location

Render source-line context with carets under a span.

The same renderer is used for parse errors (single position widened into a one-character span) and runtime errors (whole-expression spans). The interpreter does not depend on this module — the CLI calls it after composing the interpreter’s description and hint.

Types

Span

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A byte-offset range, inclusive of start and exclusive of end. #(0, 0) is treated as “no location” by callers.

pub type Span =
  #(Int, Int)

Values

is_empty

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pub fn is_empty(span: #(Int, Int)) -> Bool

Returns true when a span carries no location information.

source_context

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pub fn source_context(
  source: String,
  span: #(Int, Int),
) -> List(String)

Render the source line(s) containing span with carets underneath.

A zero-width span (#(p, p)) renders a single ^ at column p.
A single-line span renders ^ characters spanning the range.
A multi-line span underlines from the start column to the end of the first line, then renders subsequent lines (up to and including the line containing span.1) with a row of ^s underneath each.