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I wouldn't say minilanguages are "liked". Just that C++ iostream is even less liked. And some of the concerns seemed frivolous to me. Why is it a problem that format strings can't validate argument types ahead of time when Lua is a dynamic language?

On 5/26/2017 5:14 PM, François Perrad wrote:
An implementation based on a minilanguage doesn't allow user extension,
for example, you cannot add a "%Q" option to `string.format` in pure Lua.

It isn't because format strings are a minilanguange that makes it unextendable. The current implementation delegates interpretation of format strings to the C runtime. A hypothetical Lua library could parse the format strings itself while being extensible.

That said, an attempt to make the formatting language more Lua-like I think should take cues from LPEG. Use simple composable objects to define the format. A back-of-the-hand example is:

   xy_format = "x = " .. dec() .. " y = " .. dec()
   print(xy_format.format(10, 20))

   pi_format = "pi = " .. fixed(nil, 4)

   dec2 = pad(dec(), 2, "0")
   dec4 = pad(dec(), 4, "0")
   date_format = dec2()/"day".."/"..dec2()/"month".."/"..dec4()/"year"

tom (