main
Matthew Butterick 6 years ago
parent d836e3b958
commit cc60dbbb31

@ -9,37 +9,38 @@
;; todo: generalize these procs so they're not particular to quads
#:mandatory-break-proc [mandatory-break? (const #f)]
#:optional-break-proc [optional-break? (const #f)]
#:size-proc [size-proc (const 1)]
#:group-proc [group-proc values])
#:finish-segment-proc [finish-segment (λ (pieces) (dropf pieces optional-break?))]
#:size-proc [size-proc (const 1)])
((any/c) (integer? any/c
#:break-val any/c
#:mandatory-break-proc procedure?
#:optional-break-proc procedure?
#:size-proc procedure?
#:group-proc procedure?) . ->* . (listof any/c))
#:finish-segment-proc procedure?) . ->* . (listof any/c))
(define start-signal (gensym))
(define last-optional-break-k #f)
(define (capture-optional-break-k!) (let/cc k (set! last-optional-break-k k) #f))
(for/fold ([vals null]
[pieces null]
[size-so-far start-signal]
#:result (reverse (dropf vals optional-break?)))
#:result (reverse (append (finish-segment pieces) vals)))
([x (in-list xs)])
(define-values (size-start size-mid size-end) (size-proc x))
(define at-start? (eq? size-so-far start-signal))
(define underflow? (and (not at-start?) (<= (+ size-so-far size-end) target-size)))
(define (add-to-segment) (values (cons x vals) (if at-start?
size-start
(+ size-so-far size-mid))))
(define (add-to-segment) (values vals (cons x pieces) (if at-start?
size-start
(+ size-so-far size-mid))))
(define (insert-break)
;; when break is found, q is omitted from accumulation
;; and any preceding optional breaks are dropped (that would be trailing before the break)
(values (cons break-val (dropf vals optional-break?)) start-signal))
(values (cons break-val (append (finish-segment pieces) vals)) null start-signal))
(cond
[(mandatory-break? x) (when debug (report x 'got-mandatory-break))
(insert-break)]
[(optional-break? x)
(cond
[at-start? (when debug (report x 'skipping-opt-break-at-beginning)) (values vals size-so-far)]
[at-start? (when debug (report x 'skipping-opt-break-at-beginning)) (values vals null size-so-far)]
[(and underflow? (capture-optional-break-k!)) (when debug (report x 'resuming-breakpoint))
(set! last-optional-break-k #f) ;; prevents continuation loop
(insert-break)]
@ -50,7 +51,8 @@
[last-optional-break-k (when debug (report x 'invoking-last-breakpoint))
(last-optional-break-k #t)]
[else (when debug (report x 'falling-back))
(values (list* x break-val vals) size-start)]))) ;; fallback if no last-breakpoint-k exists
(define-values (vals pcs size-so-far) (insert-break))
(values vals (list x) size-start)]))) ;; fallback if no last-breakpoint-k exists
(define x (q (hasheq 'size (delay (values 1 1 1))) #\x))
@ -61,12 +63,13 @@
(define d (q (hasheq 'size (delay (values 1 1 1))) #\d))
(define sp (q (hasheq 'size (delay (values 0 1 0))) #\space))
(define br (q (hasheq 'size (delay (values 0 0 0))) #\newline))
(define optional-break? (λ (q) (and (quad? q) (memv (car (qe q)) '(#\space)))))
(define (lbs xs size [debug #f])
(insert-breaks xs size debug
#:break-val 'lb
#:mandatory-break-proc (λ (q) (and (quad? q) (memv (car (qe q)) '(#\newline))))
#:optional-break-proc (λ (q) (and (quad? q) (memv (car (qe q)) '(#\space))))
#:optional-break-proc optional-break?
#:size-proc (λ (q) (let ([val (hash-ref (qa q) 'size (λ ()
(if (memv (car (qe q)) '(#\space))
(delay (values 0 1 0))
@ -194,4 +197,29 @@
(check-equal? (pbs (lbs (list x) 1) 2) (list x))
(check-equal? (pbs (lbs (list x x x) 1) 2) (list x 'lb x 'pb x))
(check-equal? (pbs (lbs (list x x x) 2) 2) (list x x 'pb x))
(check-equal? (pbs (lbs (list x x x) 2) 1) (list x 'pb x 'pb x))))
(check-equal? (pbs (lbs (list x x x) 2) 1) (list x 'pb x 'pb x))))
(struct $slug $quad () #:transparent)
(define (slug . xs) ($slug #f xs))
(define (lbs2 xs size [debug #f])
(insert-breaks xs size debug
#:break-val 'lb
#:mandatory-break-proc (λ (q) (and (quad? q) (memv (car (qe q)) '(#\newline))))
#:optional-break-proc optional-break?
#:size-proc (λ (q) (let ([val (hash-ref (qa q) 'size (λ ()
(if (memv (car (qe q)) '(#\space))
(delay (values 0 1 0))
(delay (values 1 1 1)))))])
(if (promise? val) (force val) (val))))
#:finish-segment-proc (λ (pcs) (list ($slug #f (reverse (dropf pcs optional-break?)))))))
(module+ test
(test-case
"mandatory breaks and spurious spaces with slugs"
(check-equal? (lbs2 (list a sp sp sp br b) 2) (list (slug a) 'lb (slug b)))
(check-equal? (lbs2 (list x sp br sp sp x x sp) 3) (list (slug x) 'lb (slug x x)))
(check-equal? (lbs2 (list sp sp x x sp sp br sp sp sp x) 3) (list (slug x x) 'lb (slug x)))
(check-equal? (lbs2 (list a sp b sp sp br sp c) 3) (list (slug a sp b) 'lb (slug c)))
(check-equal? (lbs2 (list x x x x) 3) (list (slug x x x) 'lb (slug x)))
(check-equal? (lbs2 (list x x x sp x x) 2) (list (slug x x) 'lb (slug x) 'lb (slug x x)))
(check-equal? (lbs2 (list x x x sp x x) 3) (list (slug x x x) 'lb (slug x x)))))
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