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x/type/block

Block-form methods: write a callback’s names and body at the call site.

The operative sees the binding list, which is what makes the optional

index possible: the language has no arity introspection.

Class Block

Block-form methods: give a higher-order method a (names …) body … call shape.

(Block %all-syms? xs)

(Block %len>=? xs n)

(Block %name-count xs)

(Block %but-last-n xs n)

(Block %last-n xs n)

(Block %eval-each xs e)

(Block %block-call? args pos n)

(Block %nth xs i)

(Block %take-n xs n)

(Block %drop-n xs n)

(Block %append a b)

(Block %shape-error what n)

(Block %shape-element blk n)

(Block %shape-pair blk n)

(Block %shape-fold blk n)

(Block %shape-binary blk n)

(Block %shape-thunk blk n)

(Block %adapt shape blk n)

(Block %block-fn names body e)

(Block %block-op m shape trailing pos)

(Block %shape-names shape)

(Block %shape-alt shape)

(Block %meta-param-names meta)

(Block %entry-param-names triples)

(Block %join-args names pos seat i)

(Block %block-head class sel static? names pos seat)

(Block %last-cell xs)

(Block %nth-cell xs i)

(Block %pending-entry key)

(Block %notes-have? strs text)

(Block %meta-has-note? meta text)

(Block %doc-note! class sel shape static? pos)

(Block %imethod-of class sel)

(Block method! class sel . opts)

Give a higher-order method a block form: (subject sel (names …) body …).

Shapes: element (default) – (x) or (index x); pair – (p) or (key value);

fold – (acc x) or (acc index x); binary – (a b), no index;

thunk – (), a nullary callback such as a lazy default.

Trailing defaults to 1 for a static method (the subject) and 0 for an

instance method (the receiver is self); fold needs 2 (init, subject).

Position defaults to 0; (List times n f) wraps at 1, the count

ahead of it evaluating in the caller’s env.

The applicative form keeps working unchanged, and (help Class/sel)

still answers from the doc registry.

Do NOT (method-of Class sel) a block-enabled selector: the stored

method is now an operative and a direct call would not evaluate.

Parameters:

• class : CLASS — Class owning the method
• sel : SYMBOL — Selector to give a block form
• opts : LIST — Optional: shape symbol, trailing-argument count, callback position

Returns: ANY — The installed operative

Examples:

(do (Block method! List 'map) (List map (x) (* x 2) (list 1 2))) => (2 4)