Function captures

Gleam has a shorthand syntax for creating anonymous functions that take one argument and immediately call another function with that argument: the function capture syntax.

The anonymous function fn(a) { some_function(..., a, ...) } can be written as some_function(..., _, ...), with any number of other arguments passed directly to the inner function. The underscore _ is a placeholder for the argument, equivalent to a in fn(a) { some_function(..., a, ...) }.