The Machines · Runtime stack

seeddict

A reckoner seed: dict over a list of pairs — machines/seeds/seeddict.shoddy

Summary

seeddict bridges DPUT DGET DHAS DKEYS into the reckoner calculator. A "dict" is a dictionary: values stored under names, called keys. At the keyboard it is an ordinary LIST cell whose elements are PAIR cells — no new stack case. That is the same discipline matrix's seed applies to arrays, applied here to association lists (lists of key-value pairs). "rate" 0.05 PAIR 1 GATHER is a one-entry dict, and DPUT grows it.

Why It's Useful

Not delegated to dict.shoddy's own words, on purpose. DictGet, DictHas and DictPut compare keys with the language's native =. That operator compares a List or a Program cell by identity — are they the same object? — rather than by value. This seed keys by CutEqual instead, the same structural (by-contents) equality = already gives every other stack word. That is what lets "rate" and a computed { 1 2 } key alike behave the way DUP = already promised they would. DGET is also guarded where DictGet isn't. DictGet Errors on a missing key; DGET answers a refusal instead, naming the key.

User's Guide

Let st0 = RckSeedDict(RckNew())
RckEval(st0, Chr(34) & "rate" & Chr(34) & " 0.05 PAIR 1 GATHER")   ' x: one-entry dict
RckEval(st0, Chr(34) & "term" & Chr(34) & " 12 DPUT")               ' x: two-entry dict
RckEval(st0, Chr(34) & "rate" & Chr(34) & " DGET")                  ' x: 0.05

Word Reference

Word	Description
DHAS ( d k -- flag )	Whether the dict has an entry for key k.
DGET ( d k -- v )	The value stored under key k; refuses a missing key, naming it.
DPUT ( d k v -- d )	The dict with key k set to v, added if it was not already there.
DKEYS ( d -- list )	The dict's keys, in the order they were entered.

Who Uses It

	User	How
	halifax	DPUT, DGET, DHAS and DKEYS: a keyed store on the stack, beside the engine's own numbered registers.
	sparky	Sparky folds it too, so a model calling eval reaches the same words halifax puts at a prompt.

A mill claims this seed by folding RckSeedDict over its reckoner state, which is all halifax does.

The Machines It Uses

	Machine	Why
	cuttle	CutEqual keys an association list of CutPair cells structurally, in place of the language's native =.
	reckoner	RckReg, RckSeeding and the argument readers every registered word is built from.
	seq	List plumbing under the LIST-of-PAIR reader every word here shares.