9 – The Complete Syntax of Lua

Question

If I have a variable of string type, I can use the : syntax to call functions on the string metatable:

local s = "%d"
print(s:format(s:byte(1)))  -- 37

但是,这并没有说明字面:

print("%d":format("%d":byte(1)))
--  )  expected near  :

Why? Is there a trick to make this work?

Answer 1

2. 随母体对面字进行回顾:

print(("%d"):format(("%d"):byte(1)))

Answer 2

https://www.lua.org/manual/5.4/manual.html

9 – The Complete Syntax of Lua

...
var ::=  Name | prefixexp ‘[’ exp ‘]’ | prefixexp ‘.’ Name 
...
prefixexp ::= var | functioncall | ‘(’ exp ‘)’
functioncall ::=  prefixexp args | prefixexp ‘:’ Name args
...

Basically:

A "method" functioncall is made of four parts: prefixexp, the colon, the name of the method, and its arguments.
A prefixexp can be either a functioncall itself, an exp wrapped inside parenthesis, or a var.
A var can be an identifier, or its indexed/dotted counterpart.

This effectively disallow using the shorthand :method syntax on all kinds of literal expressions, not just strings. That said, these are all invalid syntax:

nil:has_no_method()
true:or_false()
2:too()
[[long strings]]:same_thing()
function() end:really()
{}:h_yes_definitely()

9 – The Complete Syntax of Lua

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