在Racket REPL中的标识符上加一个“prime”后的奇怪输出

看到了吗 Racketrivia: Using ' as an "identifier suffix" 在诈骗邮件列表上。这个 reply by Robby Findler reply by Matthias Felleisen 两者都解释了这一点。

第一行, x ,正常。

x' ,实际上是一个“表达式和半”。它被解释为一个表达式 十 接着是一个 未完成 表达 ' next-line .

也就是说第三个 实际上被解释为 ' x .

带圆括号的表达式:

> 1 (list 2     ; 1 followed by an unfinished expression
1
> 3 4)          ; finishing it
'(2 3 4)
> 3 4)          ; on its own without the `(list 2` before it it's an error
3
4
; readline-input:13:3: read-syntax: unexpected `)` [,bt for context]

> 1 '                            ; 1 followed by an unfinished expression
1
> (indefatigable inexhaustible)  ; finishes previously unfinished, put after a quote
'(indefatigable inexhaustible)
> (indefatigable inexhaustible)  ; on its own without the quote before it it's an error
; indefatigable: undefined;
;  cannot reference an identifier before its definition
;   in module: top-level
;   internal name: indefatigable