New single-letter operators about pip HOT 3 CLOSED

Current ideas:

• U is ++ (Up) and D is -- (Down). The alpha versions are likely to have lower precedence, allowing for expressions like Ux@a instead of ++(x@a).
  • The Unify command is not used much. It should be possible to replace its current functionality with a destructuring assignment syntax: UabcWx -> [abc]:x, which would only cost one byte more and would have the advantage of being an expression rather than a statement.
• E is ** (Exponentiation).
  • The Else branch of an if statement is not used much. The syntax will become EL instead of E.
• Unary M and N could be synonyms for MX and MN, respectively.

This still leaves H unassigned. One idea that comes to mind is Halve. Two objections: 1) Is this a common enough operation to be useful? 2) A Halve operator seems to want a Double operator to keep it company, but D is already spoken for. I suppose Double could be a two-letter operator like DB, though this doesn't save any bytes over just multiplying by 2.

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U, D, and E have been added in the latest commit. The Unify command is gone (destructuring assignments having been added in #8 ), and Else is now EL.

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On further reflection, Halve wasn't useful enough to warrant a single-character operator (it's now HV). Instead, H is a new Prefex operator (mnemonic: Head), and S (repurposed from the old Swap command) is Suffix. These can be used in place of @< and @> in certain situations, though their implementation and operator precedence are a bit different. Swap is now an operator, ::.

from pip.