loops

Loops as recursive functions

(need to reference termination metrics at some point here)

For and While loops

In ATS2, it is usually encouraged to use recursive functions instead of loops (as it is in most programming languages that allow functional programming). However, there are cases where it may be desirable to have for loops or while loops. For loops in particular are useful for certain parallel programming environments, such as the fork–join model, which is available in ATS2 through OpenMP. However, note that currently OpenMP for loops are only supported by using embedded or external C code due to the difficulty in supporting #pragma omp parallel for in code generation (see the omp_for.dats example).

while loops naturally lend themselves towards waiting for some condition to change, but unlike the use-case mentioned above using for loops, this construct is typically easy to do with recursive functions, so while loops are rarer in ATS2.

Need to copy most info from here https://groups.google.com/forum/#!searchin/ats-lang-users/%22for$20loop%22/ats-lang-users/NfHeSJpaq78/zjys-ug5eMUJ

A simple example

An example using termination metrics

This page discusses briefly several mechanisms for using loops in ATS.

Infinitely recursive functions may be a cause for a segfault. (But sometimes, one may want infinite recursion, as in a main loop; when is it not an issue?) To avoid this possibility, one can take advantage of dependent types and termination metrics, as in this example.

A main loop, useful for creating an application that will keep running until something causes it to return. This can be implemented in several ways.

Firstly,

implement
main () = main() where { ... }