llvm/flang/documentation/extensions.md

Extensions, deletions, and legacy features supported

• Tabs in source
• <> as synonym for .NE. and /=
• $ and @ as legal characters in names
• .T. and .F.
• Initialization in type declaration statements using /values/
• Kind specification with *, e.g. REAL*4
• DOUBLE COMPLEX
• Signed complex literal constants
• .XOR. as predefined operator (can be overridden)
• .N., .A., .O., .X. predefined operator synonyms
• STRUCTURE, RECORD, UNION, and MAP
• Structure field access with .field
• NCHARACTER type and NC Kanji character literals
• BYTE as synonym for INTEGER(KIND=1)
• Quad precision REAL literals with Q
• X prefix/suffix as synonym for Z on hexadecimal literals
• B, O, Z, and X accepted as suffixes as well as prefixes
• Triplets allowed in array constructors
• Old-style PARAMETER pi=3.14 statement (no parentheses)
• %LOC, %VAL, and %REF
• Leading comma allowed before I/O item list
• Empty parentheses allowed in PROGRAM P()
• Missing parentheses allowed in FUNCTION F
• Cray based POINTER(p,x)
• Arithmetic IF. (Which branch with NaN take?)
• ASSIGN statement, assigned GO TO, and assigned format
• PAUSE statement
• Hollerith literals and edit descriptors
• NAMELIST allowed in the execution part
• Omitted colons on type declaration statements with attributes
• COMPLEX constructor expression, e.g. (x+y,z)
• + and - before all primary expressions, e.g. x*-y
• .NOT. .NOT. accepted
• NAME= as synonym for FILE=
• DISPOSE=
• Data edit descriptors without width or other details
• Backslash escape character sequences in quoted character literals
• D lines in fixed form as comments or debug code
• CONVERT= on the OPEN statement

Extensions and legacy features deliberately not supported

• .LG. as synonym for .NE.
• REDIMENSION
• Allocatable COMMON
• Expressions in formats
• ACCEPT as synonym for READ *
• TYPE as synonym for PRINT
• ARRAY as synonym for DIMENSION
• VIRTUAL as synonym for DIMENSION
• ENCODE and DECODE as synonyms for internal I/O
• IMPLICIT AUTOMATIC, IMPLICIT STATIC
• Default exponent of zero, e.g. 3.14159E
• Characters in defined operators that are neither letters nor digits
• B suffix on unquoted octal constants
• Z prefix on unquoted hexadecimal constants