# IEEE Standard 754 Special Floating Point Numbers

The following sample code illustrates how special floating point values can be managed in FTN95:

SUBROUTINE SpecialNumber(in, out)
CHARACTER(LEN=*) in
DOUBLE PRECISION out
out = 0.0D0
CALL UPCASE@(in)
SELECT CASE(in)
CASE("MINUS_ZERO")
DCORE8(LOC(out)) = Z'8000000000000000'D
CASE("MINUS_INFINITY")
DCORE8(LOC(out)) = Z'FFF0000000000000'D
CASE("PLUS_INFINITY")
DCORE8(LOC(out)) = Z'7FF0000000000000'D
CASE("NOT_A_NUMBER")
DCORE8(LOC(out)) = Z'FFFFFFFFFFFFFFFF'D
CASE("UNDEFINED")
DCORE8(LOC(out)) = Z'8080808080808080'D
END SELECT
END

LOGICAL FUNCTION IsSpecialNumber(in, val)
CHARACTER(LEN=*) in
DOUBLE PRECISION val
LOGICAL res
res = .FALSE.
CALL UPCASE@(in)
SELECT CASE(in)
CASE("MINUS_ZERO")
res = CORE4(LOC(val)+4)==Z'80000000'.AND.CORE4(LOC(val))==0
CASE("MINUS_INFINITY")
res = CORE4(LOC(val)+4)==Z'FFF00000'.AND.CORE4(LOC(val))==0
CASE("PLUS_INFINITY")
res = CORE4(LOC(val)+4)==Z'7FF00000'.AND.CORE4(LOC(val))==0
CASE("NOT_A_NUMBER")
res = CORE4(LOC(val)+4)==Z'FFFFFFFF'.AND.CORE4(LOC(val))==Z'FFFFFFFF'
CASE("UNDEFINED")
res = CORE4(LOC(val)+4)==Z'80808080'.AND.CORE4(LOC(val))==Z'80808080'
END SELECT
IsSpecialNumber = res
END

PROGRAM test
DOUBLE PRECISION val
LOGICAL IsSpecialNumber
CALL SpecialNumber("MINUS_INFINITY",val)
IF(IsSpecialNumber("MINUS_INFINITY",val)) PRINT*,"OK"
END