Slow is relative. Slow compared to Java? In some cases yes, and in others not so bad: http://benchmarksgame.alioth.debian.org/u64q/compare.php?lan...

Slow compared to, say, Python3? Generally Racket wins out commandingly: http://benchmarksgame.alioth.debian.org/u64q/compare.php?lan...

EDIT: Normal disclaimers about lies, damned lies, and benchmarks apply :-)

I agree. Moreover, like the examples in the benchmargame, usually for code that only crunch numbers Racket is 10x-20x times faster than Python. For code that use a lot of strings or hash-tables, Racket is usually slightly slower, 20%-50%. YMMV.

It's also important to compare the idiomatic version of the code in Racket versus the idiomatic version of the code in Python. If you make a line by line translation, you can get an awful performance.

Also, remember that by default the DrRacket IDE use the mode "debugging" and "preserve stacktrace". They are very handy for debugging but they make the code much slower. The recommendation is to run the benchmarks in the command line. But if you disable "debugging" and "preserve stacktrace" the results are quite good.

“… After all, facts are facts, and although we may quote one to another with a chuckle the words of the Wise Statesman, ‘Lies—damned lies—and statistics,’ still there are some easy figures the simplest must understand, and the astutest cannot wriggle out of.”

Leonard Henry Courtney, 1895.

If people out there are satisfied with Ruby and Python3 performance, then they will be even more satisfied with Racket, which should run at 2x speed at least...