update

[zaoqi]

y = x with (foo = 2)

What's it compile to?

[nponeccop]

It's something like

var y = _.clone(x)
y.foo = 2

But only @ptol can answer

[ptol]

@zaoqi It uses cloneObject https://github.com/ptol/oczor/blob/master/libs/std/ff.pre.js and then update foo property.

var y = oc.cloneObject(x)
y.foo = 2

[zaoqi]

It's slow.

[nponeccop]

Yes, we really need a real persistent map (in the sense of https://en.wikipedia.org/wiki/Persistent_data_structure). The current solution is a sort of a compromise between code simplicity, semantics, performance and generating more or less idiomatic js. This means there is no solution that will satisfy all four.

For example, a mutable STRef-based map (in Haskell sense) has a perfect semantics, preformance and it's possible to get idiomatic JS, but it's pretty ugly on Oczor side (and we don't have rank-2 polymorphism either)

[ptol]

@zaoqi Yes, by default for objects Oczor use basic mutable maps from the target language. Other data structure could be used for better performance.