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FX::FXExpression Class Reference

Expression compiles a simple numerical expression into efficient byte-code for repeated evaluation. More...

#include <FXExpression.h>

List of all members.

Public Types

enum  Error {
  ErrOK, ErrEmpty, ErrMemory, ErrParent,
  ErrToken, ErrComma, ErrIdent, ErrColon
}
 Expression error codes. More...

Public Member Functions

 FXExpression ()
 Construct empty expression object.
 FXExpression (const FXExpression &orig)
 Copy expression object.
 FXExpression (const FXchar *expression, const FXchar *variables=NULL, Error *error=NULL)
 Compile expression; if error is not NULL, error code is returned.
 FXExpression (const FXString &expression, const FXString &variables=FXString::null, Error *error=NULL)
 Compile expression; if error is not NULL, error code is returned.
FXExpressionoperator= (const FXExpression &orig)
 Assign another expression to this one.
FXbool empty () const
 See if expression is empty.
FXdouble evaluate (const FXdouble *args=NULL) const
 Evaluate expression with given arguments, if any.
Error parse (const FXchar *expression, const FXchar *variables=NULL)
 Parse expression, return error code if syntax error is found.
Error parse (const FXString &expression, const FXString &variables=FXString::null)
void clear ()
 Clear the expression.
 ~FXExpression ()
 Delete.

Static Public Member Functions

static const FXchar * getError (Error err)
 Returns error code for given error.

Friends

FXAPI FXStreamoperator<< (FXStream &store, const FXExpression &s)
 Saving and loading.
FXAPI FXStreamoperator>> (FXStream &store, FXExpression &s)

Detailed Description

Expression compiles a simple numerical expression into efficient byte-code for repeated evaluation.

When an expression is compiled, an optional comma-separated list of variable names may be passed; during evaluation, values may be provided for these variable by passing an array of values. For instance, when compiling an expression:

  b**2-4*a*c

with the list of variables:

  a,b,c

then a subsequent evaluation can pass an array of three numbers:

  [1 4 2]

which will then evaluate the expression:

  4**2-4*1*2

which should yield:

  8

The expression syntax can be build from the following operators, in order of increasing precedence:

  ? :                     alternate expression
  <, <=, >, >=, ==, !=    comparisons
  <<, >>                  bit-shifts
  &, |, ^                 bit-wise operations
  +, -                    addition and subtraction
  *, /, %                 multiply, divide, modulo
  **                      power
  -, ~                    unary minus, bitwise not
  ( )                     parenthesized subexpressions

The following functions are available:

  abs, acos, acosh, asin, asinh, atan, atanh,
  ceil, cos, cosh, exp, floor, log, log10, sin, sinh,
  sqrt, tan, tanh, max, min, atan2

The expression engine also contains the following constants:

  PI, E, DTOR, RTOD

Variables should not use any of these reserved names.

Initially, FXExpression will be set to a dummy program which will return 0 when evaluated.


Member Enumeration Documentation

Expression error codes.

Enumerator:
ErrEmpty 

No errors.

ErrMemory 

Empty input.

ErrParent 

Out of memory.

ErrToken 

Unmatched parentheses.

ErrComma 

Illegal token.

ErrIdent 

Expected comma.

ErrColon 

Unknown identifier.

Expected colon


Member Function Documentation

FXdouble FX::FXExpression::evaluate ( const FXdouble *  args = NULL) const

Evaluate expression with given arguments, if any.

The array of arguments should match the number of variables passed when compiling the expression.

Error FX::FXExpression::parse ( const FXchar *  expression,
const FXchar *  variables = NULL 
)

Parse expression, return error code if syntax error is found.

If a comma-separated list of variables is passed, then an array of equal number of doubles must be passed when calling evaluate. The values of the array will be read in place of the variable names in the expression.


The documentation for this class was generated from the following file:

Copyright © 1997-2016 Jeroen van der Zijp