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diff --git a/source/luametatex/source/utilities/auxarithmetic.h b/source/luametatex/source/utilities/auxarithmetic.h
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+/*
+    See license.txt in the root of this project.
+*/
+
+# ifndef LMT_UTILITIES_ARITHMETIC_H
+# define LMT_UTILITIES_ARITHMETIC_H
+
+/* The |fabs| macro is used in mp. */
+
+/*tex
+
+There has always be much attention on accuracy in \TEX, especially in the perspective of portability. 
+Keep in mind that \TEX\ was written when there was no IEEE floating point defined so all happens in 
+16.16, or actually in 14.16 precission. We could actually consider going 16.16 if we use long integers 
+in some places but it needs some checking first. We could just accept wrapping around as that already
+happens in some places anyway (not all dimension calculation are checked).
+
+In \LUATEX\ and \LUAMETATEX\ we have the \LUA\ engine and that one was exclusively using doubles till 
+5.3 when it went for a more hybrid approach. Because we go a lot between \TEX\ and \LUA\ (in \CONTEXT) 
+that had some consequences and rounding happens all over the place. It is also for that reason that 
+we now use doubles and rounding in some more places in the \TEX\ part: it is more consistent with what 
+happens at the \LUA\ end. And, because IEEE is common now, we are (afaiks) portable enough. 
+
+We don't use round but lround as that one rounds away from zero. In a few places we use llround. Also 
+in some places we clip to the official maxima but not always. 
+
+*/
+
+
+/*
+# undef abs
+# undef fabs
+
+# define abs(x)    ((int)(x) >= 0 ? (int)(x) : (int)-(x))
+# define fabs(x)   ((x) >= 0.0 ? (x) : -(x))
+*/
+
+# define odd(x)    ((x) & 1)
+
+# define lfloor(x) ( (lua_Integer)(floor((double)(x))) )
+# define tfloor(x) ( (size_t)     (floor((double)(x))) )
+# define ifloor(x) ( (int)        (floor((double)(x))) )
+
+//define lround(x) ( ((double) x >= 0.0) ? (lua_Integer) ((double) x + 0.5) : (lua_Integer) ((double) x - 0.5) )
+//define tround(x) ( ((double) x >= 0.0) ? (size_t)      ((double) x + 0.5) : (size_t)      ((double) x - 0.5) )
+//define iround(x) ( ((double) x >= 0.0) ? (int)         ((double) x + 0.5) : (int)         ((double) x - 0.5) )
+//define sround(x) ( ((double) x >= 0.0) ? (int)         ((double) x + 0.5) : (int)         ((double) x - 0.5) )
+
+//define lround(x) ( ((double) x >= 0.0) ? (lua_Integer) ((double) x + 0.5) : (lua_Integer) ((double) x - 0.5) )
+//define tround(x) ( ((double) x >= 0.0) ? (size_t)      ((double) x + 0.5) : (size_t)      ((double) x - 0.5) )
+//define iround(x) ( (int) lround((double) x) )
+
+//define zround(r) ((r>2147483647.0) ? 2147483647 : ((r<-2147483647.0) ? -2147483647 : ((r >= 0.0) ? (int)(r + 0.5) : ((int)(r-0.5)))))
+//define zround(r) ((r>2147483647.0) ? 2147483647 : ((r<-2147483647.0) ? -2147483647 : (int) lround(r)))
+
+# define scaledround(x)  ((scaled) lround((double) x))
+# define longlonground   llround
+# define clippedround(r) ((r>2147483647.0) ? 2147483647 : ((r<-2147483647.0) ? -2147483647 : (int) lround(r)))
+# define glueround(x)    clippedround((double) (x))
+
+# endif