plainleaf/website/Space Lua/Quirks.md

A few notable Space Lua quirks.

Lua implementation notes

Space Lua is intended to be a more or less complete implementation of Lua 5.4. However, a few features are (still) missing:

• coroutines (not planned, not useful in the SilverBullet context)
• _ENV (planned)
• Hexadecimal numeric constants with a fractional part, or binary exponents (not supported by JavaScript number parser either)

Conversion of Strings to Numbers

Space Lua converts strings to numbers like standard Lua.

Syntax:

• Leading and trailing whitespace (space, tab, newline, carriage return, form feed and vertical tab) is trimmed.
• The entire string after trimming trailing whitespace must form a number.
• Optional + or - signs are accepted before the number.
• Decimal integers and decimal floats are supported with optional exponent (e.g., 42, -3.5, .5, 5., 1e3, -2.5E-2).
• Hexadecimal integers and hexadecimal floats are also supported:
  • integers (e.g., 0x10, -0XFF),
  • floats require p or P exponent (e.g., 0x1.8p1, -0X10.3P-1).

Failure handling:

• In arithmetic and unary minus expressions invalid strings cause an Lua exception: attempt to perform arithmetic on a non-number.
• tonumber(s) returns nil on failure.
• tonumber(s, base) parses signed integers in bases 2..36 (without decimal points or exponents) and returns nil on invalid input string or base.

Examples (with tonumber function):

Code	Result	Expected
tonumber(' 42 ')	${tonumber(' 42 ')}	42
tonumber('-0xFf ')	${tonumber('-0xFf ')}	-255
tonumber('0x1.8p1')	${tonumber('0x1.8p1')}	3.0
tonumber('1e-2')	${tonumber('1e-2')}	0.01
tonumber('abc')	${tonumber('abc')}	nil
tonumber('1010', 2)	${tonumber('1010', 2)}	10
tonumber(' +fF', 16)	${tonumber(' +fF', 16)}	255
tonumber('8', 8)	${tonumber('8', 8)}	nil

Examples (with arithmetic operations):

Code	Result	Expected
'0xfFfFp1'	${'0xfFfFp1'}	string: 0xfFfFp1
'0xffffP-3' + 0	${'0xffffP-3' + 0}	number: 8191.875
-'123E-12'	${-'123E-12'}	number: -1.23e-10