string comparison Case-Insensitive ?

ruby

compiling original lua is the most easy thing.

using tcc:
del luac.c
tcc *.c

using mingw gcc:
del luac.c
gcc *.c

using msvs:
cl *.c

and then a .exe is generated! super easy.

just wish luart is also such easy. no make file , just compile every source file

usually a is bigger than A, but in luart A is bigger.
and it is case insensitive.
why?

► print(_VERSION)
LuaRT 2.1.0

► 'a'>'A'
false

► a={'assert', 'Base', 'car'} table.sort(a) print(table.concat(a, ' '))
assert Base car

if it is case sensitive , I can easily use string.lower() function to compare strings case insensitively,

if it is insensitive now, how to compare strings case sensitive? not that easy

Samir

Interesting !

Might be related to how LuaRT uses UTF8 strings but very unsure of that...
Certainly because QuickRT uses raw console.readchar() for line input. Try in a LuaRT script it might give the same result than in Lua

ruby

no. luart gave same result as quickrt.

echo print('a'^>'A') > test.lua

type test.lua
print('a'>'A')

luart test.lua
false

lua.exe test.lua
true

Samir

I will investigate this thank you Ruby

ruby

I think I have found the answer.

by default, in original lua, locale is C.
lua.exe -e "print(os.setlocale())"
C

and in luart, locale is local system.

locale changes many things.

in luart I can change it back:

print('a' > 'A')
print('after set locale to c: ')
os.setlocale('C')
print('a' > 'A')

false
after set locale to c:
true

Samir

Very strange, strcmp() (the underlying C function that do the string comparaison in Lua) is not locale dependent in the specifications...

Samir

You are right, the locale impacts the result of strcmp(), I have tested using the LuaRT C FFI, you can use strcoll() or a different locale to compare strings with correct results :

local c = require "c"

-- use the C runtime library
local ucrt = c.Library()

-- prototype of the  C functions used to compare strings
ucrt.strcoll = "(ZZ)i" -- Compare strings using locale
ucrt.strcmp = "(ZZ)i" -- Compare strings

local arg1 = "a"
local arg2 = "A"

print(ucrt.strcoll(arg1, arg2)) -- returns -1 => arg1 < arg2
print(ucrt.strcmp(arg1, arg2)) -- returns 1 => arg1 > arg2

ruby

first assign a string to it, strcoll = "(ZZ)i",
and then call it like a function? it's really hard to understand such FFI magic, though powerful

Samir

Yes true magic 😉
Here is the documentation for this strange letters [Login to see the link]