wolfram_expr/

lib.rs

//! Efficient and ergonomic representation of Wolfram expressions in Rust.

#![allow(clippy::let_and_return)]
#![warn(missing_docs)]

mod array_buf;
mod association;
mod bignum;
mod byte_array;
mod complex;
mod conversion;
mod macros;
mod numeric_array;
mod packed_array;
mod ptr_cmp;
mod wl;
pub mod wxf;
mod wxf_impls;

pub mod symbol;

#[cfg(test)]
mod tests;

mod test_readme {
    //! Ensure that doc tests in the README.md file get run.
    #![doc(hidden)]
    #![doc = include_str!("../README.md")]
}

use std::fmt;
use std::mem;
use std::sync::Arc;

#[doc(inline)]
pub use self::symbol::Symbol;

pub use self::array_buf::{ArrayBuf, ArrayElement, NumericArrayRead};
pub use self::association::{Association, RuleEntry};
pub use self::bignum::{BigInteger, BigReal};
pub use self::byte_array::ByteArray;
pub use self::complex::{Complex32, Complex64};
pub use self::numeric_array::NumericArray;
pub use self::packed_array::PackedArray;
pub use self::wxf::{ExpressionEnum, HeaderEnum, NumericArrayEnum, PackedArrayEnum};

// WXF serialization — the traits, derives, and entry points live in the
// dependency-free `wolfram-serialize` crate; re-exported here for ergonomics.
pub use wolfram_serialize::{
    from_wxf, from_wxf_ref, read_wxf, to_wxf, CompressionLevel, Failure, FromWXF, Reader,
    ToWXF,
};

#[cfg(feature = "unstable_parse")]
pub use self::ptr_cmp::ExprRefCmp;

/// Wolfram Language expression.
///
/// # Example
///
/// Construct the expression `{1, 2, 3}`:
///
/// ```
/// use wolfram_expr::{Expr, Symbol};
///
/// let expr = Expr::normal(Symbol::new("System`List"), vec![
///     Expr::from(1),
///     Expr::from(2),
///     Expr::from(3)
/// ]);
/// ```
///
/// # Reference counting
///
/// Internally, `Expr` is an atomically reference-counted [`ExprKind`]. This makes cloning
/// an expression computationally inexpensive.
#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Expr {
    inner: Arc<ExprKind>,
}

// Assert that Expr has the same size and alignment as a usize / pointer.
const _: () = assert!(mem::size_of::<Expr>() == mem::size_of::<usize>());
const _: () = assert!(mem::size_of::<Expr>() == mem::size_of::<*const ()>());
const _: () = assert!(mem::align_of::<Expr>() == mem::align_of::<usize>());
const _: () = assert!(mem::align_of::<Expr>() == mem::align_of::<*const ()>());

impl Expr {
    /// Construct a new expression from an [`ExprKind`].
    pub fn new(kind: ExprKind) -> Expr {
        Expr {
            inner: Arc::new(kind),
        }
    }

    /// Consume `self` and return an owned [`ExprKind`].
    ///
    /// If the reference count of `self` is equal to 1 this function will *not* perform
    /// a clone of the stored `ExprKind`, making this operation very cheap in that case.
    // Silence the clippy warning about this method. While this method technically doesn't
    // follow the Rust style convention of using `into` to prefix methods which take
    // `self` by move, I think using `to` is more appropriate given the expected
    // performance characteristics of this method. `into` implies that the method is
    // always returning data already owned by this type, and as such should be a very
    // cheap operation. This method can make no such guarantee; if the reference count is
    // 1, then performance is very good, but if the reference count is >1, a deeper clone
    // must be done.
    #[allow(clippy::wrong_self_convention)]
    pub fn to_kind(self) -> ExprKind {
        match Arc::try_unwrap(self.inner) {
            Ok(kind) => kind,
            Err(self_) => (*self_).clone(),
        }
    }

    /// Get the [`ExprKind`] representing this expression.
    pub fn kind(&self) -> &ExprKind {
        &self.inner
    }

    /// Get mutable access to the [`ExprKind`] that represents this expression.
    ///
    /// If the reference count of the underlying shared pointer is not equal to 1, this
    /// will clone the [`ExprKind`] to make it unique.
    pub fn kind_mut(&mut self) -> &mut ExprKind {
        Arc::make_mut(&mut self.inner)
    }

    /// Retrieve the reference count of this expression.
    pub fn ref_count(&self) -> usize {
        Arc::strong_count(&self.inner)
    }

