Ashley Davis (Jul 03 2024 at 22:46): Ashley Davis (Jul 03 2024 at 22:46):I ned some help constructing a literal record in Roc.
I'm trying to get up the first test to pass for my new function getNextRecord.
I just want to start with the base case of returning a record/object that indicates there are no items in the next row.
But I'm a bit stumped figuring out how to create a literal record in Roc.
My first guess was that it was going to be something like this:
getNextRow : List GalleryItem, Int U32, Int U32, List GalleryItem, Int U32, List GalleryItem, List Str -> { row : LayoutRow, removedItems: List GalleryItem, remainingItems : List GalleryItem }
getNextRow = \items, galleryWidth, targetRowHeight, currentRowItems, width, removedItems, headings ->
{
row = {
items = [],
galleryWidth = galleryWidth,
targetRowHeight = targetRowHeight,
currentRowItems = currentRowItems,
width = width,
removedItems = removedItems,
headings = headings
},
removedItems = [],
remainingItems = items
}
That didn't work.
I searched through the tutorial and found "record builder syntax" which got me to this:
getNextRow : List GalleryItem, Int U32, Int U32, List GalleryItem, Int U32, List GalleryItem, List Str -> { row : LayoutRow, removedItems: List GalleryItem, remainingItems : List GalleryItem }
getNextRow = \items, galleryWidth, targetRowHeight, currentRowItems, width, removedItems, headings ->
{
row: <- {
items: <- [],
galleryWidth: <- galleryWidth,
targetRowHeight: <- targetRowHeight,
currentRowItems: <- currentRowItems,
width: <- width,
removedItems: <- removedItems,
headings: <- headings
},
removedItems: <- [],
remainingItems: <- items
}
expect getNextRow [] 10 20 [] 0 [] [] == {
row: <- {
items: <- [],
galleryWidth: <- 10,
targetRowHeight: <- 20,
currentRowItems: <- [],
width: <- 0,
removedItems: <- [],
headings: <- []
},
removedItems: <- [],
remainingItems: <- = []
}
I'm not sure what I have wrong here.
Error:
── UNAPPLIED RECORD BUILDER in Layout.roc ──────────────────────────────────────
This record builder was not applied to a function:
23│> {
24│> row: <- {
25│> items: <- [],
26│> galleryWidth: <- galleryWidth,
27│> targetRowHeight: <- targetRowHeight,
28│> currentRowItems: <- currentRowItems,
29│> width: <- width,
30│> removedItems: <- removedItems,
31│> headings: <- headings
32│> },
33│> removedItems: <- [],
34│> remainingItems: <- items
35│> }
However, we need a function to construct the record.
Note: Functions must be applied directly. The pipe operator (|>) cannot be used.
I was hoping to use an anonymous type, but then I thought maybe what I'm doing wrong is that I'm not naming the type.
So I tried naming it:
GetNextRowResult : { row : LayoutRow, removedItems: List GalleryItem, remainingItems : List GalleryItem }
getNextRow : List GalleryItem, Int U32, Int U32, List GalleryItem, Int U32, List GalleryItem, List Str -> GetNextRowResult
getNextRow = \items, galleryWidth, targetRowHeight, currentRowItems, width, removedItems, headings ->
GetNextRowResult {
row: <- {
items: <- [],
galleryWidth: <- galleryWidth,
targetRowHeight: <- targetRowHeight,
currentRowItems: <- currentRowItems,
width: <- width,
removedItems: <- removedItems,
headings: <- headings
},
removedItems: <- [],
remainingItems: <- items
}
expect getNextRow [] 10 20 [] 0 [] [] == GetNextRowResult {
row: <- {
items: <- [],
galleryWidth: <- 10,
targetRowHeight: <- 20,
currentRowItems: <- [],
width: <- 0,
removedItems: <- [],
headings: <- []
},
removedItems: <- [],
remainingItems: <- = []
}
That gets me this error:
── RECORD PARSE PROBLEM in Layout.roc ──────────────────────────────────────────
I am partway through parsing a record, but I got stuck here:
1│ interface Layout
2│ exposes [getNextRow, GalleryItem, LayoutItem, LayoutRow]
3│ imports []
4│
5│ GalleryItem : {
6│ }
7│
8│ LayoutItem : {
9│ }
10│
11│ LayoutRow : {
12│ items : List LayoutItem,
13│ galleryWidth : Int U32,
14│ targetRowHeight : Int U32,
15│ currentRowItems : List GalleryItem,
16│ width : Int U32,
17│ removedItems : List GalleryItem,
18│ headings : List Str
19│ }
20│
21│ GetNextRowResult : { row : LayoutRow, removedItems: List GalleryItem, remainingItems : List GalleryItem }
22│
23│ getNextRow : List GalleryItem, Int U32, Int U32, List GalleryItem, Int U32, List GalleryItem, List Str -> GetNextRowResult
24│ getNextRow = \items, galleryWidth, targetRowHeight, currentRowItems, width, removedItems, headings ->
25│ GetNextRowResult {
26│ row: <- {
27│ items: <- [],
28│ galleryWidth: <- galleryWidth,
29│ targetRowHeight: <- targetRowHeight,
30│ currentRowItems: <- currentRowItems,
31│ width: <- width,
32│ removedItems: <- removedItems,
33│ headings: <- headings
34│ },
35│ removedItems: <- [],
36│ remainingItems: <- items
37│ }
38│
39│ expect getNextRow [] 10 20 [] 0 [] [] == GetNextRowResult {
^
TODO provide more context
I'm not sure what to do now.
Can anyone point me to an example of creating a literal record?
Brendan Hansknecht (Jul 03 2024 at 22:51):They have a : based syntax.
Brendan Hansknecht (Jul 03 2024 at 22:52):Also, that is a really good point that record builder syntax may be a terrible name.
Brendan Hansknecht (Jul 03 2024 at 22:52):That is an advanced feature.
Brendan Hansknecht (Jul 03 2024 at 22:53):Directly porting your example should be this:
getNextRow : List GalleryItem, Int U32, Int U32, List GalleryItem, Int U32, List GalleryItem, List Str -> { row : LayoutRow, removedItems: List GalleryItem, remainingItems : List GalleryItem }
getNextRow = \items, galleryWidth, targetRowHeight, currentRowItems, width, removedItems, headings ->
{
row: {
items: [],
galleryWidth: galleryWidth,
targetRowHeight: targetRowHeight,
currentRowItems: currentRowItems,
width: width,
removedItems: removedItems,
headings: headings
},
removedItems: [],
remainingItems: items
}
Note, you don't need the name: part if the name matches a variable name. So can be shorten to:
getNextRow : List GalleryItem, Int U32, Int U32, List GalleryItem, Int U32, List GalleryItem, List Str -> { row : LayoutRow, removedItems: List GalleryItem, remainingItems : List GalleryItem }
getNextRow = \items, galleryWidth, targetRowHeight, currentRowItems, width, removedItems, headings ->
{
row: {
items: [],
galleryWidth,
targetRowHeight,
currentRowItems,
width,
removedItems,
headings
},
removedItems: [],
remainingItems: items
}
tutorial section on records: https://www.roc-lang.org/tutorial#records
Ashley Davis (Jul 04 2024 at 21:44):That's awesome thank you so much.
Last updated: Jul 26 2025 at 12:14 UTC