Although this is great information I primarily had 'less pure' languages' in mind when I asked. Come to think of it, restricting mutable access to only the rel

Although this is great information I primarily had 'less pure' languages' in mind when I asked. Come to think of it, restricting mutable access to only the relevant objects as per function call using const seems to allow just this! A function having only const input and output "should be" free of side effects (if no global mutables); while still being allowed to run all manner of unpure processes local to its own calling context.