I feel like JavaScript's arr.flatMap() should have been named:
arr.mapFlat()
because it maps first, then flats.
I often *do* want to flat first then map, and accidentally reach for flatMap() 🤨
arr.mapFlat()
because it maps first, then flats.
I often *do* want to flat first then map, and accidentally reach for flatMap() 🤨
December 11, 2025 at 8:08 PM
I feel like JavaScript's arr.flatMap() should have been named:
arr.mapFlat()
because it maps first, then flats.
I often *do* want to flat first then map, and accidentally reach for flatMap() 🤨
arr.mapFlat()
because it maps first, then flats.
I often *do* want to flat first then map, and accidentally reach for flatMap() 🤨
Advent of code day 2 in Lean
December 3, 2025 at 5:04 AM
Advent of code day 2 in Lean
return customers()
.map(Customer::id)
.flatMap(service::thing
.collectList()
.flatMap(list -> Mono.zi(Mono.just(list, otherThing(format(format, join(delimiter, list.strea().map(Thing::id).toList())).map(tuple ...)
What the fuck is wrong with you?
Why would you nest so many functions?
.map(Customer::id)
.flatMap(service::thing
.collectList()
.flatMap(list -> Mono.zi(Mono.just(list, otherThing(format(format, join(delimiter, list.strea().map(Thing::id).toList())).map(tuple ...)
What the fuck is wrong with you?
Why would you nest so many functions?
November 14, 2024 at 4:48 AM
return customers()
.map(Customer::id)
.flatMap(service::thing
.collectList()
.flatMap(list -> Mono.zi(Mono.just(list, otherThing(format(format, join(delimiter, list.strea().map(Thing::id).toList())).map(tuple ...)
What the fuck is wrong with you?
Why would you nest so many functions?
.map(Customer::id)
.flatMap(service::thing
.collectList()
.flatMap(list -> Mono.zi(Mono.just(list, otherThing(format(format, join(delimiter, list.strea().map(Thing::id).toList())).map(tuple ...)
What the fuck is wrong with you?
Why would you nest so many functions?
Uma coisa besta que me irrita no java hoje em dia: o flatMap só funcionar para streams (e não para Optional).
Você pode transformar com o toStream, mas isso significa que não dá pra usar method reference.
Tô quase retornando Stream ao invés de Optional em alguns métodos.
Você pode transformar com o toStream, mas isso significa que não dá pra usar method reference.
Tô quase retornando Stream ao invés de Optional em alguns métodos.
October 22, 2025 at 3:22 AM
Uma coisa besta que me irrita no java hoje em dia: o flatMap só funcionar para streams (e não para Optional).
Você pode transformar com o toStream, mas isso significa que não dá pra usar method reference.
Tô quase retornando Stream ao invés de Optional em alguns métodos.
Você pode transformar com o toStream, mas isso significa que não dá pra usar method reference.
Tô quase retornando Stream ao invés de Optional em alguns métodos.
flatMap pode ser implementado com recursão apenas
Map to double é só uma funcão 1:1 aplicada em uma lista. Pode ser feita como um reduce (ou recursão, obviamente)
Map to double é só uma funcão 1:1 aplicada em uma lista. Pode ser feita como um reduce (ou recursão, obviamente)
November 7, 2024 at 3:30 AM
flatMap pode ser implementado com recursão apenas
Map to double é só uma funcão 1:1 aplicada em uma lista. Pode ser feita como um reduce (ou recursão, obviamente)
Map to double é só uma funcão 1:1 aplicada em uma lista. Pode ser feita como um reduce (ou recursão, obviamente)
I wrote some code and can't tell if it's wonderful or awful or both.
September 11, 2024 at 8:38 PM
I wrote some code and can't tell if it's wonderful or awful or both.
Can it be expressed as easily as `flatMap` for monads? I have a vague impression that yes, but can you come up with some details?
February 15, 2025 at 6:56 PM
Can it be expressed as easily as `flatMap` for monads? I have a vague impression that yes, but can you come up with some details?
