EXPR.h

Go to the documentation of this file.

/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        EXPR.h  (C)
 *
 * COMMENTS:    Include file for expression library.
 *
 */

#ifndef __LIBEXPR_H__
#define __LIBEXPR_H__

#include "EXPR_API.h"
#include "EX_Error.h"
#include "EXPR_Lock.h"
#include <UT/UT_SmallObject.h>
#include <UT/UT_String.h>
#include <SYS/SYS_Types.h>
#include <SYS/SYS_MemoryOrder.h>
#include <iosfwd>

class ev_Vector;
class ev_Matrix;
class EX_ExprFunc;
class UT_IStream;
class UT_WorkBuffer;

#define EV_OPTIMIZE0    0               /* No optimization */
#define EV_OPTIMIZE1    1               /* Constant folding */

#define MAX_RECURSION   20              /* Maximum depth of recursion */

#define EV_NHELPARGS    10              /* Maximum # of args in help */

typedef char    *(*ev_Expander)(const char *str, int thread);

/// Valid operator tokens - used by the operator typedef below
/// DON'T CHANGE THESE VALUES - They are saved as ints for compiled expressions.
/// @{
#define OP_PLUS         1               /* + */
#define OP_MINUS        2               /* - */
#define OP_TIMES        3               /* * */
#define OP_DIVIDE       4               /* / */
#define OP_POWER        5               /* ^ */
#define OP_MOD          6               /* % */
#define OP_NOT          7               /* ! */
#define OP_EQ           8               /* == */
#define OP_NE           9               /* != */
#define OP_LT           10              /* < */
#define OP_LE           11              /* <= */
#define OP_GT           12              /* > */
#define OP_GE           13              /* >= */
#define OP_LOGAND       14              /* && (logical and) */
#define OP_LOGOR        15              /* || (logical or) */
#define OP_COMMA        16              /* , almost a NOP */
#define OP_QUESTION     20              /* ? */
#define OP_COLON        21              /* : */
#define OP_AND          22              /* & */
#define OP_OR           23              /* | */
#define OP_DOT          24              /* . */
#define OP_TILDE        25              /* ~ */
#define OP_AT           26              /* @ */
#define OP_SBRACKET     30              /* [ end square bracket implied */
#define OP_BRACE        31              /* { end brace implied */
#define OP_EQUATE       32              /* = */
#define MAX_OPERATOR_TOKEN 32
/// @}

/// These flags are common to symbols, operators and functions
///
/// NOTE: The high 8 bits of the flag are reserved for internal use
///       User flags should start at not go higher than 0x800000
///
/// Note: when changing this definition, update EX_USERFLAGMASK 
/// @{
#define EV_SYMTRANSIENT 0x04000000      ///< Symbol is result of operation
#define EV_SYMCONSTANT  0x08000000      ///< Symbol has a constant value
#define EV_FLAGS_SET    0x10000000      ///< User flags have been set
#define EV_SYMEXPAND    0x20000000      ///< String should be expanded
#define EV_EXFUNC_REF   0x40000000      ///< Refers to an expression function
#define EV_FOR_EXFUNC   0x80000000      ///< Symbol is to be used by expr func
/// @}

#define EX_USERFLAGMASK (0x03ffffff | EV_EXFUNC_REF)


/// Implicit types known by expression language
///     - The type identifiers must be positive unique integers
///     - Eventhough Variables are handled as a special case, the
///             type identifier for each variable type must be unique
///     - It is suggested that applications start their typedefs identifiers
///             10 or greater.  The identifiers do not have to be sequential.
///
/// DON'T CHANGE THESE VALUES - They are saved as ints for compiled expressions.
/// @{
#define EV_TYPEFLOAT                    0       ///< Float type of symbol
#define EV_TYPESTRING                   1       ///< String type of symbol
#define EV_TYPEUNIXVAR                  2       ///< Unix variable type
#define EV_TYPEEXPANDVAR                4       ///< Variable of form ${foo$x}
#define EV_TYPEVECTOR                   5       ///< Vector
#define EV_TYPEMATRIX                   6       ///< Matrix
/// @}

/// These types are used in Houdini outside of EXPR.
/// DON'T CHANGE THESE VALUES - They are saved as ints for compiled expressions.
/// @{
#define EV_TYPE_LOCAL_VAR               10      ///< A node local variable
#define EV_TYPE_UNRESOLVED_VAR          11      ///< An unknown variable
#define EV_TYPE_DEFINE                  12
#define EV_TYPE_GEOATTRIBUTE            13      ///< An attribute reference
#define EV_TYPE_GLOBAL_VAR              20      ///< A global variable
#define EV_TYPE_CPPSYMBOL               45      ///< A symbol inside a function
#define EV_TYPE_UNRESOLVED_CPPSYMBOL    46      ///< An unknown function symbol
/// @}

