Specification: overview

This is the language specification for esque. It describes what the language is, independent of any one implementation. Where features are implemented in the reference compiler esquec they are marked (impl); where they are planned they are marked (planned) with a link to the relevant Planned features page.

The spec was rewritten in v0.10 to remove C-style for and while loops, comprehensions in their old form, and the mut family of mutating operators. The replacement primitives — ranges, tabulate, scan, iterate_until, each, and the reduction operator <op>/ — are laid out in Expressions.

What esque is

esque is:

• a statically typed, expression-oriented language;
• with tensors as first-class values, shapes in the type system, and shape generics dispatched by monomorphisation;
• compiled ahead of time to native code (today: x86-64 Linux ELF);
• pure by default, with an @io effect that propagates through call sites (impl as of v0.13).

esque is not, and is not trying to become:

• a numerical Python replacement (see Triton, JAX);
• a CUDA replacement (the GPU backend is a planned, secondary target);
• a general systems language (memory management is intentionally narrow).

Spec sections

• Lexical — source encoding, tokens.
• Types — primitives, tensor types, shape parameters.
• Expressions — value forms, control, loop primitives.
• Functions — declarations, lambdas, generics.
• Tensors — semantics, layouts, ops.
• Modules — file organisation.

Versioning

Spec versions are aligned with major implementation versions. This document tracks the v0.13 language: the core surface laid down in v0.10, plus extended numerics (v0.11–v0.12), string literals (v0.12), and @io effect typing with a flexible each callee (v0.13).

Feature gates and their target versions live in Planned features → roadmap.