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exercises(rna-transcription): remove untested RnaError #258

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merged 4 commits into from
Mar 16, 2023
Merged

exercises(rna-transcription): remove untested RnaError #258

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06d93c3
exercises(rna-transcription): remove untested RnaError
ee7 Mar 12, 2023
7e09bd7
Merge branch 'main' into exercises-rna-transcription-remove-RnaError
ee7 Mar 15, 2023
128aee6
Merge branch 'main' into exercises-rna-transcription-remove-RnaError
ee7 Mar 16, 2023
ebab9a1
exercises(rna-transcription): add instructions.append.md
ee7 Mar 16, 2023
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6 changes: 6 additions & 0 deletions exercises/practice/rna-transcription/.docs/instructions.append.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
# Instructions append

## Input validation

This exercise does not require you to validate the input DNA strand.
Each tested input contains only the characters `A`, `C`, `G`, or `T`.
11 changes: 2 additions & 9 deletions exercises/practice/rna-transcription/.meta/example.zig
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Original file line number Diff line number Diff line change
@@ -1,22 +1,15 @@
const std = @import("std");
const mem = std.mem;

pub const RnaError = error{
IllegalDnaNucleotide,
};

pub fn toRna(allocator: mem.Allocator, dna: []const u8) ![]const u8 {
pub fn toRna(allocator: mem.Allocator, dna: []const u8) mem.Allocator.Error![]const u8 {
var rna_slice = try allocator.alloc(u8, dna.len);
for (dna) |dna_nucleotide, i| {
switch (dna_nucleotide) {
'A' => rna_slice[i] = 'U',
'C' => rna_slice[i] = 'G',
'G' => rna_slice[i] = 'C',
'T' => rna_slice[i] = 'A',
else => {
allocator.free(rna_slice);
return RnaError.IllegalDnaNucleotide;
},
else => unreachable,
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I wonder if this (unreachable) might be good to put in a HINTS.md file?

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@ee7 ee7 Mar 15, 2023 •
edited
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Maybe, but unreachable isn't required here. The behavior is just unspecified, in both the instructions and tests.

For example, the user can just return on an unexpected character:

else => return rna_slice,

or skip that character, leaving it undefined:

else => continue,

or set a placeholder character:

else => rna_slice[i] = '_',

For the purposes of an example in this repo, I think unreachable is best - it signals to the maintainer that the behavior is untested.

But yes, I think it's a good idea to add a hint saying that the behavior is unspecified for an unexpected character. I'll do that.

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Done via instructions.append.md: ebab9a1

}
}
return rna_slice;
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2 changes: 1 addition & 1 deletion exercises/practice/rna-transcription/rna_transcription.zig
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@@ -1,6 +1,6 @@
// Import the appropriate standard library and modules

pub fn toRna(allocator: mem.Allocator, dna: []const u8) (RnaError || mem.Allocator.Error)![]const u8 {
pub fn toRna(allocator: mem.Allocator, dna: []const u8) mem.Allocator.Error![]const u8 {
_ = allocator;
_ = dna;
@compileError("please implement the toRna function");
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