diff options
Diffstat (limited to 'doc/expr.n')
| -rw-r--r-- | doc/expr.n | 63 |
1 files changed, 45 insertions, 18 deletions
@@ -6,8 +6,6 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: expr.n,v 1.38 2009/05/26 09:08:05 ferrieux Exp $ -'\" .so man.macros .TH expr n 8.5 Tcl "Tcl Built-In Commands" .BS @@ -30,7 +28,7 @@ Expressions almost always yield numeric results For example, the expression .PP .CS -\fBexpr 8.2 + 6\fR +\fBexpr\fR 8.2 + 6 .CE .PP evaluates to 14.2. @@ -41,9 +39,9 @@ additional operators not found in C. .SS OPERANDS .PP A Tcl expression consists of a combination of operands, operators, -and parentheses. +parentheses and commas. White space may be used between the operands and operators and -parentheses; it is ignored by the expression's instructions. +parentheses (or commas); it is ignored by the expression's instructions. Where possible, operands are interpreted as integer values. Integer values may be specified in decimal (the normal case), in binary (if the first two characters of the operand are \fB0b\fR), in octal @@ -70,7 +68,8 @@ Operands may be specified in any of the following ways: .IP [1] As a numeric value, either integer or floating-point. .IP [2] -As a boolean value, using any form understood by \fBstring is boolean\fR. +As a boolean value, using any form understood by \fBstring is\fR +\fBboolean\fR. .IP [3] As a Tcl variable, using standard \fB$\fR notation. The variable's value will be used as the operand. @@ -135,7 +134,20 @@ Multiply, divide, remainder. None of these operators may be applied to string operands, and remainder may be applied only to integers. The remainder will always have the same sign as the divisor and -an absolute value smaller than the divisor. +an absolute value smaller than the absolute value of the divisor. +.RS +.PP +When applied to integers, the division and remainder operators can be +considered to partition the number line into a sequence of equal-sized +adjacent non-overlapping pieces where each piece is the size of the divisor; +the division result identifies which piece the divisor lay within, and the +remainder result identifies where within that piece the divisor lay. A +consequence of this is that the result of +.QW "-57 \fB/\fR 10" +is always -6, and the result of +.QW "-57 \fB%\fR 10" +is always 3. +.RE .TP 20 \fB+\0\0\-\fR . @@ -227,7 +239,7 @@ just as in C, which means that operands are not evaluated if they are not needed to determine the outcome. For example, in the command .PP .CS -\fBexpr {$v ? [a] : [b]}\fR +\fBexpr\fR {$v ? [a] : [b]} .CE .PP only one of @@ -250,19 +262,19 @@ Tcl function in the \fBtcl::mathfunc\fR namespace. The processing of an expression such as: .PP .CS -\fBexpr {sin($x+$y)}\fR +\fBexpr\fR {sin($x+$y)} .CE .PP is the same in every way as the processing of: .PP .CS -\fBexpr {[tcl::mathfunc::sin [expr {$x+$y}]]}\fR +\fBexpr\fR {[tcl::mathfunc::sin [\fBexpr\fR {$x+$y}]]} .CE .PP which in turn is the same as the processing of: .PP .CS -\fBtcl::mathfunc::sin [expr {$x+$y}]\fR +tcl::mathfunc::sin [\fBexpr\fR {$x+$y}] .CE .PP The executor will search for \fBtcl::mathfunc::sin\fR using the usual @@ -271,6 +283,18 @@ rules for resolving functions in namespaces. Either current]::tcl::mathfunc::sin\fR will satisfy the request, and others may as well (depending on the current \fBnamespace path\fR setting). .PP +Some mathematical functions have several arguments, separated by commas like in C. Thus: +.PP +.CS +\fBexpr\fR {hypot($x,$y)} +.CE +.PP +ends up as +.PP +.CS +tcl::mathfunc::hypot $x $y +.CE +.PP See the \fBmathfunc\fR(n) manual page for the math functions that are available by default. .SS "TYPES, OVERFLOW, AND PRECISION" @@ -327,6 +351,7 @@ returns \fB4.0\fR, not \fB4\fR. String values may be used as operands of the comparison operators, although the expression evaluator tries to do comparisons as integer or floating-point when it can, +i.e., when all arguments to the operator allow numeric interpretations, except in the case of the \fBeq\fR and \fBne\fR operators. If one of the operands of a comparison is a string and the other has a numeric value, a canonical string representation of the numeric @@ -337,13 +362,12 @@ is that produced by the \fB%g\fR format specifier of Tcl's \fBformat\fR command. For example, the commands .PP .CS -\fBexpr {"0x03" > "2"}\fR -\fBexpr {"0y" < "0x12"}\fR +\fBexpr\fR {"0x03" > "2"} +\fBexpr\fR {"0y" > "0x12"} .CE .PP both return 1. The first comparison is done using integer -comparison, and the second is done using string comparison after -the second operand is converted to the string \fB18\fR. +comparison, and the second is done using string comparison. Because of Tcl's tendency to treat values as numbers whenever possible, it is not generally a good idea to use operators like \fB==\fR when you really want string comparison and the values of the @@ -360,9 +384,9 @@ once by the Tcl parser and once by the \fBexpr\fR command. For example, the commands .PP .CS -\fBset a 3\fR -\fBset b {$a + 2}\fR -\fBexpr $b*4\fR +set a 3 +set b {$a + 2} +\fBexpr\fR $b*4 .CE .PP return 11, not a multiple of 4. @@ -446,3 +470,6 @@ Copyright (c) 1993 The Regents of the University of California. Copyright (c) 1994-2000 Sun Microsystems Incorporated. Copyright (c) 2005 by Kevin B. Kenny <kennykb@acm.org>. All rights reserved. .fi +'\" Local Variables: +'\" mode: nroff +'\" End: |