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llvm/flang/documentation/extensions.md
peter klausler 424ec7b35b [flang] Handle empty files gracefully. 
Create interval.h.  Use std::size_t instead of bare size_t.  Redefine parser::Name to not be just a bare string.

Break out and rename CharBlock from token-sequence.h for use in the parse tree.

Incremental replacement of name strings with pointers to cooked characters.

Fix case sensitivity problem.

Use new CharBlock encoding to replace strings for real literal constants.

Normalized cooked character stream to lower case.

Simplify parsing now that cooked stream is lower case.  Replace Keyword in parse tree.

Add static_asserts to || and recovery parsers to enforce same result types.

Remove needless TODO comment inserted earlier.

Fix case conversion on prefixed character literals (f90_correct/dc04.f90).

Use CharBlock in user-state.h.

Complete transition from nextChar to nextCh (i.e., always use pointers).

Document extensions.  Begin work on compiler directive lines.

More documentation work.

Reformat prescan.cc.

More work on compiler directive scanning.

Original-commit: flang-compiler/f18@38d0404e16
Reviewed-on: https://github.com/flang-compiler/f18/pull/29
Tree-same-pre-rewrite: false
2018-03-23 13:32:55 -07:00

2.3 KiB
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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

Extensions and legacy features deliberately not supported

  • .LG. as synonym for .NE.
  • REDIMENSION
  • Allocatable COMMON
  • Expressions in formats
  • ACCEPT as synonym for READ *
  • 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