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Overview
| Comment: | merge core-8-branch |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | tip-461 |
| Files: | files | file ages | folders |
| SHA3-256: |
d952a4b4eaba5ecb49e57122872410d5 |
| User & Date: | dkf 2019-06-10 20:08:52.137 |
Context
|
2019-06-15
| ||
| 17:49 | TIP 461: text comparison operators for [expr] check-in: 7b13a290cc user: dkf tags: core-8-branch | |
|
2019-06-10
| ||
| 20:08 | merge core-8-branch Closed-Leaf check-in: d952a4b4ea user: dkf tags: tip-461 | |
| 20:02 | merge more expr doc tweaks check-in: 6047e60fec user: dkf tags: core-8-branch | |
| 19:09 | merge 8.7 check-in: b81e8ad1c0 user: dgp tags: tip-461 | |
Changes
Changes to doc/expr.n.
| ︙ | ︙ | |||
93 94 95 96 97 98 99 | \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 | | | 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 |
\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
.SS OPERATORS
.PP
|
| ︙ | ︙ | |||
199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 |
Bit-wise OR. Valid for integer operands.
.TP 20
\fB&&\fR
.
Logical AND. If both operands are true, the result is 1, or 0 otherwise.
This operator evaluates lazily; it only evaluates its second operand if it
must in order to determine its result.
.TP 20
\fB||\fR
.
Logical OR. If both operands are false, the result is 0, or 1 otherwise.
This operator evaluates lazily; it only evaluates its second operand if it
must in order to determine its result.
.TP 20
\fIx \fB?\fI y \fB:\fI z\fR
.
If-then-else, as in C. If \fIx\fR is false , the result is the value of
\fIy\fR. Otherwise the result is the value of \fIz\fR.
This operator evaluates lazily; it evaluates only one of \fIy\fR or \fIz\fR.
.PP
The exponentiation operator promotes types in the same way that the multiply
and divide operators do, and the result is is the same as the result of
\fBpow\fR.
Exponentiation groups right-to-left within a precedence level. Other binary
operators group left-to-right. For example, the value of
.PP
.CS
\fBexpr\fR {4*2 < 7}
.CE
.PP
is 0, while the value of
.PP
| > > > | 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 |
Bit-wise OR. Valid for integer operands.
.TP 20
\fB&&\fR
.
Logical AND. If both operands are true, the result is 1, or 0 otherwise.
This operator evaluates lazily; it only evaluates its second operand if it
must in order to determine its result.
This operator evaluates lazily; it only evaluates its second operand if it
must in order to determine its result.
.TP 20
\fB||\fR
.
Logical OR. If both operands are false, the result is 0, or 1 otherwise.
This operator evaluates lazily; it only evaluates its second operand if it
must in order to determine its result.
.TP 20
\fIx \fB?\fI y \fB:\fI z\fR
.
If-then-else, as in C. If \fIx\fR is false , the result is the value of
\fIy\fR. Otherwise the result is the value of \fIz\fR.
This operator evaluates lazily; it evaluates only one of \fIy\fR or \fIz\fR.
.PP
The exponentiation operator promotes types in the same way that the multiply
and divide operators do, and the result is is the same as the result of
\fBpow\fR.
Exponentiation groups right-to-left within a precedence level. Other binary
operators group left-to-right. For example, the value of
.PP
.PP
.CS
\fBexpr\fR {4*2 < 7}
.CE
.PP
is 0, while the value of
.PP
|
| ︙ | ︙ | |||
348 349 350 351 352 353 354 | substitutions on, enclosing an expression in braces or otherwise quoting it so that it's a static value allows the Tcl compiler to generate bytecode for the expression, resulting in better speed and smaller storage requirements. This also avoids issues that can arise if Tcl is allowed to perform substitution on the value before \fBexpr\fR is called. .PP In the following example, the value of the expression is 11 because the Tcl parser first | | > > > | > | 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 |
substitutions on, enclosing an expression in braces or otherwise quoting it
so that it's a static value allows the Tcl compiler to generate bytecode for
the expression, resulting in better speed and smaller storage requirements.
This also avoids issues that can arise if Tcl is allowed to perform
substitution on the value before \fBexpr\fR is called.
.PP
In the following example, the value of the expression is 11 because the Tcl parser first
substitutes \fB$b\fR and \fBexpr\fR then substitutes \fB$a\fR as part
of evaluating the expression
.QW "$a + 2*4" .
Enclosing the
expression in braces would result in a syntax error as \fB$b\fR does
not evaluate to a numeric value.
.PP
.CS
set a 3
set b {$a + 2}
\fBexpr\fR $b*4
.CE
.PP
|
| ︙ | ︙ |