/// Typedefs for structures in the expression library
///     SYMBOL   - any data in the expression (i.e. fpreal, string, variable)
///     TYPEDEF  - a definition for a type (i.e. fpreal, string, etc.)
///                     Defines how to handle this data type
///     OPERATOR - binary or unary operator which takes symbol(s) and
///                     performs some action resulting in a new symbol
///     FUNCTION - function which takes arguments and performs some action
///                     on them to produce a new symbol
///     EXPRESSION - the type seen to the outside world
/// @{
class EV_FUNCTION;
struct EV_SYMBOL;
typedef struct EV_TYPEDEF       EV_TYPEDEF;
typedef struct EV_OPERATOR      EV_OPERATOR;
typedef struct EV_FUNCHELP      EV_FUNCHELP;
/// @}

/// This callback is used to scan for op dependencies and add/remove
/// dependencies.  Unlike evaluation, this callback can have null arguments.
/// A null argument signifies a non-constant parameter to the function.
typedef void    (*EXPRopDependencyCallback)(EV_FUNCTION *me,
                                            EV_SYMBOL **argv,
                                            void *ref_id);
typedef void    (*EXPRopChangeRefCallback)(EV_FUNCTION *me,
                                          EV_SYMBOL **argv,
                                          char *new_args[],
                                          const char *new_fullpath,
                                          const char *old_fullpath,
                                          const char *old_cwd,
                                          const char *chan_name,
                                          const char *old_chan_name);

/// union used to hold a token's value
typedef union {
        fpreal          fval;
        char            *sval;
        void            *data;
} EV_TOKENVALUE;

/// class representing a symbol operated upon by expressions
struct EXPR_API EV_SYMBOL
{
        bool            isForExprFunc() const
                            { return ((flag & EV_FOR_EXFUNC) != 0); }
        void            setForExprFunc()
                            { flag |= EV_FOR_EXFUNC; }
        bool            isConstant() const
                            { return ((flag & EV_SYMCONSTANT) != 0); }
        bool            isTransient() const
                            { return ((flag & EV_SYMTRANSIENT) != 0); }

        unsigned        flag;   ///< Flag for symbols
        EV_TYPEDEF      *type;  ///< Interpretation of data
        EV_TOKENVALUE   value;  ///< Token data
        EV_SYMBOL       *next;  ///< Used Internally
        int             pos;    ///< String pos in expression
};

struct EV_TYPEDEF {
        int             type;
        const char      *name;                  /* Name of type */
        void            (*allocValue)(EV_SYMBOL *);
        void            (*freeValue)(EV_SYMBOL *);
        EV_SYMBOL       *(*resolveSymbol)(const char *, int thread);
        const char      *(*getName)(EV_SYMBOL *);
        int             (*castValue)(EV_SYMBOL *to, EV_SYMBOL *me, int thread);
        int             (*castFrom)(EV_SYMBOL *me, EV_SYMBOL *from);
        void            (*copyValue)(EV_SYMBOL *dest, EV_SYMBOL *src, int thread);
        int             (*getCastType)(EV_SYMBOL *src);
        void            (*opDepend)(EV_SYMBOL *src, void *ref_id);

        EV_TYPEDEF      *next;                  /* Used Internally */
        EV_TYPEDEF      *varnext;               /* Used Internally */
};

/// struct describing an operator's characteristics
struct EV_OPERATOR {
        int             flag;           ///< Flag for operator
        int             token;          ///< OP_ token to identify
        unsigned char   binary;         ///< Binary or unary operator
        int             leftType;       ///< Data for left side of op
        int             rightType;      ///< Data for right side of op
        int             resultType;     ///< Resultant type of op

        void            (*evaluate)(EV_SYMBOL *, EV_SYMBOL *, EV_SYMBOL *);

        EV_OPERATOR     *next;          ///< Used internally
};

