49 lines
1.7 KiB
Plaintext
49 lines
1.7 KiB
Plaintext
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'\" Copyright (c) 2008 Donal K. Fellows
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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.TH throw n 8.6 Tcl "Tcl Built-In Commands"
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.so man.macros
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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throw \- Generate a machine-readable error
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.SH SYNOPSIS
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\fBthrow\fI type message\fR
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.BE
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.SH DESCRIPTION
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.PP
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This command causes the current evaluation to be unwound with an error. The
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error created is described by the \fItype\fR and \fImessage\fR arguments:
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\fItype\fR must contain a list of words describing the error in a form that is
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machine-readable (and which will form the error-code part of the result
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dictionary), and \fImessage\fR should contain text that is intended for
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display to a human being.
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.PP
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The stack will be unwound until the error is trapped by a suitable \fBcatch\fR
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or \fBtry\fR command. If it reaches the event loop without being trapped, it
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will be reported through the \fBbgerror\fR mechanism. If it reaches the top
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level of script evaluation in \fBtclsh\fR, it will be printed on the console
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before, in the non-interactive case, causing an exit (the behavior in other
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programs will depend on the details of how Tcl is embedded and used).
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.PP
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By convention, the words in the \fItype\fR argument should go from most
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general to most specific.
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.SH EXAMPLES
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.PP
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The following produces an error that is identical to that produced by
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\fBexpr\fR when trying to divide a value by zero.
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.PP
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.CS
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\fBthrow\fR {ARITH DIVZERO {divide by zero}} {divide by zero}
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.CE
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.SH "SEE ALSO"
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catch(n), error(n), errorCode(n), errorInfo(n), return(n), try(n)
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.SH "KEYWORDS"
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error, exception
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'\" Local Variables:
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'\" mode: nroff
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'\" End:
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