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The Oil Language from 10,000 Feet

This document describes the Oil language. It also discusses future work. Related Documents:

• Oil Language Idioms
• Oil Language Design Notes
• Why Use Oil?

Oil Retains These Shell Concepts

• Commands (pipelines, etc.)
  • ls -l
  • ls -l | wc -l
• Words
  • double quoted
  • interpolation
• Variables
  • use different assigment builtins
• Shell builtins
  • different ones
• Shell functions, loops, and conditionals
  • different syntax

Oil retains them all. A big difference is that keywords rather than builtins are used for assignment.

Syntactic Concepts

See Syntactic Concepts in Oil

The Word Language Is Enhanced

See Oil Word Language.

• Inline Function Calls

Deferred: Static Printf, Formatters

echo ${myfloat %.3f}

Formatters (like template languages)

echo ${myfloat|json}

Special Variables

Special Variables

• @ARGV and ARGV

The Command Language

New Keywords: var, const, setvar

var x = 1

auto for autovivification:

auto dict['key'] += 1

maybe const. I want that to be compile-time though.

return has to be a keyword and not a builtin because it can take arbitrary data types, e.g.

return {name: 'bob', age: 15}

See Oil Keywords.

Shell-Like Builtins

See Oil Builtins.

• Assignment builtins local, declare, export
• Builtins Accept Long Options
  • TODO: Link HN thread

Docstrings and Multiline Commands

Note: not implemented.

##

%%%

The Expression Language is Python-Like

The Expression Language Is Mostly Python

See Oil Expressions.

• list, dict literals
• list comprehensions

Builtin Functions

Python and shell both borrow from C. Oil borrows from Python and C.

• len(): str, array, dict
• min, max: int, float
• any, all: truthiness? Are non-empty strings truthy though?
  • that's a constraint of 'tea'
• reversed() --- this can be done with tac and QSN!
• sorted() ? -- Does QSN have a lexicographical mapping for this?
  • or write sort --qsn?
• sum()
  • this can be written with a 'wok' filter that runs in process?
• enumerate, zip: these return tuples. Not sure I want to implement them.

Runtime Semantics

Data Structures

• bash-like data structures at first
• fully recursive

Data Types Are Mostly Python?

• "JSON" types in Python: dict, heterogeneous list
• homogeneous string arrays like shell
• homogeneous bool/int/float arrays like R / NumPy

Process Model

• Process Model

Simple Word Evaluation With shopt -s simple_word_eval

Mentioned in the last post. This is big!

Scope and Namespaces

• Like shell and Python, there is a global scope and function scope..
• shell functions don't live in their own scope? This is like Lisp-1 vs Lisp-2.
• There won't be dynamic scope as in shell.

The use builtin will provide scope.

Deferred Features

• Coprocesses
• Data Frames from R
  • Have to get dict/list/etc. working first
  • date and time types
• Low Level Bindings for POSIX, Linux, Containers
• Find Dialect
  • replace find
  • need work on this

Appendix: Why an Upgrade?

Hejlsberg quote?