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| -rw-r--r-- | doc/expr.n | 133 |
1 files changed, 67 insertions, 66 deletions
@@ -17,7 +17,7 @@ expr \- Evaluate an expression .BE .SH DESCRIPTION .PP -The \fIexpr\fR command concatenates \fIarg\fRs, separated by a space, into an expression, and evaluates +Concatenates \fIarg\fRs, separated by a space, into an expression, and evaluates that expression, returning its value. The operators permitted in an expression include a subset of the operators permitted in C expressions. For those operators @@ -37,74 +37,34 @@ operands are specified. Expressions also support non-numeric operands, string comparisons, and some additional operators not found in C. .PP -When an expression evaluates to an integer, the value is the decimal form of -the integer, and when an expression evaluates to a floating-point number, the -value is the form produced by the \fB%g\fR format specifier of Tcl's -\fBformat\fR command. +When the result of expression is an integer, it is in decimal form, and when +the result is a floating-point number, it is in the form produced by the +\fB%g\fR format specifier of \fBformat\fR. .PP .VS "TIP 582" -You can use \fB#\fR at any point in the expression (except inside double -quotes or braces) to start a comment. Comments last to the end of the line or +At any point in the expression except within double quotes or braces, \fB#\fR +is the beginning of a comment, which lasts to the end of the line or the end of the expression, whichever comes first. .VE "TIP 582" .SS OPERANDS .PP An expression consists of a combination of operands, operators, parentheses and commas, possibly with whitespace between any of these elements, which is -ignored. +ignored. Each operand is intepreted as a numeric value if at all possible. .PP -An operand 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\fR -\fBboolean\fR. -.IP [3] -As a variable, using standard \fB$\fR notation. -The value of the variable is then the value of the operand. -.IP [4] -As a string enclosed in double-quotes. -Backslash, variable, and command substitution are performed as described in -\fBTcl\fR. -.IP [5] -As a string enclosed in braces. -The operand is treated as a braced value as described in \fBTcl\fR. -.IP [6] -As a Tcl command enclosed in brackets. -Command substitution is performed as described in \fBTcl\fR. -.IP [7] -As a mathematical function such as \fBsin($x)\fR, whose arguments have any of the above -forms for operands. See \fBMATH FUNCTIONS\fR below for -a discussion of how mathematical functions are handled. -.PP -Because \fBexpr\fR parses and performs substitutions on values that have -already been parsed and substituted by \fBTcl\fR, it is usually best to enclose -expressions in braces to avoid the first round of substitutions by -\fBTcl\fR. -.PP -Below are some examples of simple expressions where the value of \fBa\fR is 3 -and the value of \fBb\fR is 6. The command on the left side of each line -produces the value on the right side. -.PP -.CS -.ta 9c -\fBexpr\fR {3.1 + $a} \fI6.1\fR -\fBexpr\fR {2 + "$a.$b"} \fI5.6\fR -\fBexpr\fR {4*[llength "6 2"]} \fI8\fR -\fBexpr\fR {{word one} < "word $a"} \fI0\fR -.CE -.PP -\fBInteger value\fR +Each operand has one of the following forms: +.RS .PP -An integer operand may be specified in decimal (the normal case, the optional -first two characters are \fB0d\fR), binary -(the first two characters are \fB0b\fR), octal -(the first two characters are \fB0o\fR), or hexadecimal -(the first two characters are \fB0x\fR) form. For +.TP +A \fBnumeric value\fR .PP -\fBFloating-point value\fR +.RS +. +Either integer or floating-point. The first two characters of an integer may +also be \fB0d\fR for decimal, \fB0b\fR for binary, \fB0o\fR for octal or +\fB0x\fR for hexadicimal. .PP -A floating-point number may be specified in any of several +A floating-point number may be take any of several common decimal formats, and may use the decimal point \fB.\fR, \fBe\fR or \fBE\fR for scientific notation, and the sign characters \fB+\fR and \fB\-\fR. The @@ -114,16 +74,9 @@ and \fBNaN\fR, in any combination of case, are also recognized as floating point values. An operand that doesn't have a numeric interpretation must be quoted with either braces or with double quotes. .PP -\fBBoolean value\fR -.PP -A boolean value may be represented by any of the values \fB0\fR, \fBfalse\fR, \fBno\fR, -or \fBoff\fR and any of the values \fB1\fR, \fBtrue\fR, \fByes\fR, or \fBon\fR. -.PP -\fBDigit Separator\fR -.PP Digits in any numeric value may be separated with one or more underscore -characters, "\fB_\fR", to improve readability. These separators may only -appear between digits. The separator may not appear at the start of a +characters, "\fB_\fR". A separator may only +appear between digits, not appear at the start of a numeric value, between the leading 0 and radix specifier, or at the end of a numeric value. Here are some examples: .PP @@ -133,6 +86,54 @@ end of a numeric value. Here are some examples: \fBexpr\fR 0xffff_ffff \fI4294967295\fR \fBformat\fR 0x%x 0b1111_1110_1101_1011 \fI0xfedb\fR .CE +.RE + +.TP +A \fBboolean value\fR +. +Using any form understood by \fBstring is\fR +\fBboolean\fR. +.TP +A \fBvariable\fR +. +Using standard \fB$\fR notation. +The value of the variable is the value of the operand. +.TP +A string enclosed in \fBdouble-quotes\fR +. +Backslash, variable, and command substitution are performed according to the +rules for \fBTcl\fR. +.TP +A string enclosed in \fBbraces\fR. +The operand is treated as a braced value according to the rule for braces in +\fBTcl\fR. +.TP +A Tcl command enclosed in \fBbrackets\fR +. +Command substitution is performed as according to the command substitution rule +for \fBTcl\fR. +.TP +A mathematical function such as \fBsin($x)\fR, whose arguments have any of the above +forms for operands. See \fBMATH FUNCTIONS\fR below for +a discussion of how mathematical functions are handled. +.RE +.PP +Because \fBexpr\fR parses and performs substitutions on values that have +already been parsed and substituted by \fBTcl\fR, it is usually best to enclose +expressions in braces to avoid the first round of substitutions by +\fBTcl\fR. +.PP +Below are some examples of simple expressions where the value of \fBa\fR is 3 +and the value of \fBb\fR is 6. The command on the left side of each line +produces the value on the right side. +.PP +.CS +.ta 9c +\fBexpr\fR {3.1 + $a} \fI6.1\fR +\fBexpr\fR {2 + "$a.$b"} \fI5.6\fR +\fBexpr\fR {4*[llength {6 2}]} \fI8\fR +\fBexpr\fR {{word one} < "word $a"} \fI0\fR +.CE .PP .SS OPERATORS .PP |