CODEWITHSUNDEEP
cluafloating-point
Virus721
Virus721

Reputation: 8315

Lua - Are numbers floats or doubles?

The Lua documentation says that Lua represents values of type number using a double, which allows all long integer values to be correctly represented using a floating point number.

However I see in the code that lua_Number is actually a float. Which is giving me the following warning :

warning C4244: 'argument' : conversion from 'double' to 'lua_Number', possible loss of data

For :

double fVarVal = 0.0;
lua_pushnumber( L, fVarVal );

So how are the values of type number represented in Lua ? float or double ? If they are using floats, can't this create problems when integer values, like array indexes, are being used ?

I'm using Lua 5.3.2 for Windows CE.

Upvotes: 5

Views: 11585

Answers (1)

Nicol Bolas
Nicol Bolas

Reputation: 473447

I'm using Lua 5.3.2 for Windows.

Well that rather changes things. Lua 5.3 added the ability to use actual integers in Lua, directly. Lua always had the lua_pushinteger function, but in 5.3, it doesn't convert it to a double. It is instead a 64-bit integer.

From Lua of course, integers and floats look the same. And most of the Lua C API doesn't make much distinction. But it can if you want it to.

In any case, lua_Number defaults to double, so even on Lua 5.1/2, integers-as-floats was not much of a problem. Of course, lua_Integer and lua_Number can be adjusted as you see fit. Just be aware that external DLLs you use have to be recompiled with those settings too.

Upvotes: 2

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