Mercurial > hg > octave-lyh
diff doc/interpreter/expr.txi @ 12627:002948ae5bc0
fix precedence level of transpose operators (bug #32533)
* Makefile.am: Note 16 shift/reduce conflicts in oct-parse.yy.
* lex.ll (BIN_OP_RETURN_INTERNAL, XBIN_OP_RETURN_INTERNAL): New macros.
(BIN_OP_RETURN): Define using BIN_OP_RETURN_INTERNAL.
("--", "++"): Use XBIN_OP_RETURN_INTERNAL to set
lexer_flags.quote_is_transpose to true.
* oct-parse.yy: Set precedence level as documented and for
compatibility with Matlab. Don't set precedence for comma, semicolon
or newline characters.
(UNARY, PLUS_PLUS, MINUS_MINUS, EXPR_NOT): Associativity is now right,
not left.
(oper_expr): New non-terminal. Merge all operator non-terminals
except postfix increment and decrement into oper_expr.
(prefix_expr, binary_expr): Delete unused non-terminals.
* expr.txi: Document precedence to match reality.
* test_parser.m: Fix tests for increment and decrement operators to
match current behavior.
| author | John W. Eaton <jwe@octave.org> |
|---|---|
| date | Thu, 21 Apr 2011 17:41:56 -0400 |
| parents | 99babbf683ff |
| children | 990762e784fe |
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--- a/doc/interpreter/expr.txi +++ b/doc/interpreter/expr.txi @@ -1239,51 +1239,62 @@ any such mistake. When operators of equal precedence are used together, the leftmost -operator groups first, except for the assignment and exponentiation -operators, which group in the opposite order. Thus, the expression -@code{a - b + c} groups as @code{(a - b) + c}, but the expression -@code{a = b = c} groups as @code{a = (b = c)}. +operator groups first, except for the assignment operators, which group +in the opposite order. Thus, the expression @code{a - b + c} groups as +@code{(a - b) + c}, but the expression @code{a = b = c} groups as +@code{a = (b = c)}. The precedence of prefix unary operators is important when another operator follows the operand. For example, @code{-x^2} means @code{-(x^2)}, because @samp{-} has lower precedence than @samp{^}. -Here is a table of the operators in Octave, in order of increasing -precedence. +Here is a table of the operators in Octave, in order of decreasing +precedence. Unless noted, all operators group left to right. @table @code -@item statement separators -@samp{;}, @samp{,}. +@item function call and array indexing, cell array indexing, and structure element indexing +@samp{()} @samp{@{@}} @samp{.} + +@item postfix increment, and postfix decrement +@samp{++} @samp{--} + +These operators group right to left. + +@item transpose and exponentiation +@samp{'} @samp{.'} @samp{^} @samp{**} @samp{.^} @samp{.**} -@item assignment -@samp{=}, @samp{+=}, @samp{-=}, @samp{*=},@samp{/=}. This operator -groups right to left. +@item unary plus, unary minus, prefix increment, prefix decrement, and logical "not" +@samp{+} @samp{-} @samp{++} @samp{--} @samp{~} @samp{!} + +@item multiply and divide +@samp{*} @samp{/} @samp{\} @samp{.\} @samp{.*} @samp{./} -@item logical "or" and "and" -@samp{||}, @samp{&&}. +@item add, subtract +@samp{+} @samp{-} -@item element-wise "or" and "and" -@samp{|}, @samp{&}. +@item colon +@samp{:} @item relational -@samp{<}, @samp{<=}, @samp{==}, @samp{>=}, @samp{>}, @samp{!=}, -@samp{~=}. +@samp{<} @samp{<=} @samp{==} @samp{>=} @samp{>} @samp{!=} +@samp{~=} -@item colon -@samp{:}. +@item element-wise "and" +@samp{&} -@item add, subtract -@samp{+}, @samp{-}. +@item element-wise "or" +@samp{|} -@item multiply, divide -@samp{*}, @samp{/}, @samp{\}, @samp{.\}, @samp{.*}, @samp{./}. +@item logical "and" +@samp{&&} -@item transpose -@samp{'}, @samp{.'} +@item logical "or" +@samp{||} -@item unary plus, minus, increment, decrement, and ``not'' -@samp{+}, @samp{-}, @samp{++}, @samp{--}, @samp{!}, @samp{~}. +@item assignment +@samp{=} @samp{+=} @samp{-=} @samp{*=} @samp{/=} @samp{\=} +@samp{^=} @samp{.*=} @samp{./=} @samp{.\=} @samp{.^=} @samp{|=} +@samp{&=} -@item exponentiation -@samp{^}, @samp{**}, @samp{.^}, @samp{.**}. +These operators group right to left. @end table