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Oil Expressions vs. Python

Oil's expression language borrows heavily from Python.

In fact, it literally started with Python's Grammar/Grammar file.

Literal Syntax

• String literals are like shell string literals.
  • Single quoted - raw or c.
  • Double Quoted
  • \u{3bc} instead of \uhhhh and \UHHHHHHHH
• Singleton tuples like 42, are disallowed, in favor of the more explicit tup(42).
• Dicts: come from JavaScript, with unquoted keys, and "punning".
• lists, ints, floats: the same

Additions:

• Lists with unquoted words: %(one two three)

Operators

Oil doesn't overload operators as much:

• a + b is for addition, while a ++ b is for concatenation.
• a < b is only for numbers. cmp() could be for strings.

No "accidentally quadratic"

• No in for array/list membership. Only dict membership.
• The ++= operator on strings doesn't exist

Other:

• I removed the 1:5:2 syntax because 0::2 conflicts with module::name. This might have been unnecessary.
• Egg expressions and ~ rather than the re module.

Semantic Differences

• Iterating over a string yields code points, not one-character strings. s[i] returns an integer code point ("rune").

Significant Newlines

• {} is different than [] and ()

Additions

• d->key

Related Links

• Issue 835: Make expression language compatible with Python