/// Handy macros for defining expression functions.
/// They only differ by which function parameters are supplied to avoid
/// unused parameter warnings.
/// @{
#define EV_START_FN(name)        \
            static void name(EV_FUNCTION *, EV_SYMBOL *result,\
                             EV_SYMBOL **argv, int thread, unsigned &func_flags)
#define EV_START_FNNA(name) \
            static void name(EV_FUNCTION *, EV_SYMBOL *result, \
                             EV_SYMBOL **, int thread, unsigned &func_flags)
#define EV_START_FUNC(name) \
            static void name(EV_FUNCTION *func, EV_SYMBOL *result,\
                             EV_SYMBOL **argv, int thread, unsigned &func_flags)
#define EV_END_FN(answer)        \
            result->value.fval = (answer)
#define EV_END_FNS(answer)       \
            result->value.sval = (answer)
/// @}

typedef void (*EXPRfuncCallback)(EV_FUNCTION *me,
                                 EV_SYMBOL *result,
                                 EV_SYMBOL **argv,
                                 int thread,
                                 unsigned &func_flags);

///
class EXPR_API EV_FUNCTION {
public:
    EV_FUNCTION(unsigned         flag = 0,
                const char      *name = 0,
                int              num_args = 0,
                int              result_type = EV_TYPEFLOAT,
                const int       *argTypes = 0,
                EXPRfuncCallback callback = 0,
                EXPRopDependencyCallback        dependCB = 0,
                EXPRopChangeRefCallback         changeOpRefCB = 0,
                int              is_safe = 1,
                bool             is_threadsafe = false);
    virtual ~EV_FUNCTION();

    virtual int64 getMemoryUsage(bool inclusive) const;

    unsigned     getUserFlags() const           { return myUserFlags; }
    const char  *getName() const        { return myName; }
    int          getNArgs() const       { return myNArgs; }
    int          getResultType() const  { return myResultType; }
    const int   *getArgTypes() const    { return myArgTypes; }
    int          getArgType(int i) const        { return myArgTypes[i]; }
    const char  *getDSOLocation() const { return myDSOLocation; }

    /// getInstanceData() returns the instance data for the current evaluating
    /// expression function
    static void *getInstanceData(int thread);
    static void  setInstanceAllocator(const char *function,
                                      void *(*alloc)(), void (*freer)(void *));
    void         setInstanceAllocator(void *(*alloc)(), void (*freer)(void *))
                 {
                     myAllocator = alloc;
                     myFreer = freer;
                 }
    void        *allocInstanceData() { return myAllocator ? myAllocator() : 0; }
    void         freeInstanceData(void *d) { myFreer(d); }

    void         setOpDependencyCallback(EXPRopDependencyCallback cb)
                 {
                     myDependCallback = cb;
                 }
    void         setChangeOpRefCallback(EXPRopChangeRefCallback cb)
                 {
                     myChangeOpRefCallback = cb;
                 }

    // isSafe() tells us if we can call this expression function when the
    // expression evaluator is in "safe" mode.
    int          isSafe() const { return myIsSafe; }

    void         setIsThreadSafe(bool flag) { myIsThreadSafe = flag; }
    bool         isThreadSafe() const       { return myIsThreadSafe; }

public:
    EXPRfuncCallback            myCallback;
    EXPRopDependencyCallback    myDependCallback;
    EXPRopChangeRefCallback     myChangeOpRefCallback;

private:
    const char          *myName;
    char                *myDSOLocation;
    int                  myNArgs;
    int                  myResultType;
    const int           *myArgTypes;
    void                *(*myAllocator)();
    void                 (*myFreer)(void *);
    unsigned             myUserFlags;
    unsigned             myIsSafe:1,
                         myIsThreadSafe:1;
};


/// This is an enumeration of the type of return values that an inline
/// function may be expected to return.  Setting this value to 
/// EV_EXPR_RETURN_NONE will disallow an expression from supporting inline
/// functions.
enum EV_InlineFuncReturnType
{
    EV_EXPR_RETURN_NONE,
    EV_EXPR_RETURN_FLOAT,
    EV_EXPR_RETURN_STRING,
    EV_EXPR_RETURN_VECTOR,
    EV_EXPR_RETURN_MATRIX
};


/// Structure used as the parameter to ev_ChangeOpReference
/// (Currently only used internally)
struct EV_ChangeOpReferenceParms
{
    const char    *new_fullpath;
    const char    *old_fullpath;
    const char    *old_cwd;
    const char    *chan_name;
    const char    *old_chan_name;
};

class in_INSTRUCTION;

class EXPR_API EV_EXPRESSION
                    : public UT_SmallObject<EV_EXPRESSION,
                                            UT_SMALLOBJECT_CLEANPAGES_DEFAULT,
                                            UT_SMALLOBJECT_PAGESIZE_DEFAULT,
                                            UT_SMALLOBJECT_THREADSAFE_ON>
{
public:
    EV_EXPRESSION(EV_InlineFuncReturnType ret_type)
    {
        myFlags = 0;
        mySource = 0;
        myCompiled = 0;
        myRecurs = 0;
        myFunc = 0;
        myFuncRetType = ret_type;
        myInExprFunc = false;
        myNeedResolveVars = false;
        myIsPureCompiled = false;
    }
    ~EV_EXPRESSION()
    {
        freeExprSpace();
    }

    int64           getMemoryUsage(bool inclusive) const;

