In a high-level language, the programmer is deprived of the dangerous power to update his own program while it is running. Even more valuable, he has the power to split his machine into a number of separate variables, arrays, files, etc.; when he wishes to update any of these he must quote its name explicitly on the left of the assignment, so that the identity of the part of the machine subject to change is immediately apparent; and, finally, a high-level language can guarantee that all variables are disjoint, and that updating any one of them cannot possibly have any effect on any other.…

For the past few months I’ve been mulling over some things that Russell Johnston made me realize about the relationship between effect systems and coroutines. You can read more of his thoughts on this subject here, but he made me realize that effect systems (like that found in Koka) and coroutines (like Rust’s async functions or generators) are in some ways isomorphic to one another. I’ve been pondering the differences between them, trying to figuring out the advantages and disadvantages of each.…

The idea of a zero cost abstraction is very important to certain programming languages, like Rust and C++, which intend to enable users to write programs with excellent performance profiles with relatively little effort. Since this idea is fundamental to the design of Rust and my work, I want to investigate, for a moment, what exactly a zero cost abstraction even is. The idea is summarized in its original by Bjarne Stroustrup, the original developer of C++:…