Notch - Yet Another Scripting Language

Install

macOS / Linux:

curl -fsSL https://notch.cs.montana.edu/install.sh | bash

Windows (PowerShell):

iwr https://notch.cs.montana.edu/install.ps1 | iex

Both scripts download a self-contained build into ~/.notch (macOS/Linux) or %LOCALAPPDATA%\notch (Windows) and add notch to your PATH. Open a new terminal and run:

notch

Uninstall

• macOS / Linux:rm -rf ~/.notch, then remove the # notch PATH line from your shell rc (~/.zshrc, ~/.bashrc, ~/.bash_profile, or ~/.config/fish/config.fish).
• Windows:Remove-Item -Recurse $env:LOCALAPPDATA\notch, then remove the notch entry from your User PATH.

Semantics

The semantics of the language.

Variable, Property, & Invocation Semantics

We deliberated for a long time on what we thought were the proper semantics. We want the language to be easy to iterate on and slow to cause errors. Mistakes should be clear not disappear silently. The approch: variables and calls are strict, property reads coalesce.

An unresolved property read produces the sentinel value <undefined> rather than an error, and once a chain hits <undefined> (or null) every remaining hop short circuits to <undefined>. An unknown variable is still an error, unless you opt out with a trailing ?.

foo # error: unknown variable "foo"
foo? # --> <undefined> -- ? makes the lookup lenient
foo?.bar # --> <undefined>
foo?.bar.baz.bad # --> <undefined> -- the whole chain coalesces

# foo is bound to null
foo # --> null -- a bound null is a value, not an error
foo.bar # --> <undefined>
# foo is bound to an object with a baz() method but no bar
foo.bar # --> <undefined>
foo.bar.baz.bad # --> <undefined>

Invocation is the exception. Calling something that isn't there is almost always a mistake, so it reports with a near match if it exists:

foo.bar() # error: unable to call 'foo.bar', value was null
foo.bar() # error: no method 'bar' on Foo - Did you mean 'baz'?

The ? suffix only relaxes the variable lookup; it does not make a call lenient (foo?.bar() still errors if bar can't be called).

To turn an <undefined> back into a real value, use the fallback operator ?:, and test for it with is undefined:

foo ?: "default" # --> "default"
foo? is undefined # --> true
foo is null # --> true (foo is bound to null)