I used flatMap for the first time yesterday, and I’ve been riding that high ever since.
November 2, 2024 at 2:45 PM
I used flatMap for the first time yesterday, and I’ve been riding that high ever since.
Pq filter filtra e map mapeia =P
Poderia tentar fazer ambos ao mesmo tempo? Sim, mas seria um abuso de como fazer esse mapeamento via flatmap da vida, ou um reduce próprio o que na minha visão perde o sentido.
Poderia tentar fazer ambos ao mesmo tempo? Sim, mas seria um abuso de como fazer esse mapeamento via flatmap da vida, ou um reduce próprio o que na minha visão perde o sentido.
April 2, 2025 at 7:12 PM
Pq filter filtra e map mapeia =P
Poderia tentar fazer ambos ao mesmo tempo? Sim, mas seria um abuso de como fazer esse mapeamento via flatmap da vida, ou um reduce próprio o que na minha visão perde o sentido.
Poderia tentar fazer ambos ao mesmo tempo? Sim, mas seria um abuso de como fazer esse mapeamento via flatmap da vida, ou um reduce próprio o que na minha visão perde o sentido.
(>>=) is a monadic let binding so unless you do, flatMap just not the right intuition
March 30, 2025 at 11:51 AM
(>>=) is a monadic let binding so unless you do, flatMap just not the right intuition
I thought compactMap was bad (though worth it to disambiguate flatMap). But then the JavaScript community was like, let's one the fuck up that idea.
https://github.com/tc39/proposal-flatMap/pull/56#issuecomment-371224179
https://github.com/tc39/proposal-flatMap/pull/56#issuecomment-371224179
rename flatten to smoosh by michaelficarra · Pull Request...
As reported in Bugzilla bug 1443630, 8+year old versions ...
github.com
November 22, 2024 at 12:20 PM
I thought compactMap was bad (though worth it to disambiguate flatMap). But then the JavaScript community was like, let's one the fuck up that idea.
https://github.com/tc39/proposal-flatMap/pull/56#issuecomment-371224179
https://github.com/tc39/proposal-flatMap/pull/56#issuecomment-371224179
Array.prototype.reduce gets quite close: The callback's 3rd arg is the index. Return the accumulator and the current value spreaded to flatten.
Eg.
[[1], [2,2], [3,3,3]].reduce((acc, curr, idx) => idx > 1 ? [...acc, ...curr] : acc, [])
I'd argue chaining filter and flatMap is usually clearer tho
Eg.
[[1], [2,2], [3,3,3]].reduce((acc, curr, idx) => idx > 1 ? [...acc, ...curr] : acc, [])
I'd argue chaining filter and flatMap is usually clearer tho
December 28, 2024 at 10:39 PM
Array.prototype.reduce gets quite close: The callback's 3rd arg is the index. Return the accumulator and the current value spreaded to flatten.
Eg.
[[1], [2,2], [3,3,3]].reduce((acc, curr, idx) => idx > 1 ? [...acc, ...curr] : acc, [])
I'd argue chaining filter and flatMap is usually clearer tho
Eg.
[[1], [2,2], [3,3,3]].reduce((acc, curr, idx) => idx > 1 ? [...acc, ...curr] : acc, [])
I'd argue chaining filter and flatMap is usually clearer tho
you could forget map, flatMap, filter and use only fold/reduce. but should you?
May 8, 2025 at 1:06 PM
you could forget map, flatMap, filter and use only fold/reduce. but should you?
just realized flatMap is the same as foo.map().flat() and not foo.flat().map() and now my day is ruined
May 15, 2025 at 12:50 PM
just realized flatMap is the same as foo.map().flat() and not foo.flat().map() and now my day is ruined
Sneak peak at the best mouse 🐁 brain 🧠 networks yet. A whole-cortex flatmap connectivity in factored form, methods and data to be released soon 🧐
November 2, 2024 at 8:37 PM
Sneak peak at the best mouse 🐁 brain 🧠 networks yet. A whole-cortex flatmap connectivity in factored form, methods and data to be released soon 🧐
New major release for #php innmind/black-box:
- Set is now a final class
- adds Set::flatMap() to randomly declare new Sets
- adds PHPUnit 12 support
github.com/Innmind/Blac...
