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tricks

quick Lua cheat sheet

This is a collection of Lua idioms and tricks that may not be immediately apparent to the casual code reader.

logic
not a == not b both or none
numbers
math.min(math.max(x, min), max) clamp x (upper limit takes precedence)
x ~= x number is NaN
1/0 inf
-1/0 -inf
math.huge == math.huge-1 check if inf is available without dividing by zero
x % 1 fractional part (always positive)
x % 1 == 0 number is integer; math.floor(x) == x
x - x % 1 integer part; but better use math.floor(x)
x - x % 0.01 x floored to two decimal digits
x - x % n closest to x smaller than x multiple of n
math.modf(x) integer part and fractional part
math.floor(x+.5) round
(x >= 0 and 1 or -1) sign
y0 + (x-x0) * ((y1-y0) / (x1 - x0)) linear interpolation
math.fmod(angle, 2*math.pi) normalize an angle
tables
next(t) == nil table is empty
strings
s:match'^something' starts with
s:match'something$' ends with
s:match'["\'](.-)%1' match pairs of single or double quotes
i/o
f:read(4096, '*l') read lines efficiently

Last updated: 4 months ago | Edit on GitHub

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