Evaluator (`eval.rs`)

The evaluator walks an Expr AST and produces a Value, given a variable environment.

Value type

#![allow(unused)]
fn main() {
// defined in env.rs
pub enum Value {
    Scalar(f64),
    Matrix(ndarray::Array2<f64>),
}

pub type Env = HashMap<String, Value>;
}

Scalar is the common case. Matrix was introduced in Phase 3.

AST types

#![allow(unused)]
fn main() {
pub enum Expr {
    Number(f64),
    Var(String),
    UnaryMinus(Box<Expr>),
    BinOp(Box<Expr>, Op, Box<Expr>),
    Call(String, Vec<Expr>),
    Matrix(Vec<Vec<Expr>>),   // outer = rows, inner = elements per row
}

pub enum Op {
    Add, Sub, Mul, Div, Pow,
}
}

`eval(expr, env)` semantics

Variant	Semantics
`Number(n)`	Returns `Scalar(n)`
`Var(name)`	Clones value from `env`; `Err` if not defined
`UnaryMinus(e)`	Negates scalar or every matrix element
`BinOp(l, Div, r)`	`Err` if scalar divisor is `0.0`
`BinOp(l, Pow, r)`	Uses `f64::powf` for scalars; element-wise for `matrix ^ scalar`
`Call(name, args)`	Dispatches to built-in; currently all built-ins require scalar args
`Matrix(rows)`	Evaluates each element (must be scalar), builds `Array2`

Scalar × Matrix arithmetic

Left	Op	Right	Result
`Scalar`	`+` `-` `*` `/`	`Matrix`	element-wise broadcast
`Matrix`	`+` `-` `*` `/` `^`	`Scalar`	element-wise broadcast
`Matrix`	`+` `-`	`Matrix`	element-wise (shapes must match)
`Matrix`	`*` `/` `^`	`Matrix`	error — matrix multiplication is Phase 4

Number display

Three formatters serve different purposes:

`format_value(v, precision, base)` — compact single-line

For scalars: respects the active display base (decimal, hex, bin, oct). For matrices: returns [N×M double].

Used in REPL prompts, who output, and assignment echo for scalars.

`format_scalar(n, precision, base)` — scalar-only

Same as format_value for Scalar values. Used where a scalar is guaranteed (prompt display, base conversion output).

`format_value_full(v, precision)` — full multi-line

Returns None for scalars. For matrices returns a right-aligned column string:

   1   2   3
   4   5   6

Used by the REPL and pipe runner when printing matrix results.

`format_number(n)` — internal / re-parsing

Always decimal, always round-trips through the parser. Used by repl.rs when displaying partial-expression context (e.g. expanding variable names).

`Base` enum

#![allow(unused)]
fn main() {
#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub enum Base { Dec, Hex, Bin, Oct }
}

Carried in repl.rs as the active display mode, passed to format_scalar at output time, switched by hex, dec, bin, oct commands.

Keyboard shortcuts

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