ftor

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At first glance this project seems to be quite similar to sanctuary-def. A summary of the differences between the two libraries would be useful. :)

Gee! I didn't even know this repo. I know Sanctuary, of course. sanctuary-def seems indeed quite similar. How do you manage all these projects? That's incredible!

I have to take a closer look at it. I am curious how you solved particular problems. I am pretty sure we can learn from each other. It seems as if Berlin is becoming a hot-spot for typed Javascript.

Give me a little time to prepare some key points about the differences.

Anyway, nice to hear form you.

I am curious how you solved particular problems.

Likewise!

I am pretty sure we can learn from each other. It seems as if Berlin is becoming a hot-spot for typed Javascript.

Let's exchange ideas. Since we're both in Berlin we could do so in person. Contact me via email if you'd like to get together. :)

Here are far too many key points. This was a piece of work. I didn't intend to write down so many!

I am biased of course - maybe you can check through them and complete things. I guess I store the comparison in a separate file and only link it in the Readme.

TL;DR

sanctuary-def is less strict than ftor but more mature. While sanctuary-def provides good interop (especially with Ramda), ftor is much more radical in its adaptation of Haskell idioms and sacrifices interop for the time being. Sanctuary has a strong focus on type classes and bounded polymorphism, whereas ftor focuses on parametric and row polymorphism along with Hindley-Milner like type unification.

Status

• sdef: stable
• ftor: experimental

Interop

• sdef: Fantasy Land, Ramda
• ftor: none (I'd like to support Static Land but require curried functions)

Polymorphism

• sdef: parametric and bounded polymorphism
• ftor: parametric, rank-2 and row polymorphism

Unification

e.g. is comp(f) immediately unified to the most general type?

• sdef: no
• ftor: yes

Type Hints

e.g. comp(inc) has the intermediate type (a -> Number) -> a -> Number or append([1,2,3]) has the intermediate type [Number] -> [Number]

• sdef: ?
• ftor: yes (accessable via symbol)

Pluggable Runtime Type Checker

• sdef: yes (through ?)
• ftor: yes (through proxy virtualization)

Time of Introspection

• sdef: as soon as argument is supplied
• ftor: as soon as argument is supplied

Currying

• sdef: curried and multi-argument functions
• ftor: only curried functions (pseudo multi-argumet functions are possible, though)

Verbose Error Messages

• sdef: yes
• ftor: yes (bugy though)

Named Intermediate Functions of Curried Function Sequences

e.g. add(2).name // "add"

• sdef: ?
• ftor: yes

Partial Application

• sdef: yes (__ placeholder)
• ftor: no (curried functions only)

Type-Safe ADTs (Sums of Product)

with check of case guarantee

• sdef: ?
• ftor: yes (through Scott encoding)

Records, Tuples

• sdef: yes
• ftor: yes

Homogeneous Array, Map

• sdef: yes
• ftor: yes

Restricted Type Coercion

whenever possible in quirky Javascript...

• sdef: yes
• ftor: yes

Immutability

• sdef: ?
• ftor: no (but restricted mutability, e.g. mutation must not change type)

Duck Typing

In a typed environment you should know your types, so...

• sdef: ?
• ftor: restricted (e.g. 0 in [1,2,3] type checks but "foo" in [1,2,3] throws)

Named Intermediate Functions of Curried Function Sequences

e.g. add(2).name // "add"

sdef: ? ftor: yes

The functions returned by sanctuary-def have inspect and toString methods. For example:

> S.add
add :: FiniteNumber -> FiniteNumber -> FiniteNumber

The same applies to the result of partially applying one of these functions. For example:

> S.add (2)
add(2) :: FiniteNumber -> FiniteNumber

The functions are anonymous in both cases.

@davidchambers I had a short discussion with Aadit, who has been working on a Hindley-Milner type checker for quite some time and according to him ftor is a type validator (as opposed to a tpye checker), because it assumes correct types for given implementations, instead of inferring them. I think this applies to Sanctuary as well.

It's good to know the correct terminology. The term type checking may be used more broadly in the programming community than its formal definition permits. ;)