    /// Construct a new normal expression from the head and elements.
    pub fn normal<H: Into<Expr>>(head: H, contents: Vec<Expr>) -> Expr {
        let head = head.into();
        // let contents = contents.into();
        Expr {
            inner: Arc::new(ExprKind::Normal(Normal { head, contents })),
        }
    }

    // TODO: Should Expr's be cached? Especially Symbol exprs? Would certainly save
    //       a lot of allocations.
    /// Construct a new expression from a [`Symbol`].
    pub fn symbol<S: Into<Symbol>>(s: S) -> Expr {
        let s = s.into();
        Expr {
            inner: Arc::new(ExprKind::Symbol(s)),
        }
    }

    /// Construct a new expression from a [`Number`].
    pub fn number(num: Number) -> Expr {
        Expr {
            inner: Arc::new(ExprKind::from(num)),
        }
    }

    /// Construct a new expression from a [`String`].
    pub fn string<S: Into<String>>(s: S) -> Expr {
        Expr {
            inner: Arc::new(ExprKind::String(s.into())),
        }
    }

    /// Construct an expression from a floating-point number.
    ///
    /// ```
    /// # use wolfram_expr::Expr;
    /// let expr = Expr::real(3.14159);
    /// ```
    ///
    /// # Panics
    ///
    /// This function will panic if `real` is NaN.
    pub fn real(real: f64) -> Expr {
        Expr::number(Number::real(real))
    }

    /// Returns the outer-most symbol "tag" used in this expression.
    ///
    /// To illustrate:
    ///
    /// Expression   | Tag
    /// -------------|----
    /// `5`          | `None`
    /// `"hello"`    | `None`
    /// `foo`        | `foo`
    /// `f[1, 2, 3]` | `f`
    /// `g[x][y]`    | `g`
    //
    // TODO: _[x] probably should return None, even though technically
    //       Blank[][x] has the tag Blank.
    // TODO: The above TODO is probably wrong -- tag() shouldn't have any language
    //       semantics built in to it.
    pub fn tag(&self) -> Option<Symbol> {
        match *self.inner {
            ExprKind::Normal(ref normal) => normal.head.tag(),
            ExprKind::Symbol(ref sym) => Some(sym.clone()),
            // Atomic variants (no symbolic head): Integer, Real, String, ByteArray,
            // Association, NumericArray, PackedArray, BigInteger, BigReal.
            _ => None,
        }
    }

    /// If this represents a [`Normal`] expression, return its head. Otherwise, return
    /// `None`.
    pub fn normal_head(&self) -> Option<Expr> {
        match *self.inner {
            ExprKind::Normal(ref normal) => Some(normal.head.clone()),
            _ => None,
        }
    }

    /// Attempt to get the element at `index` of a `Normal` expression.
    ///
    /// Return `None` if this is not a `Normal` expression, or the given index is out of
    /// bounds.
    ///
    /// `index` is 0-based. The 0th index is the first element, not the head.
    ///
    /// This function does not panic.
    pub fn normal_part(&self, index_0: usize) -> Option<&Expr> {
        match self.kind() {
            ExprKind::Normal(ref normal) => normal.contents.get(index_0),
            _ => None,
        }
    }

    /// Returns `true` if `self` is a `Normal` expr with the head `sym`.
    pub fn has_normal_head(&self, sym: &Symbol) -> bool {
        match *self.kind() {
            ExprKind::Normal(ref normal) => normal.has_head(sym),
            _ => false,
        }
    }

    //==================================
    // Common values
    //==================================

    /// [`Null`](https://reference.wolfram.com/language/ref/Null.html) <sub>WL</sub>.
    pub fn null() -> Expr {
        crate::expr!(System::Null)
    }

    //==================================
    // Convenience creation functions
    //==================================

    /// Construct a new `Rule[_, _]` expression from the left-hand side and right-hand
    /// side.
    ///
    /// # Example
    ///
    /// Construct the expression `FontSize -> 16`:
    ///
    /// ```
    /// use wolfram_expr::{Expr, Symbol};
    ///
    /// let option = Expr::rule(Symbol::new("System`FontSize"), Expr::from(16));
    /// ```
    pub fn rule<LHS: Into<Expr>>(lhs: LHS, rhs: Expr) -> Expr {
        let lhs = lhs.into();
        crate::expr!(System::Rule[lhs, rhs])
    }
    /// Construct a new `RuleDelayed[_, _]` expression from the left-hand side and right-hand
    /// side.
    ///
    /// # Example
    ///
    /// Construct the expression `x :> RandomReal[]`:
    ///
    /// ```
    /// use wolfram_expr::{Expr, Symbol};
    ///
    /// let delayed = Expr::rule_delayed(
    ///     Symbol::new("Global`x"),
    ///     Expr::normal(Symbol::new("System`RandomReal"), vec![])
    /// );
    /// ```
    pub fn rule_delayed<LHS: Into<Expr>>(lhs: LHS, rhs: Expr) -> Expr {
        let lhs = lhs.into();
        crate::expr!(System::RuleDelayed[lhs, rhs])
    }

