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(require 'math)
(define (string-append . args)
"join a series of strings"
(if (null? args)
""
(reduce prim-concat args)))
(define (string-length str)
"find the length of a string, not including null"
(do ((len 0 (+ len 1)))
((= (char->integer (string-ref str len)) 0) len)))
(define (substring str start . end)
"Return given substring from start (inclusive) to end (exclusive)."
(let* ((strlen (string-length str))
(end (car-else end strlen))
(len (- end start)))
(when (or (> len strlen) (> end strlen) (> start strlen))
(throw-error "out of string bounds" str start end))
(when (> start end)
(throw-error "invalid substring" start end))
(let ((substr (make-string len #\.)))
(dotimes (i len)
(string-set! substr i (string-ref str (+ i start))))
substr)))
(define (string-map fn str)
"map a function over all characters in a string to produce a new
string"
(let* ((len (string-length str))
(new (make-string len #\space)))
(dotimes (idx len)
(string-set! new idx
(fn (string-ref str idx))))
new))
(define (char-case-switch char uppercase?)
"change the case of char if alpha."
(let* ((ord (char->integer char))
(a (if uppercase?
(char->integer #\a)
(char->integer #\A)))
(z (if uppercase?
(char->integer #\z)
(char->integer #\Z)))
(step (- (char->integer #\A)
(char->integer #\a)))
(step (if uppercase?
step
(- step))))
(if (and (>= ord a)
(<= ord z))
(integer->char (+ ord step))
char)))
(define (char-uppercase char)
"convert an alpha character to uppercase if it isn't
already. ignores non-alpha"
(char-case-switch char #t))
(define (char-lowercase char)
"convert an alpha character to lowercase if it isn't
already. ignores non-alpha"
(char-case-switch char #f))
(define (uppercase str)
"convert a string to uppercase"
(string-map char-uppercase str))
(define (lowercase str)
"convert a string to lowercase"
(string-map char-lowercase str))
(define (string->list str)
"Turn a string into a character list."
(let ((len (string-length str)))
(if (= 0 len)
nil
(do ((idx 0 (+ idx 1))
(result nil (cons (string-ref str idx)
result)))
((= idx len) (reverse result))))))
(define (list->string lst)
"Convert a list-string into a string."
(let* ((len (length lst))
(str (make-string len ".")))
(letrec ((iter (lambda (lst str n)
(if (null? lst)
str
(begin
(string-set! str n (car lst))
(iter (cdr lst) str (+ n 1)))))))
(iter lst str 0))))
(define (string=? . args)
"Return #t if all strings arguments are equal?."
(every-pair? equal? args))
(define (char->string char)
"Return a string containing only char."
(make-string 1 char))
;; String number processing
(define *digits* (list #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9))
(define *digits-16* (list #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
#\a #\b #\c #\d #\e #\f))
(define (digit? ch)
"Return #t if character is a digit."
(member? ch *digits*))
(define (integer-string-list? lst digits)
"Return #t if string-list contains an integer."
(and (every? (rcurry member? digits) (cdr lst))
(or (and (or (eq? (car lst) #\-)
(eq? (car lst) #\+))
(not (null? (cdr lst))))
(member? (car lst) digits))))
(define (integer-string? string)
"Return #t if string contains an integer."
(integer-string-list? (string->list string) *digits*))
(define (string-list->integer lst base)
"Convert the integer in the string-list to an integer."
(letrec ((iter (lambda (number lst)
(if (null? lst)
number
(iter (+ (* base number)
(index-of (curry eq? (car lst)) *digits-16*))
(cdr lst))))))
(cond
((eq? (car lst) #\-) (- (iter 0 (cdr lst))))
((eq? (car lst) #\+) (iter 0 (cdr lst)))
(#t (iter 0 lst)))))
(define (string->integer string (base 10))
"Convert the integer in the string to an integer."
(let ((lst (string->list string)))
(if (not (integer-string-list?
lst (reverse (nthcdr (- 16 base) (reverse *digits-16*)))))
(error "invalid integer in string" string)
(string-list->integer lst base))))
(define (real-string-list? lst)
"Return #t if string-list contains a real."
(letrec ((iter (lambda (lst saw-dot saw-digit)
(cond
((null? lst) (and saw-dot saw-digit))
((eq? (car lst) #\e) (if saw-digit
(integer-string-list?
(cdr lst) *digits*)
#f))
((eq? (car lst) #\.)
(if saw-dot
#f
(iter (cdr lst) #t saw-digit)))
((digit? (car lst)) (iter (cdr lst) saw-dot #t))
(#t #f)))))
(if (or (eq? (car lst) #\-)
(eq? (car lst) #\+))
(iter (cdr lst) #f #f)
(iter lst #f #f))))
(define (real-string? string)
"Return #t if string contains a real."
(real-string-list? (string->list string)))
(define (string-list->real lst)
"Convert real in string-list to real."
(letrec ((iter (lambda (number lst m1 m2 saw-dot)
(cond
((null? lst) number)
((digit? (car lst))
(iter (+ (* m1 number)
(* m2 (index-of (curry eq? (car lst))
*digits*)))
(cdr lst) m1 (if saw-dot (/ m2 10) m2) saw-dot))
((eq? (car lst) #\e)
(* number (expt 10.0 (string-list->integer
(cdr lst) 10))))
((eq? (car lst) #\.)
(iter number (cdr lst) 1.0 0.1 #t))))))
(cond
((eq? (car lst) #\-) (- (iter 0 (cdr lst) 10.0 1.0 #f)))
((eq? (car lst) #\+) (iter 0 (cdr lst) 10.0 1.0 #f))
(#t(iter 0 lst 10.0 1.0 #f)))))
(define (string->real string)
"Convert real in string to real."
(let ((lst (string->list string)))
(if (not (real-string-list? lst))
(error "invalid real in string" string)
(string-list->real lst))))
(define (string-left-pad val char tgt-len)
"pad the left side of string VAL with CHAR until it's TGT-LEN"
(let ((len (string-length val)))
(if (< len tgt-len)
(string-append (make-string (- tgt-len len) char)
val)
val)))
(define (integer->string int (base 10) (pad 0))
"Convert integer into a string, with optional base."
(assert-types (int integer?))
(letrec ((iter (lambda (n lst)
(if (zero? n)
lst
(iter (/ n base)
(cons (list-ref *digits-16* (mod n base)) lst))))))
(if (zero? int)
(string-left-pad "0" #\0 pad)
(string-left-pad (list->string (iter int '())) #\0 pad))))
(define (chomp line)
(let ((len (string-length line)))
(if (eq? (string-ref line (- len 1))
#\newline)
(if (and (> len 1)
(= (char->integer (string-ref line (- len 2)))
13))
(substring line 0 (- len 2))
(substring line 0 (- len 1)))
line)))
(define (trim line)
(let loop ((idx 0))
(let ((char (string-ref line idx)))
(cond
((= (char->integer char) 0)
(list line nil))
((eq? char #\space)
(loop (+ idx 1)))
(else
(substring line idx))))))
(define (string-split line split-char)
(let loop ((idx 0))
(let ((char (string-ref line idx)))
(cond
((= (char->integer char) 0)
(list line nil))
((eq? char split-char)
(list (substring line 0 idx)
(substring line (+ idx 1))))
(else (loop (+ idx 1)))))))
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