- Set is now a final class
- adds Set::flatMap() to randomly declare new Sets
- adds PHPUnit 12 support
github.com/Innmind/Blac...
Releases · Innmind/BlackBox
Contribute to Innmind/BlackBox development by creating an account on GitHub.
github.com
March 19, 2025 at 7:28 PM
New major release for #php innmind/black-box:
- Set is now a final class
- adds Set::flatMap() to randomly declare new Sets
- adds PHPUnit 12 support
github.com/Innmind/Blac...
- Set is now a final class
- adds Set::flatMap() to randomly declare new Sets
- adds PHPUnit 12 support
github.com/Innmind/Blac...
“JavaScript arrays are getting two new methods: flat() and flatMap(). They return a new array with all sub-array elements smooshed into it.”
🤣🤣🤣 I still wish it was Array.smoosh() https://twitter.com/ChromiumDev/status/1037022478927912961
🤣🤣🤣 I still wish it was Array.smoosh() https://twitter.com/ChromiumDev/status/1037022478927912961
November 18, 2024 at 11:36 PM
“JavaScript arrays are getting two new methods: flat() and flatMap(). They return a new array with all sub-array elements smooshed into it.”
🤣🤣🤣 I still wish it was Array.smoosh() https://twitter.com/ChromiumDev/status/1037022478927912961
🤣🤣🤣 I still wish it was Array.smoosh() https://twitter.com/ChromiumDev/status/1037022478927912961
flatMap is fundamentally a different operation, it just happens to line up with the implementation of bind for non-determinism because flatMapping the continuation over the rhs happens to produce the result you're after
March 30, 2025 at 2:06 PM
flatMap is fundamentally a different operation, it just happens to line up with the implementation of bind for non-determinism because flatMapping the continuation over the rhs happens to produce the result you're after
Rule number 2 - never trust flatMap()
first rule of #ReactiveProgramming - when in doubt - flatMap()
November 22, 2024 at 11:39 PM
Rule number 2 - never trust flatMap()
Isso parece estar menos ligado ao flatmap e mais ligado ao fato dele ter sido chamado em um stream sequencial
April 4, 2025 at 10:07 PM
Isso parece estar menos ligado ao flatmap e mais ligado ao fato dele ter sido chamado em um stream sequencial
Boa, vou continuar minha luta aqui pra aprender certinho. Tava apanhando um pouco pra uns flatMap, minha cabeça ainda tá pensando muito imperativo kk
September 8, 2024 at 1:35 AM
Boa, vou continuar minha luta aqui pra aprender certinho. Tava apanhando um pouco pra uns flatMap, minha cabeça ainda tá pensando muito imperativo kk
Pequenas coisas que me deixam triste, o flatMap do java não lidar com optional. Ter que dar um .stream() tira toda a beleza do que poderia ser referência ao método.
November 29, 2024 at 1:40 PM
Pequenas coisas que me deixam triste, o flatMap do java não lidar com optional. Ter que dar um .stream() tira toda a beleza do que poderia ser referência ao método.
I have to keep reminding myself that flatMap() does map() then flat(), not the other way around.
November 12, 2024 at 3:15 PM
I have to keep reminding myself that flatMap() does map() then flat(), not the other way around.
Programming language agnostic feature request: a compiler error that included the hint, “did you mean flatMap instead of map?”
It would have me days of my life if I added up all the time I’ve spend arriving at that conclusion.
It would have me days of my life if I added up all the time I’ve spend arriving at that conclusion.
June 22, 2023 at 9:39 PM
Programming language agnostic feature request: a compiler error that included the hint, “did you mean flatMap instead of map?”
It would have me days of my life if I added up all the time I’ve spend arriving at that conclusion.
It would have me days of my life if I added up all the time I’ve spend arriving at that conclusion.