Scheme Output/String Formatting Best Practices

What is your preference? Are there other alternatives possible by composing R7RS base library procedures and macros?

; R7RS compliant version
(import (scheme write))
(define world "World)
(for-each display `("Hello, " ,world "!\n")

; R7RS with SRFI 28/29/48 for formatted string templates
(import (scheme write)
(srfi 28))
(define world "World)
(display (format "Hello, ~a!\n" world))

R7RS is bloated garbage and I refuse to have anything to do with it.

Symta:
World = \World
say "Hello, [World]!"

Common Lisp:
(! world = "World"
! "Hello, {world}!")

ONE WORD. THE FORCED EXCLAMATIONIFICATION OF THE CODE. THREAD OVER

>>4
Is that a reader extension? Looks like shit.

>>6

no. it is a defmacro

>>2
You are thinking of R6RS. R7RS isn't bloated.

I just wrote the following macro and helper procedures for logging text to the terminal and log file, or to an explicit file, for use in my autoconf library.

Portable R7RS doesn't seem to have built in way to append to an output file, so I had to copy the contents of the file first into a list of lines, then I output those lines before appending the new message. Thoughts for improvement?

(define log-file #f) ; this gets initialized later

(define (with-output-to-log-file thunk)
(thunk)
(if (output-port? log-file)
(parameterize ((current-output-port log-file))
(thunk)
(flush-output-port))))

(define (with-output-to-file/append file thunk)
(let ((lines '()))
(if (file-exists? file)
(with-input-from-file file
(lambda ()
(do ((line (read-line) (read-line)))
((eof-object? line))
(set! lines (cons line lines))))))
(with-output-to-file file
(lambda ()
(for-each (lambda (x) (write-string x) (newline)) (reverse lines))
(thunk)))))

(define-syntax ac-echo
(syntax-rules (> >>)
((_ >> file args ...) (with-output-to-file/append file (lambda () (for-each display '(args ...)))))
((_ > file args ...) (with-output-to-file file (lambda () (for-each display '(args ...)))))
((_ args ...) (with-output-to-log-file (lambda () (for-each display '(args ...)))))))

;; Examples

(define you "/prog/")

(ac-echo "Hello, " you "!\n") ; prints "Hello, /prog/!" to the terminal and to the current log file if any
(ac-echo > "out.txt" "Hello, " you "!\n") ; writes "Hello, /prog/!" to the file named "out.txt"
(ac-echo >> "out.txt" "Hello, " you "!\n") ; appends "Hello, /prog/!" to the file named "out.txt"

Formatting was ruined at end. Should be:

(define you "[spoiler]/prog/[/spoiler]")

(ac-echo "Hello, " you "!\n") ; prints "Hello, [spoiler]/prog/[/spoiler]!" to the terminal and to the current log file if any
(ac-echo > "out.txt" "Hello, " you "!\n") ; writes "Hello, [spoiler]/prog/[/spoiler]!" to the file named "out.txt"
(ac-echo >> "out.txt" "Hello, " you "!\n") ; appends "Hello, [spoiler]/prog/[/spoiler]!" to the file named "out.txt"

Get this through those thick skulls of yours: THERE ARE NO BEST PRACTICES!!! There are only unsuitable ones, good ones, and better ones for the particular situation at hand, and being able to consider the tradeoffs between all possible solutions is the skill that any engineering is about. Attempting to distill the decisionmaking process of a whole discipline into a set of "best practices" to be followed religiously and brainlessly like trained monkeys is pure idiocy.

>>11
Thanks for the advice. And nice dubs.

EXPERT PRINT

(import (scheme base)
(scheme process-context)
(scheme write))

(define (terminal-port? port) #t)

(define *color-terminal-supported*
(let-syntax ((color-term? (syntax-rules () ((_ t names ...) (or (string=? t names) ...)))))
(let ((term (get-environment-variable "TERM")))
(if (string? term)
(color-term? term "xterm" "xterm-16color" "xterm-88color" "xterm-256color"
"rxvt" "rxvt-16color" "konsole" "konsole-16color")
#f))))

(define *color-text-enabled* #t)

(define (color-terminal-supported?)
*color-terminal-supported*)

(define (color-terminal-port? port)
(and *color-text-enabled*
*color-terminal-supported*
(terminal-port? port)))

(define (use-color-text?)
*color-text-enabled*)

(define (use-color-text value)
(set! *color-text-enabled* value))

(define-record-type <ansi-tty-code>
(make-ansi-tty-code code)
ansi-tty-code?
(code ansi-tty-code->string))

