Surely we can’t avoid working on an area of the language just because many community members lack the background expertise to understand the problem? We don’t declare all of FloatingPoint a no-go zone just because Steve is the only person here who understands floats.
The problem is we don’t have a way to express integer values with textual semantics, with an appropriate textual literal syntax, that doesn’t cause additional issues in the rest of the language (i.e., x.isMultiple(of: 'a')). Or more broadly, we don’t have a “safe” and “readable” way to process and generate ASCII bytestrings. I don’t think anyone has lost track of that.
IHDR is just a concrete example of something that is very difficult to safely and efficiently express with existing language tools. If you want a sampling of “pain points”, I would say that any proposed solution must address the following in a safe manner:
// storing a bytestring value
static
var liga:(Int8, Int8, Int8, Int8)
{
return (108, 105, 103, 97) // ('l', 'i', 'g', 'a')
}
// storing an ASCII scalar to mixed utf8-ASCII text
var xml:[UInt8] = ...
xml.append(47) // '/'
xml.append(62) // '>'
// ASCII range operations
let current:UnsafePointer<Int8> = ...
if 97 ... 122 ~= current.pointee // 'a' ... 'z'
{
...
}
// ASCII arithmetic operations
let year:ArraySlice<Int8> = ...
var value:Int = 0
for digit:Int8 in year
{
guard 48 ... 57 ~= digit // '0' ... '9'
else
{
...
}
value = value * 10 + .init(digit - 48) // digit - '0'
}
// reading an ASCII scalar from mixed utf8-ASCII text
let xml:[Int8] = ...
if let i:Int = xml.firstIndex(of: 60) // '<'
{
...
}
// matching ASCII signatures
let c:UnsafePointer<UInt8> = ...
if (c[0], c[1], c[2], c[3]) == (80, 76, 84, 69) // ('P', 'L', 'T', 'E')
{
...
}