
use crate::math::*;
use crate::utils::*;

macro_rules! get_binary_args {
    ($expr:expr, $op:pat) => {
        match $expr.as_ref() {
            Expr::BinaryExpr(BinaryExpr { op: $op, lhs, rhs }) => {
                match (lhs.as_ref(), rhs.as_ref()) {
                    (Expr::Const(l), Expr::Const(r)) => Some((l, r)),
                    _ => None,
                }
            }
            _ => None,
        }
    };
}

macro_rules! get_flattened_binary_args {
    ($expr:expr, $op:expr) => {
        match $expr.as_ref() {
            Expr::BinaryExpr(child) if child.op == $op => {
                Some(get_flattened_binary_args($expr, $op))
            }
            _ => None,
        }
    };
}

macro_rules! get_unary_arg {
    ($expr:expr, $op:pat) => {
        match $expr.as_ref() {
            Expr::UnaryExpr(UnaryExpr { op: $op, rhs }) => Some(rhs.clone()),
            _ => None,
        }
    };
}

pub(super) fn add(expr: RcExpr) -> Option<RcExpr> {
    let span = expr.span;
    let mut args = get_flattened_binary_args!(expr, BinaryOperator::Plus)?;
    let mut konst = 0.;
    let mut i = 0;
    for _ in 0..args.len() {
        match args[i].as_ref() {
            Expr::Const(f) => {
                konst += f;
                args.swap_remove(i);
            }
            _ => i += 1,
        }
    }
    args.push(rc_expr!(konst.into(), span));

    Some(unflatten_binary_expr(
        &args,
        BinaryOperator::Plus,
        UnflattenStrategy::Left,
    ))
}

pub(super) fn subtract(expr: RcExpr) -> Option<RcExpr> {
    let (l, r) = get_binary_args!(expr, BinaryOperator::Minus)?;
    Some(rc_expr!(Expr::Const(l - r), expr.span))
}

pub(super) fn multiply(expr: RcExpr) -> Option<RcExpr> {
    let span = expr.span;
    let mut args = get_flattened_binary_args!(expr, BinaryOperator::Mult)?;
    let mut konst = 1.;
    let mut i = 0;
    for _ in 0..args.len() {
        match args[i].as_ref() {
            Expr::Const(f) => {
                konst *= f;
                args.swap_remove(i);
            }
            _ => i += 1,
        }
    }
    args.push(rc_expr!(konst.into(), span));

    Some(unflatten_binary_expr(
        &args,
        BinaryOperator::Mult,
        UnflattenStrategy::Left,
    ))
}

pub(super) fn divide(expr: RcExpr) -> Option<RcExpr> {
    let og_span = expr.span;
    match expr.as_ref() {
        Expr::BinaryExpr(BinaryExpr {
            op: BinaryOperator::Div,
            lhs,
            rhs,
        }) => match (lhs.as_ref(), rhs.as_ref()) {
            (Expr::Const(l), Expr::Const(r)) => Some(rc_expr!(Expr::Const(l / r), og_span)),
            _ => {
                // Now we try to convert the numerator/denominator into polynomials and cancel them.
                let (numerator, relative_to) = Poly::from_expr(lhs.clone(), None).ok()?;
                let relative_to = match relative_to {
                    Some(e) => e,
                    // Cancelling should only work with term'd polynomials. If the expression has
                    // no terms for whatever reason, let another rule take care of it.
                    None => return None,
                };
                let (denominator, _) =
                    Poly::from_expr(rhs.clone(), Some(relative_to.clone())).ok()?;
                let (_, numerator, denominator) = gcd_poly_zz_heu(numerator, denominator).ok()?;

                // Woo! The polynomials have a gcd we can cancel them with.
                let numer_expr = numerator.to_expr(relative_to.clone(), lhs.span);
                if denominator.is_one() {
                    Some(numer_expr)
                } else {
                    let denom_expr = denominator.to_expr(relative_to, rhs.span);
                    let division = BinaryExpr::div(numer_expr, denom_expr);
                    Some(rc_expr!(Expr::BinaryExpr(division), og_span))
                }
            }
        },
        _ => None,
    }
}

pub(super) fn modulo(expr: RcExpr) -> Option<RcExpr> {
    let (l, r) = get_binary_args!(expr, BinaryOperator::Mod)?;
    Some(rc_expr!(Expr::Const(l % r), expr.span))
}

pub(super) fn exponentiate(expr: RcExpr) -> Option<RcExpr> {
    let (l, r) = get_binary_args!(expr, BinaryOperator::Exp)?;
    Some(rc_expr!(Expr::Const(l.powf(*r)), expr.span))
}

pub(super) fn posate(expr: RcExpr) -> Option<RcExpr> {
    get_unary_arg!(expr, UnaryOperator::SignPositive)
}

pub(super) fn negate(expr: RcExpr) -> Option<RcExpr> {
    match get_unary_arg!(expr, UnaryOperator::SignNegative)?.as_ref() {
        Expr::Const(n) => Some(rc_expr!(Expr::Const(-n), expr.span)),
        _ => None,
    }
}