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(define-library (csc format)
(export
fprintf
printf
sprintf)
(import (scheme base)
(only (scheme write)
display)
(only (csc loop)
loop)
(only (csc strings)
index
has-prefix?))
(begin
(define (fprintf port format-string . args)
(loop with s = format-string
until (string=? "" s)
if (has-prefix? s "{{")
do (write-string "{" port)
(set! s (string-copy s 2))
else if (has-prefix? s "}}")
do (write-string "}" port)
(set! s (string-copy s 2))
else if (has-prefix? s "{}")
do (display (car args) port)
(set! args (cdr args))
(set! s (string-copy s 2))
else if (or (has-prefix? s "{")
(has-prefix? s "}"))
do (error "invalid format string" format-string)
else
do (let* ((open-brace-pos (index s "{"))
(close-brace-pos (index s "}"))
(format-pos (min open-brace-pos close-brace-pos)))
(when (negative? format-pos)
(set! format-pos (string-length s)))
(write-string s port 0 format-pos)
(set! s (string-copy s format-pos)))))
(define (printf format-string . format-args)
(apply fprintf (current-output-port) format-string format-args))
(define (sprintf format-string . format-args)
(let ((string-builder (open-output-string)))
(apply fprintf string-builder format-string format-args)
(get-output-string string-builder)))))
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