1Tcl_ExprLong(3) Tcl Library Procedures Tcl_ExprLong(3)
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6
8 Tcl_ExprLong, Tcl_ExprDouble, Tcl_ExprBoolean, Tcl_ExprString - evalu‐
9 ate an expression
10
12 #include <tcl.h>
13 int
15 Tcl_ExprLong(interp, expr, longPtr)
16 int
18 Tcl_ExprDouble(interp, expr, doublePtr)
19 int
21 Tcl_ExprBoolean(interp, expr, booleanPtr)
22 int
24 Tcl_ExprString(interp, expr)
25
27 Tcl_Interp *interp (in) Interpreter in whose context to
28 evaluate expr.
29 const char *expr (in) Expression to be evaluated.
31 long *longPtr (out) Pointer to location in which to
33 store the integer value of the
34 expression.
35 int *doublePtr (out) Pointer to location in which to
37 store the floating-point value of
38 the expression.
39 int *booleanPtr (out) Pointer to location in which to
41 store the 0/1 boolean value of the
42 expression.
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44
47 These four procedures all evaluate the expression given by the expr
48 argument and return the result in one of four different forms. The
49 expression can have any of the forms accepted by the expr command.
50 Note that these procedures have been largely replaced by the value-
51 based procedures Tcl_ExprLongObj, Tcl_ExprDoubleObj, Tcl_Expr‐
52 BooleanObj, and Tcl_ExprObj. Those value-based procedures evaluate an
53 expression held in a Tcl value instead of a string. The value argument
54 can retain an internal representation that is more efficient to exe‐
55 cute.
56 The interp argument refers to an interpreter used to evaluate the
58 expression (e.g. for variables and nested Tcl commands) and to return
59 error information.
60 For all of these procedures the return value is a standard Tcl result:
62 TCL_OK means the expression was successfully evaluated, and TCL_ERROR
63 means that an error occurred while evaluating the expression. If
64 TCL_ERROR is returned then the interpreter's result will hold a message
65 describing the error. If an error occurs while executing a Tcl command
66 embedded in the expression then that error will be returned.
67 If the expression is successfully evaluated, then its value is returned
69 in one of four forms, depending on which procedure is invoked.
70 Tcl_ExprLong stores an integer value at *longPtr. If the expression's
71 actual value is a floating-point number, then it is truncated to an
72 integer. If the expression's actual value is a non-numeric string then
73 an error is returned.
74 Tcl_ExprDouble stores a floating-point value at *doublePtr. If the
76 expression's actual value is an integer, it is converted to floating-
77 point. If the expression's actual value is a non-numeric string then
78 an error is returned.
79 Tcl_ExprBoolean stores a 0/1 integer value at *booleanPtr. If the
81 expression's actual value is an integer or floating-point number, then
82 they store 0 at *booleanPtr if the value was zero and 1 otherwise. If
83 the expression's actual value is a non-numeric string then it must be
84 one of the values accepted by Tcl_GetBoolean such as “yes” or “no”, or
85 else an error occurs.
86 Tcl_ExprString returns the value of the expression as a string stored
88 in the interpreter's result.
89
92 Tcl_ExprLongObj, Tcl_ExprDoubleObj, Tcl_ExprBooleanObj, Tcl_ExprObj
93
96 boolean, double, evaluate, expression, integer, value, string
97Tcl 7.0 Tcl_ExprLong(3)