Re: arithmetic operator precedence

[Peter Stephenson <pws@csr.com>]

"Jun T." wrote:
> I think it would be sufficient to add to the man page something like
> "-3**2 gives 9, not -9, in zsh and many other shells.
> Be sure to use parentheses -(3**2) if you want -9."

That seems a good idea in any case.

Index: Doc/Zsh/arith.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/arith.yo,v
retrieving revision 1.13
diff -u -r1.13 arith.yo
--- Doc/Zsh/arith.yo	12 Jun 2008 13:45:05 -0000	1.13
+++ Doc/Zsh/arith.yo	19 Jun 2008 09:56:13 -0000
@@ -93,8 +93,9 @@
 cindex(operators, arithmetic)
 An arithmetic expression uses nearly the same syntax and
 associativity of expressions as in C.
-The following operators are supported (listed in decreasing order
-of precedence):
+
+In the native mode of operation, the following operators are supported
+(listed in decreasing order of precedence):
 
 startsitem()
 sitem(tt(PLUS() - ! ~ PLUS()PLUS() --))(unary plus/minus, logical NOT, complement, {pre,post}{in,de}crement)
@@ -142,6 +143,10 @@
 sitem(tt(,))(comma operator)
 endsitem()
 
+Note the precedence of exponentiation in both cases is below
+that of unary operators, hence `tt(-3**2)' evaluates as `tt(9)', not
+tt(-9).  Use parentheses where necessary: `tt(-(3**2))'.
+
 cindex(mathematical functions, use of)
 cindex(functions, math, use of)
 Mathematical functions can be called with the syntax

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
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