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Implement List.find

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`List.find : List elem, (elem -> Bool) -> Result elem [ NotFound ]*`
behaves as follows:

```
>>> List.find [1, 2, 3] (\n -> n > 2)
Ok 2
>>> List.find [1, 2, 3] (\n -> n > 4)
Err NotFound
```

We implement this as builtin in two phases. First, we call out to a
pure-llvm-lowlevel `ListFindUnsafe` that returns a record indicating
whether a satisfying element was found, and the value of that element
(the value is all null bytes if the element wasn't found). Then, we lift
that record to a `Result` via a standard construction of the can AST.

Closes #1909
This commit is contained in:
ayazhafiz 2021-11-07 20:56:46 -05:00
parent 35df58c18f
commit f65b174ab5
16 changed files with 417 additions and 8 deletions
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43
compiler/gen_llvm/src/llvm/build.rs
View file

@ -9,10 +9,10 @@ use crate::llvm::build_dict::{
use crate::llvm::build_hash::generic_hash;
use crate::llvm::build_list::{
self, allocate_list, empty_list, empty_polymorphic_list, list_any, list_append, list_concat,
list_contains, list_drop, list_drop_at, list_get_unsafe, list_join, list_keep_errs,
list_keep_if, list_keep_oks, list_len, list_map, list_map2, list_map3, list_map4,
list_map_with_index, list_prepend, list_range, list_repeat, list_reverse, list_set,
list_single, list_sort_with, list_swap, list_take_first,
list_contains, list_drop, list_drop_at, list_find_trivial_not_found, list_find_unsafe,
list_get_unsafe, list_join, list_keep_errs, list_keep_if, list_keep_oks, list_len, list_map,
list_map2, list_map3, list_map4, list_map_with_index, list_prepend, list_range, list_repeat,
list_reverse, list_set, list_single, list_sort_with, list_swap, list_take_first,
};
use crate::llvm::build_str::{
empty_str, str_concat, str_count_graphemes, str_ends_with, str_from_float, str_from_int,
@ -4887,6 +4887,37 @@ fn run_higher_order_low_level<'a, 'ctx, 'env>(
_ => unreachable!("invalid list layout"),
}
}
ListFindUnsafe { xs } => {
let (list, list_layout) = load_symbol_and_layout(scope, &xs);
let (function, closure, closure_layout) = function_details!();
match list_layout {
Layout::Builtin(Builtin::EmptyList) => {
// Returns { found: False, elem: \empty }, where the `elem` field is zero-sized.
// NB: currently we never hit this case, since the only caller of this
// lowlevel, namely List.find, will fail during monomorphization when there is no
// concrete list element type. This is because List.find returns a
// `Result elem [ NotFound ]*`, and we can't figure out the size of that if
// `elem` is not concrete.
list_find_trivial_not_found(env)
}
Layout::Builtin(Builtin::List(element_layout)) => {
let argument_layouts = &[**element_layout];
let roc_function_call = roc_function_call(
env,
layout_ids,
function,
closure,
closure_layout,
function_owns_closure_data,
argument_layouts,
);
list_find_unsafe(env, layout_ids, roc_function_call, list, element_layout)
}
_ => unreachable!("invalid list layout"),
}
}
DictWalk { xs, state } => {
let (dict, dict_layout) = load_symbol_and_layout(scope, &xs);
let (default, default_layout) = load_symbol_and_layout(scope, &state);
@ -5757,7 +5788,9 @@ fn run_low_level<'a, 'ctx, 'env>(
ListMap | ListMap2 | ListMap3 | ListMap4 | ListMapWithIndex | ListKeepIf | ListWalk
| ListWalkUntil | ListWalkBackwards | ListKeepOks | ListKeepErrs | ListSortWith
| ListAny | DictWalk => unreachable!("these are higher order, and are handled elsewhere"),
| ListAny | ListFindUnsafe | DictWalk => {
unreachable!("these are higher order, and are handled elsewhere")
}
}
}