suzanne.soy/fear-of-macros
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Fix hash.refs example. Fixes #15.

Browse Source
This commit is contained in:
Greg Hendershott 2015-04-21 14:31:13 -04:00
parent 2af1256427
commit 27fc80861a
1 changed files with 19 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
index.rkt
View File

@ -1177,17 +1177,16 @@ like JavaScript?
(require (for-syntax racket/syntax))
(define-syntax (hash.refs stx)
(syntax-case stx ()
;; If the optional `default' is missing, assume it's #f.
;; If the optional `default' is missing, use #f.
[(_ chain)
#'(hash.refs chain #f)]
[(_ chain default)
(let ([xs (map (lambda (x)
(datum->syntax stx (string->symbol x)))
(regexp-split #rx"\\."
(symbol->string (syntax->datum #'chain))))])
(with-syntax ([h (car xs)]
[ks (cdr xs)])
#'(hash-refs h 'ks default)))]))
(let* ([chain-str (symbol->string (syntax->datum #'chain))]
[ids (for/list ([str (in-list (regexp-split #rx"\\." chain-str))])
(format-id #'chain "~a" str))])
(with-syntax ([hash-table (car ids)]
[keys (cdr ids)])
#'(hash-refs hash-table 'keys default)))]))
;; Gives us "sugar" to say this:
(hash.refs js.a.b.c)
;; Try finding a key that doesn't exist:
@ -1208,26 +1207,23 @@ messages when used in error. Let's try to do that here.
(syntax-case stx ()
;; Check for no args at all
[(_)
(raise-syntax-error #f "Expected (hash.key0[.key1 ...] [default])"
stx #'chain)]
(raise-syntax-error #f "Expected hash.key0[.key1 ...] [default]" stx #'chain)]
;; If the optional `default' is missing, use #f.
[(_ chain)
#'(hash.refs chain #f)]
[(_ chain default)
;; Check that chain is a symbol, not e.g. a number or string
(unless (symbol? (syntax-e #'chain))
(raise-syntax-error #f "Expected (hash.key0[.key1 ...] [default])"
stx #'chain))
(let ([xs (map (lambda (x)
(datum->syntax stx (string->symbol x)))
(regexp-split #rx"\\."
(symbol->string (syntax->datum #'chain))))])
(raise-syntax-error #f "Expected hash.key0[.key1 ...] [default]" stx #'chain)
(let* ([chain-str (symbol->string (syntax->datum #'chain))]
[ids (for/list ([str (in-list (regexp-split #rx"\\." chain-str))])
(format-id #'chain "~a" str))])
;; Check that we have at least hash.key
(unless (and (>= (length xs) 2)
(not (eq? (syntax-e (cadr xs)) '||)))
(unless (and (>= (length ids) 2)
(not (eq? (syntax-e (cadr ids)) '||)))
(raise-syntax-error #f "Expected hash.key" stx #'chain))
(with-syntax ([h (car xs)]
[ks (cdr xs)])
#'(hash-refs h 'ks default)))]))
(with-syntax ([hash-table (car ids)]
[keys (cdr ids)])
#'(hash-refs hash-table 'keys default)))]))
;; See if we catch each of the misuses
(hash.refs)
(hash.refs 0)