Wiki: Scheme

• Tips for golfing in Racket / Scheme
• Some tips from the Lisp page can be applied to Scheme.
• printf and format use Lisp format directives. These are very powerful for golfing.

Basic tips

• Use (1+ …) or (1- …) instead of (+ … 1) or (- … 1)
• Symbols can sometimes be used instead of strings: (display'Foo) instead of (display"Foo")
• (unless(…)…) is shorter than (when(not(…))…)
• Use (cdr(command-line)) instead of (command-line-arguments)

do form

do is an iteration construct:

;; Add all numbers between 1 and 10:
(do ((i   1 (1+ i))
     (sum 0 (+ sum i)))
  ((> i 10) sum) ; if i>10: break and return sum (55)

  (display sum)
  (newline))

Looping over a list

There are several ways one can loop over a list, perform some operation, and output the results. Here are a few ways one could print all the arguments to a hole in uppercase:

(do((a(cdr(command-line))(cdr a)))((null? a))(printf"~a~n"(string-upcase(car a))))
(for-each(lambda(a)(printf"~a~n"(string-upcase a)))(cdr(command-line)))
(printf"~{~a~n~}"(map(lambda(a)(string-upcase a))(cdr(command-line))))
(andmap(lambda(a)(printf"~a~n"(string-upcase a)))(cdr(command-line)))
(memp(lambda(a)(printf"~a~n"(string-upcase a))#f)(cdr(command-line)))
(printf"~{~a~n~}"(map string-upcase(cdr(command-line))))
(printf"~:@(~{~a~n~}~)"(cdr(command-line)))

Note that andmap and memp above cannot be replaced by map, as map does not necessarily iterate over its arguments in order.

Splitting a string

The shortest way to split a string on spaces:

(read(open-input-string(format"(~a)"x)))

This yields a list of numbers and symbols, the latter of which can be converted to strings via symbol->string.

2:1 Packer (written in Ruby)

print '(eval(read(open-input-string(utf8->string(string->utf16"',
"(display 10)".encode('utf-8', 'utf-16be'),
'")))))'