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- '\" $Header: /user6/ouster/tcl/man/RCS/ExprLong.3,v 1.11 93/04/17 15:31:16 ouster Exp $ SPRITE (Berkeley)
- '\"
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- .HS Tcl_ExprLong tclc 7.0
- .BS
- .SH NAME
- Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBool, Tcl_ExprString \- evaluate an expression
- .SH SYNOPSIS
- .nf
- \fB#include <tcl.h>\fR
- .sp
- int
- \fBTcl_ExprLong\fR(\fIinterp, string, longPtr\fR)
- .sp
- int
- \fBTcl_ExprDouble\fR(\fIinterp, string, doublePtr\fR)
- .sp
- int
- \fBTcl_ExprBoolean\fR(\fIinterp, string, booleanPtr\fR)
- .sp
- int
- \fBTcl_ExprString\fR(\fIinterp, string\fR)
- .SH ARGUMENTS
- .AS Tcl_Interp *booleanPtr
- .AP Tcl_Interp *interp in
- Interpreter in whose context to evaluate \fIstring\fR.
- .AP char *string in
- Expression to be evaluated. Must be in writable memory (the expression
- parser makes temporary modifications to the string during parsing, which
- it undoes before returning).
- .AP long *longPtr out
- Pointer to location in which to store the integer value of the
- expression.
- .AP int *doublePtr out
- Pointer to location in which to store the floating-point value of the
- expression.
- .AP int *booleanPtr out
- Pointer to location in which to store the 0/1 boolean value of the
- expression.
- .BE
-
- .SH DESCRIPTION
- .PP
- These four procedures all evaluate an expression, returning
- the result in one of four different forms.
- The expression is given by the \fIstring\fR argument, and it
- can have any of the forms accepted by the \fBexpr\fR command.
- The \fIinterp\fR argument refers to an interpreter used to
- evaluate the expression (e.g. for variables and nested Tcl
- commands) and to return error information. \fIInterp->result\fR
- is assumed to be initialized in the standard fashion when any
- of the procedures are invoked.
- .PP
- For all of these procedures the return value is a standard
- Tcl result: \fBTCL_OK\fR means the expression was succesfully
- evaluated, and \fBTCL_ERROR\fR means that an error occurred while
- evaluating the expression. If \fBTCL_ERROR\fR is returned then
- \fIinterp->result\fR will hold a message describing the error.
- If an error occurs while executing a Tcl command embedded in
- the expression then that error will be returned.
- .PP
- If the expression is successfully evaluated, then its value is
- returned in one of four forms, depending on which procedure
- is invoked.
- \fBTcl_ExprLong\fR stores an integer value at \fI*longPtr\fR.
- If the expression's actual value is a floating-point number,
- then it is truncated to an integer.
- If the expression's actual value is a non-numeric string then
- an error is returned.
- .PP
- \fBTcl_ExprDouble\fR stores a floating-point value at \fI*doublePtr\fR.
- If the expression's actual value is an integer, it is converted to
- floating-point.
- If the expression's actual value is a non-numeric string then
- an error is returned.
- .PP
- \fBTcl_ExprBoolean\fR stores a 0/1 integer value at \fI*booleanPtr\fR.
- If the expression's actual value is an integer or floating-point
- number, then \fBTcl_ExprBoolean\fR stores 0 at \fI*booleanPtr\fR if
- the value was zero and 1 otherwise.
- .VS
- If the expression's actual value is a non-numeric string then
- it must be one of the values accepted by \fBTcl_GetBoolean\fR,
- such as ``yes'' or ``no'', or else an error occurs.
- .VE
- .PP
- \fBTcl_ExprString\fR returns the value of the expression as a
- string stored in \fIinterp->result\fR.
- .VS
- If the expression's actual value is an integer
- then \fBTcl_ExprString\fR converts it to a string using \fBsprintf\fR
- with a ``%d'' converter.
- If the expression's actual value is a floating-point
- number, then \fBTcl_ExprString\fR calls \fBTcl_PrintDouble\fR
- to convert it to a string.
- .VE
-
- .SH KEYWORDS
- boolean, double, evaluate, expression, integer, string
-