Octal escape sequence decoding in strings does not stop at non-octal digit

Thu, 18 Dec 2025 09:35:53 +0000

Strings suppose to support standard Java escape sequences, including octal escape sequence: [0-7]{1,3}

In Java decoding of octal sequences stop at the first non-octal digit or any other character if there are 1 or two octal digits in the escape sequence. For example:

jshell> "\18"
$1 ==> "\0018"

But Clojure reads up to 3 potentially octal digits greedily resulting in wrongly consuming non-octal digits:

Clojure 1.12.4
user=> "\18"
Syntax error reading source at (REPL:1:5).
Invalid digit: 8

non-octal characters:

Clojure 1.12.4
user=> "\1d"
Syntax error reading source at (REPL:1:5).
Invalid digit: d

And succeed only when there is line terminator or exact three octal digits in supported octal range:

Clojure 1.12.4
user=> "\1"
""
user=> "\1"
""
user=> "\12"
"\n"
user=> "\123"
"S"
user=> "\123d"
"Sd"

Associative destructuring with if-let

Sat, 07 Jun 2025 17:21:45 +0000

Hello,

I'm surprised by the result of this code :

(if-let [{errors :errors} {}]
    errors
    true) => nil

I would have expected the result to be 'true'.

As indicated by the result, 'errors' evaluates to nil, but still it's the 'then' arm of the 'if' that is evaluated.

The guide on destructuring state that "You can utilize destructuring anywhere that there is an explicit or implicit let binding.", so I'm a bit puzzled.

Please, enlighten me. Thanks !

Clojure Q&A - Questions without answers in Syntax and reader

Octal escape sequence decoding in strings does not stop at non-octal digit

Associative destructuring with if-let