website/content/blog/2024-04-13-sly-repl-io-issues.md

+++ title = "Issue with SBCL console output in Sly" date = 2024-04-13 [taxonomies] tags = ["programming"] categories = ["lisp"] +++

Inconsistent output in REPL

When doing the examples in the Practical Common Lisp book I had confusing output in the repl when prompting the user for CDs using SBCL.

; Dedicated output stream setup (port 46185)
; Redirecting all output to this MREPL
; SLY 1.0.43 (#<MREPL mrepl-1-1>)
CL-USER> (prompt-for-cd)
Title: Unplugged
Eric Clapton 
8
y

Apparently a similar issue was first found on MacOSX and later confirmed on Arch.

The suggestion was given to disable passing the output via a socket to have higher performance that via the protocol by adding

(setf slynk:*use-dedicated-output-stream* nil)

Since I rather have something working that it being high performant not-working I followed the suggestion which fixed the issue:

CL-USER> (prompt-for-cd)
Title: Bar 
Artist: Foo Fighters
Rating: 8
Ripped: y

y (y or n) y
(:TITLE "Bar " :ARTIST "Foo Fighters" :RATING 8 :RIPPED T)
CL-USER>  

so I can continue with the chapter.