pragmas การใช้

The first line is a pragmas turning on warnings and strict mode, which are mandated by fashionable Perl programming style.
The C programming language supports the FMA operation through the fma standard math library function, and standard pragmas controlling optimizations based on FMA.
The Glasgow Haskell Compiler, the most commonly used Haskell compiler, supports pragmas such as {-# INLINE foo #-}.
In some cases, such as some C pragmas, directives are optional compiler hints, and may be ignored, but normally they are prescriptive, and must be followed.
The pragmas, which are tokens that are not part of the syntax but can occur anywhere in the input stream ( e . g . compiler directives or end-of-line characters ).