構文
フロントエンドが実装している構文キーワードです。import と define-library 以外はすべて (scheme base) がエクスポートします。この 2 つはプログラムの構文で、どのライブラリもエクスポートしません。delay と delay-force は (scheme lazy) に、cons-stream は Structure and Interpretation of Computer Programs（SICP）互換の名前 に載っています。
| 名前 | 例 | 結果 |
|---|---|---|
quote | (quote (a b c)) | (a b c) |
quasiquote | `(1 ,(+ 1 1) 3) | (1 2 3) |
unquote | `(1 ,(+ 1 1)) | (1 2) |
unquote-splicing | `(1 ,@(list 2 3) 4) | (1 2 3 4) |
lambda | ((lambda (x y) (+ x y)) 3 4) | 7 |
if | (if (> 3 2) 'yes 'no) | yes |
set! | (let ((x 1)) (set! x 2) x) | 2 |
begin | (let ((x 1)) (begin (set! x (* x 10)) (+ x 1))) | 11 |
let | (let ((a 1) (b 2)) (+ a b)) | 3 |
let* | (let* ((a 1) (b (+ a 1))) (list a b)) | (1 2) |
letrec | (letrec ((ev? (lambda (n) (if (= n 0) #t (od? (- n 1))))) (od? (lambda (n) (if (= n 0) #f (ev? (- n 1)))))) (ev? 10)) | #t |
letrec* | (letrec* ((a 1) (b (+ a 1))) (list a b)) | (1 2) |
do | (do ((i 0 (+ i 1)) (sum 0 (+ sum i))) ((= i 5) sum)) | 10 |
cond | (cond ((> 1 2) 'a) ((> 2 1) 'b) (else 'c)) | b |
case | (case (* 2 3) ((2 3 5 7) 'prime) ((1 4 6 8 9) 'composite) (else 'other)) | composite |
and | (and 1 2 'last) | last |
or | (or #f 2 3) | 2 |
when | (when (> 2 1) 'a 'b) | b |
unless | (unless (> 1 2) 'ran) | ran |
define | (let () (define x 2) (* x 3)) | 6 |
define-values | (let () (define-values (q r) (values 17 5)) (list q r)) | (17 5) |
define-record-type | (define-record-type point (make-point x y) point? (x point-x set-point-x!) (y point-y)) | make-point、point?、point-x、set-point-x!、point-y を定義 |
let-values | (let-values (((q r) (values 17 5)) ((s) (values 'x))) (list q r s)) | (17 5 x) |
let*-values | (let*-values (((a b) (values 1 2)) ((c) (values (+ a b)))) (list a b c)) | (1 2 3) |
else | (cond ((> 1 2) 'a) (else 'b)) | b |
=> | (cond ((assv 'b '((a 1) (b 2))) => cadr) (else #f)) | 2 |
guard | (guard (e ((symbol? e) (list 'caught e))) (raise 'oops)) | (caught oops) |
parameterize | (let ((p (make-parameter 1))) (parameterize ((p 2)) (p))) | 2 |
import | (import (scheme base) (scheme write)) | プログラムからその 2 つのライブラリが見える |
define-library | (define-library (counter) (export next!) (import (scheme base)) (begin (define n 0) (define (next!) (set! n (+ n 1)) n))) | (import (counter)) で読めるライブラリ |
include | (include "greet.scm") | include の位置に置かれる greet.scm の定義 |
include-ci | (include-ci "loud.scm") | 同じく、ただし識別子は小文字に畳み込まれる |
cond-expand | (cond-expand (ratios (/ 1 3)) (else 0.33)) | 1/3 |
define-syntax | (let () (define-syntax two (syntax-rules () ((_) 2))) (* (two) 3)) | 6 |
let-syntax | (let-syntax ((double (syntax-rules () ((_ e) (* 2 e))))) (double 21)) | 42 |
letrec-syntax | (letrec-syntax ((my-or (syntax-rules () ((_) #f) ((_ e r ...) (let ((t e)) (if t t (my-or r ...))))))) (my-or #f 7)) | 7 |
syntax-rules | (let-syntax ((first (syntax-rules () ((_ a b ...) 'a)))) (first x y z)) | x |
syntax-error | (one-arg 5) | 5 |
... | (let-syntax ((my-list (syntax-rules () ((_ e ...) (list e ...))))) (my-list 1 2 3)) | (1 2 3) |
_ | (let-syntax ((second (syntax-rules () ((_ _ b . _) b)))) (second 1 2 3)) | 2 |