You picked the single slowest way to do it. Please see https://gist.github.com/wyager/df063ad4edd9a9c8b0ab762c91a79894 All times are on my Intel Atom Macbook. Compiled with -O3, no other options. Using Lazy Bytestrings (either through the Builder interface or plain old concatenation) is about 7-7.5 times faster than string concatenation so on your computer it should take about 0.12 seconds. In other words, faster than C. This is my usual experience with lazy bytestrings; due to their optimization for cache size, they are extremely fast with almost no effort. They often out-perform "fast" array operations in C due to fusion and cache coherency. I will note that if you want to do exactly what C does (often with only slightly different assembly output), you can often achieve this with unboxed vectors (mutable or immutable, depending on your application). --Will On Mon, Jul 11, 2016 at 10:24 PM, Richard A. O'Keefe <ok@cs.otago.ac.nz> wrote:
Making a list of "Hello world" 10,000,000 times and then concatenating that list to produce a single String took 0.87 seconds (start program to end program) in Haskell.