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Diffstat (limited to 'contrib/tcl/doc/Eval.3')
| -rw-r--r-- | contrib/tcl/doc/Eval.3 | 98 |
1 files changed, 53 insertions, 45 deletions
diff --git a/contrib/tcl/doc/Eval.3 b/contrib/tcl/doc/Eval.3 index f1a78c80f879e..f10069760f69b 100644 --- a/contrib/tcl/doc/Eval.3 +++ b/contrib/tcl/doc/Eval.3 @@ -1,11 +1,11 @@ '\" '\" Copyright (c) 1989-1993 The Regents of the University of California. -'\" Copyright (c) 1994-1996 Sun Microsystems, Inc. +'\" Copyright (c) 1994-1997 Sun Microsystems, Inc. '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" SCCS: @(#) Eval.3 1.17 96/03/25 20:02:33 +'\" SCCS: @(#) Eval.3 1.21 97/01/22 14:22:03 '\" .so man.macros .TH Tcl_Eval 3 7.0 Tcl "Tcl Library Procedures" @@ -17,9 +17,7 @@ Tcl_Eval, Tcl_VarEval, Tcl_EvalFile, Tcl_GlobalEval \- execute Tcl commands \fB#include <tcl.h>\fR .sp int -.VS \fBTcl_Eval\fR(\fIinterp, cmd\fR) -.VE .sp int \fBTcl_VarEval\fR(\fIinterp, string, string, ... \fB(char *) NULL\fR) @@ -32,8 +30,8 @@ int .SH ARGUMENTS .AS Tcl_Interp **termPtr; .AP Tcl_Interp *interp in -Interpreter in which to execute the command. String result will be -stored in \fIinterp->result\fR. +Interpreter in which to execute the command. +A string result will be stored in \fIinterp->result\fR. .AP char *cmd in Command (or sequence of commands) to execute. Must be in writable memory (\fBTcl_Eval\fR makes temporary modifications to the command). @@ -46,61 +44,71 @@ Name of file containing Tcl command string. .SH DESCRIPTION .PP All four of these procedures execute Tcl commands. -\fBTcl_Eval\fR is the core procedure: it parses commands -from \fIcmd\fR and executes them in -.VS -order until either an error occurs or it reaches the end of the string. -.VE -The return value from \fBTcl_Eval\fR is one -of the Tcl return codes \fBTCL_OK\fR, \fBTCL_ERROR\fR, \fBTCL_RETURN\fR, \fBTCL_BREAK\fR, or +\fBTcl_Eval\fR is the core procedure and is used by all the others. +It executes the commands in the script held by \fIcmd\fR +until either an error occurs or it reaches the end of the script. +.PP +Note that \fBTcl_Eval\fR and \fBTcl_GlobalEval\fR +have been largely replaced by the +object-based procedures \fBTcl_EvalObj\fR and \fBTcl_GlobalEvalObj\fR. +Those object-based procedures evaluate a script held in a Tcl object +instead of a string. +The object argument can retain the bytecode instructions for the script +and so avoid reparsing the script each time it is executed. +\fBTcl_Eval\fR is implemented using \fBTcl_EvalObj\fR +but is slower because it must reparse the script each time +since there is no object to retain the bytecode instructions. +.PP +The return value from \fBTcl_Eval\fR is one of the Tcl return codes +\fBTCL_OK\fR, \fBTCL_ERROR\fR, \fBTCL_RETURN\fR, \fBTCL_BREAK\fR, or \fBTCL_CONTINUE\fR, and \fIinterp->result\fR will point to -a string with additional information (result value or error message). -This return information corresponds to the last command executed from -\fIcmd\fR. +a string with additional information (a result value or error message). +If an error occurs during compilation, this return information +describes the error. +Otherwise, this return information corresponds to the last command +executed from \fIcmd\fR. .PP \fBTcl_VarEval\fR takes any number of string arguments -of any length, concatenates -them into a single string, then calls \fBTcl_Eval\fR to -execute that string as a Tcl command. +of any length, concatenates them into a single string, +then calls \fBTcl_Eval\fR to execute that string as a Tcl command. It returns the result of the command and also modifies -\fIinterp->result\fR in the usual fashion for Tcl commands. The -last argument to \fBTcl_VarEval\fR must be NULL to indicate the end +\fIinterp->result\fR in the usual fashion for Tcl commands. +The last argument to \fBTcl_VarEval\fR must be NULL to indicate the end of arguments. .PP \fBTcl_EvalFile\fR reads the file given by \fIfileName\fR and evaluates its contents as a Tcl command by calling \fBTcl_Eval\fR. It returns -a standard Tcl result that reflects the result of evaluating the -file. +a standard Tcl result that reflects the result of evaluating the file. If the file couldn't be read then a Tcl error is returned to describe why the file couldn't be read. .PP -\fBTcl_GlobalEval\fR is similar to \fBTcl_Eval\fR except that it -processes the command at global level. -This means that the variable context for the command consists of -global variables only (it ignores any Tcl procedure that is active). -This produces an effect similar to the Tcl command ``\fBuplevel 0\fR''. -.PP During the processing of a Tcl command it is legal to make nested -calls to evaluate other commands (this is how conditionals, loops, -and procedures are implemented). -If a code other than -\fBTCL_OK\fR is returned from a nested \fBTcl_Eval\fR invocation, then the -caller should normally return immediately, passing that same -return code back to its caller, and so on until the top-level application is -reached. A few commands, like \fBfor\fR, will check for certain +calls to evaluate other commands (this is how procedures and +some control structures are implemented). +If a code other than \fBTCL_OK\fR is returned +from a nested \fBTcl_Eval\fR invocation, +then the caller should normally return immediately, +passing that same return code back to its caller, +and so on until the top-level application is reached. +A few commands, like \fBfor\fR, will check for certain return codes, like \fBTCL_BREAK\fR and \fBTCL_CONTINUE\fR, and process them specially without returning. .PP -\fBTcl_Eval\fR keeps track of how many nested Tcl_Eval invocations are -in progress for \fIinterp\fR. +\fBTcl_Eval\fR keeps track of how many nested \fBTcl_Eval\fR +invocations are in progress for \fIinterp\fR. If a code of \fBTCL_RETURN\fR, \fBTCL_BREAK\fR, or \fBTCL_CONTINUE\fR is -about to be returned from the topmost \fBTcl_Eval\fR invocation for -\fIinterp\fR, then \fBTcl_Eval\fR converts the return code to \fBTCL_ERROR\fR -and sets \fIinterp->result\fR to point to an error message indicating that +about to be returned from the topmost \fBTcl_Eval\fR +invocation for \fIinterp\fR, +it converts the return code to \fBTCL_ERROR\fR +and sets \fIinterp->result\fR +to point to an error message indicating that the \fBreturn\fR, \fBbreak\fR, or \fBcontinue\fR command was -invoked in an inappropriate place. This means that top-level -applications should never see a return code from \fBTcl_Eval\fR other then -\fBTCL_OK\fR or \fBTCL_ERROR\fR. +invoked in an inappropriate place. +This means that top-level applications should never see a return code +from \fBTcl_Eval\fR other then \fBTCL_OK\fR or \fBTCL_ERROR\fR. + +.SH "SEE ALSO" +Tcl_EvalObj, Tcl_GlobalEvalObj .SH KEYWORDS -command, execute, file, global, interpreter, variable +command, execute, file, global, object, object result, variable |