(define (print-ansi-tty-tokens port-or-ports tokens)
(let loop ((ports port-or-ports))
(unless (null? ports)
(let ((p (if (list? ports) (car ports) ports)))
(cond
((color-terminal-port? p)
(for-each
(lambda (t)
(if (ansi-tty-code? t)
(write-string (ansi-tty-code->string t) p)
(display t p)))
tokens)
(write-string "\x1B[0m" p))
(else
(for-each
(lambda (t)
(unless (ansi-tty-code? t)
(display t p)))
tokens))))
(when (list? port-or-ports)
(loop (cdr port-or-ports))))))

(define-syntax make-ansi-tty-command-token
(syntax-rules ()
((_ commands ...)
(begin (make-ansi-tty-code (string-append "\x1B[0" commands ... "m"))))))

(define-syntax define-print-syntax
(syntax-rules ()
((_ (name print-tokens) ((make-command-token) (command-name command-data) ...))
(begin
(define-syntax command-transformer
(syntax-rules (command-name ...)
((command-transformer ports (tokens (... ...)) ())
(print-tokens ports `(,tokens (... ...))))
((command-transformer ports (tokens (... ...)) (commands (... ...)) command-name expr (... ...))
(command-transformer ports (tokens (... ...)) (commands (... ...) command-data) expr (... ...))) ...
((command-transformer ports (tokens (... ...)) () x expr (... ...))
(command-transformer ports (tokens (... ...) x) () expr (... ...)))
((command-transformer ports (tokens (... ...)) (commands (... ...)) x expr (... ...))
(command-transformer ports (tokens (... ...) (make-command-token commands (... ...))) () x expr (... ...)))))
(define-syntax name
(syntax-rules ()
((name ports expressions (... ...))
(command-transformer ports () () expressions (... ...)))))))))

(define-print-syntax (print-ansi-tty print-ansi-tty-tokens)
((make-ansi-tty-command-token)
(:normal ";0")
(:bold ";1")
(:faint ";2")
(:italic ";3")
(:underline ";4")
(:blink ";5")
(:strikethrough ";9")
(:black ";30")
(:red ";31")
(:green ";32")
(:yellow ";33")
(:blue ";34")
(:magenta ";35")
(:cyan ";36")
(:white ";37")
(:black-bg ";40")
(:red-bg ";41")
(:green-bg ";42")
(:yellow-bg ";43")
(:blue-bg ";44")
(:magenta-bg ";45")
(:cyan-bg ";46")
(:white-bg ";47")))

(define (expert-print text)
(let ((port (current-output-port)))
(let loop ((i 0) (n (string-length text)))
(unless (>= i n)
(print-ansi-tty port :bold :underline :magenta " " :normal " ")
(loop (+ i 2) n)))
(newline port)
(let loop ((i 0) (n (string-length text)))
(unless (>= i n)
(if (= (modulo i 2) 0)
(print-ansi-tty port :bold :italic :magenta (string-ref text i))
(print-ansi-tty port :bold :italic :underline :cyan (string-ref text i)))
(loop (+ i 1) n)))
(newline port)))

(expert-print "EXPERT PROGRAMMER")
(newline)

NO EXCEPTIONS!

>>13
mmmmmm~ I am sure that with such a great code you have a really nice anus!

>>14
go back to /lgbt/

>>15

/lgbt/

And you back to 4chan :)

>>13
Defining a macro and using it only once eh? You're having too much fun.

>>14

Mine is better!

>>17
Macros have other uses too, such as reducing code-duplication, increasing expressivity--even in one-off instances.

>>19

even in one-off instances.

This is the reason LITHP is shit - languages extended with arbitratry, unstandardized shit are unreadable by anyone except their author.

>>20

unreadable by anyone except their author.

Nobody cares about anyone.

http://www.paulgraham.com/avg.html

Lisp is a genuinely good (as in superior) language and this ``LITHP'' idiot is just a troll and new. It and C really are the best of bunch.

best of the bunch*

>>21
That's the whole point. Programming is a social activity and LITHPers are forever bound to be uncommunicative loners comforting themselves with the "I'm lone wolf genius above the averages" myth.

>>22

It and C really are the best of bunch.

You're clearly either an idiot or a troll. Though the dubs are nice.

Also Paul Graham's site died along with his "Arc" crap.

>>25

Leah Culver milked the last money out of him. He is now too busy writing Java himself for a hobby project.

BTW, why there is no real code in Leah's repo, besides forks and social crap?
https://github.com/leah/getwelltermie

I don't understand this leah maymay. Is it because of her funny name?

>>28

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>>29
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>>30

Will you give me pics of your butthole if I do it?

>>30

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>>34

Shalom!

i am a heroin. i'm in a plastic bag and i shoot into veins of the blood w/ a needle. if you dont repost this comment on 10 other pages i will fly into your syringe tonight and give you a really good time

>>36
Heroin comes in balloons. Remember how that whore in Pulp Fiction stole Vincent's junk thinking it was coke and overdosed? That's because the dealer put it in a baggy because he was out of balloons when he sold it to him.