diff options
| -rw-r--r-- | usr.bin/bc/bc.1 | 77 |
1 files changed, 61 insertions, 16 deletions
diff --git a/usr.bin/bc/bc.1 b/usr.bin/bc/bc.1 index 3d1bb2f2e48..570e1aedf22 100644 --- a/usr.bin/bc/bc.1 +++ b/usr.bin/bc/bc.1 @@ -1,4 +1,4 @@ -.\" $OpenBSD: bc.1,v 1.13 2003/11/12 19:35:54 jmc Exp $ +.\" $OpenBSD: bc.1,v 1.14 2003/11/17 11:21:00 otto Exp $ .\" .\" Copyright (C) Caldera International Inc. 2001-2002. .\" All rights reserved. @@ -113,12 +113,65 @@ The sequence is ignored within numbers. .Pp Operators -.Bd -unfilled -offset indent -compact -+ \- * / % ^ (`%' is remainder; `^' is power) -++ \-\- (prefix and postfix; apply to names) -== <= >= != < > -= += \-= *= /= %= ^= -.Ed +.Pp +The following arithmetic and logical operators can be used. +The semantics of the operators is the same as in the C language. +They are listed in order of decreasing precedence. +Operators in the same group have the same precedence. +.Bl -column -offset indent "= += \-= *= /= %= ^=" "Associativity" \ +"multiply, divide, modulus" +.It Sy "Operator" Ta Sy "Associativity" Ta Sy "Description" +.It "++ \-\-" Ta "none" Ta "increment, decrement" +.It "\-" Ta "none" Ta "unary minus" +.It "^" Ta "right" Ta "power" +.It "* / %" Ta "left" Ta "multiply, divide, modulus" +.It "+ \-" Ta "left" Ta "plus, minus" +.It "= += -= *= /= %= ^=" Ta "right" Ta "assignment" +.It "== <= >= != < >" Ta "none" Ta "relational" +.It "!" Ta "none" Ta "boolean not" +.It "&&" Ta "left" Ta "boolean and" +.It "||" Ta "left" Ta "boolean or" +.El +.Pp +Note the following: +.Bl -bullet -offset indent +.It +The relational operators may appear in any expression. +The +.St -p1003.2 +standard only allows them in the conditional expression of an +.Sq if , +.Sq while +or +.Sq for +statement. +.It +The relational operators have a lower precedence than the assignment +operators. +This has the consequence that the expression +.Sy a = b < c +is interpreted as +.Sy (a = b) < c , +which is probably not what the programmer intended. +.It +In contrast with the C language, the relational operators all have +the same precedence, and are non-associative. +The expression +.Sy a < b < c +will produce a syntax error. +.It +The boolean operators (!, && and ||) are non-portable extensions. +.It +The boolean not +(!) operator has much lower precedence than the same operator in the +C language. +This has the consquence that the expression +.Sy !a < b +is interpeted as +.Sy !(a < b) . +Prudent programmers use parentheses when writing expressions involving +boolean operators. +.El .Pp Statements .Bd -unfilled -offset indent -compact @@ -272,8 +325,7 @@ option is specified on the command line. .Sh SEE ALSO .Xr dc 1 .Rs -.%B USD -.%V 06 +.%B USD:06 .%A L. L. Cherry .%A R. Morris .%T "BC \- An arbitrary precision desk-calculator language" @@ -305,13 +357,6 @@ The current version of the utility was written by .An Otto Moerbeek . .Sh BUGS -No -.Sq && , -.Sq \(or\(or , -or -.Sq \&! -operators. -.Pp .Ql Quit is interpreted when read, not when executed. .Pp |