    /// Construct a new `List[...]`(`{...}`) expression from it's elements.
    ///
    /// # Example
    ///
    /// Construct the expression `{1, 2, 3}`:
    ///
    /// ```
    /// use wolfram_expr::Expr;
    ///
    /// let list = Expr::list(vec![Expr::from(1), Expr::from(2), Expr::from(3)]);
    /// ```
    pub fn list(elements: Vec<Expr>) -> Expr {
        // `..elements` splices the Vec; the in-place `collect` reuses its
        // allocation (no realloc), so this is as cheap as the direct form.
        crate::expr!(System::List[..elements])
    }
}

/// Wolfram Language expression variants.
///
/// Marked `#[non_exhaustive]` so that future variant additions (for new WXF wire types,
/// etc.) are non-breaking. Downstream `match` expressions over `ExprKind` from outside
/// this crate must include a `_ => …` arm.
#[allow(missing_docs)]
#[non_exhaustive]
#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum ExprKind<E = Expr> {
    Integer(i64),
    Real(F64),
    String(String),
    Symbol(Symbol),
    Normal(Normal<E>),
    // WXF-derived variants:
    ByteArray(ByteArray),
    Association(Association),
    NumericArray(NumericArray),
    PackedArray(PackedArray),
    BigInteger(BigInteger),
    BigReal(BigReal),
}

/// Wolfram Language "normal" expression: `f[...]`.
///
/// A *normal* expression is any expression that consists of a head and zero or
/// more arguments.
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Normal<E = Expr> {
    /// The head of this normal expression.
    head: E,

    /// The elements of this normal expression.
    ///
    /// If `head` conceptually represents a function, these are the arguments that are
    /// being applied to `head`.
    contents: Vec<E>,
}

/// Subset of [`ExprKind`] that covers number-type expression values.
#[allow(missing_docs)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum Number {
    // TODO: Rename this to MachineInteger
    Integer(i64),
    // TODO: Make an explicit MachineReal type which hides the inner f64, so that other
    //       code can make use of WL machine reals with a guaranteed type. In
    //       particular, change wl_compile::mir::Constant to use that type.
    Real(F64),
}

/// 64-bit floating-point real number. Not NaN.
pub type F64 = ordered_float::NotNan<f64>;
/// 32-bit floating-point real number. Not NaN.
pub type F32 = ordered_float::NotNan<f32>;

//=======================================
// Type Impl's
//=======================================

impl Normal {
    /// Construct a new normal expression from the head and elements.
    pub fn new<E: Into<Expr>>(head: E, contents: Vec<Expr>) -> Self {
        Normal {
            head: head.into(),
            contents,
        }
    }

    /// The head of this normal expression.
    pub fn head(&self) -> &Expr {
        &self.head
    }

    /// The elements of this normal expression.
    ///
    /// If `head` conceptually represents a function, these are the arguments that are
    /// being applied to `head`.
    pub fn elements(&self) -> &[Expr] {
        &self.contents
    }

    /// The elements of this normal expression.
    ///
    /// Use [`Normal::elements()`] to get a reference to this value.
    pub fn into_elements(self) -> Vec<Expr> {
        self.contents
    }

    /// Returns `true` if the head of this expression is `sym`.
    pub fn has_head(&self, sym: &Symbol) -> bool {
        self.head == *sym
    }
}

impl Number {
    /// # Panics
    ///
    /// This function will panic if `r` is NaN.
    ///
    /// TODO: Change this function to take `NotNan` instead, so the caller doesn't have to
    ///       worry about panics.
    pub fn real(r: f64) -> Self {
        let r = match ordered_float::NotNan::new(r) {
            Ok(r) => r,
            Err(_) => panic!("Number::real: got NaN"),
        };
        Number::Real(r)
    }
}

//=======================================
// Display & Debug impl/s
//=======================================

impl fmt::Debug for Expr {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let Expr { inner } = self;
        write!(f, "{:?}", inner)
    }
}


//======================================
// Comparision trait impls
//======================================

impl PartialEq<Symbol> for Expr {
    fn eq(&self, other: &Symbol) -> bool {
        match self.kind() {
            ExprKind::Symbol(self_sym) => self_sym == other,
            _ => false,
        }
    }
}