    /// Common evaluation functions.
    /// NOTES:
    ///   - These functions will cast to the desired return type.
    ///   - The thread parameter should be equivalent to SYSgetSTID()
    /// @{
    bool            evaluate(int thread, fpreal &result);
    bool            evaluate(int thread, UT_String &result);
    bool            evaluate(int thread, ev_Vector &result);
    bool            evaluate(int thread, ev_Matrix &result);
    /// @}

    /// Raw evaluation function that does no casting.
    /// @{
    EV_SYMBOL *     evaluate(int thread)
                        { return evaluate(myFuncRetType, thread); }
    EV_SYMBOL *     evaluate(EV_InlineFuncReturnType func_ret_type, int thread);
    /// @}

    bool            changeExpr(const char *source);
    void            unresolveVars(int thread);
    void            dirtyExpr();

    /// Dependencies
    /// @{
    void            updateOpDependency(void *ref_id, int thread);
    int             changeOpReference(const char *new_fullpath,
                                      const char *old_fullpath,
                                      const char *old_cwd,
                                      const char *chan_name,
                                      const char *old_chan_name,
                                      int thread);
    /// @}

    /// Save and load compiled expressions
    /// @{
    bool            saveCompiledCode(std::ostream &os, int thread);
    bool            loadCompiledCode(UT_IStream &is, int thread);
    /// @}

    /// Thread-Safe Flags Access
    /// @{
    unsigned int    getFlags() const
                    { 
                        // Synchronize with SYSstoreFence() in evaluate()
                        // where we set myFlags
                        unsigned flags = 
                            *static_cast<unsigned const volatile *>(&myFlags);
                        SYSloadFence();
                        return flags;
                    }
    bool            hasFlag(unsigned int bit) const
                        { return ((getFlags() & bit) != 0); }
    bool            isEvaluated() const
                        { return ((getFlags() & EV_FLAGS_SET) != 0); }
    SYS_DEPRECATED_REPLACE(17.5, "clearAllFlagsUnsafe")
    void            clearAllFlags()
                        { myFlags = 0; }
    SYS_DEPRECATED_REPLACE(17.5, "setFlagsUnsafe")
    void            setFlags(unsigned int flags)
                        { myFlags = flags; }
    SYS_DEPRECATED_REPLACE(17.5, "appendFlagsUnsafe")
    void            appendFlags(unsigned int flag)
                        { myFlags |= flag; }
    SYS_DEPRECATED_REPLACE(17.5, "setEvaluatedUnsafe")
    void            setEvaluated()
                        { myFlags |= EV_FLAGS_SET; }
    SYS_DEPRECATED_REPLACE(17.5, "clearFlagsBeforeEvaluationUnsafe")
    void            clearFlagsBeforeEvaluation()
                        { myFlags &= ~(EX_USERFLAGMASK | EV_FLAGS_SET); }

    /// @}

    /// Non-Thread-Safe Flags Access. Writes need to be locked using getLock().
    /// @{
    unsigned int    getFlagsUnsafe() const
                        { return myFlags; }
    bool            hasFlagUnsafe(unsigned int bit) const
                        { return ((myFlags & bit) != 0); }
    void            clearAllFlagsUnsafe()
                        { myFlags = 0; }
    void            setFlagsUnsafe(unsigned int flags)
                        { myFlags = flags; }
    void            appendFlagsUnsafe(unsigned int flag)
                        { myFlags |= flag; }
    void            setEvaluatedUnsafe()
                        { myFlags |= EV_FLAGS_SET; }
    bool            isEvaluatedUnsafe() const
                        { return ((myFlags & EV_FLAGS_SET) != 0); }

    /// This function is called before evaluating EXPR expressions and python
    /// expressions to clear the appropriate flags on the expression.
    void            clearFlagsBeforeEvaluationUnsafe()
                        { myFlags &= ~(EX_USERFLAGMASK | EV_FLAGS_SET); }
    /// @}

    /// Other accesors
    /// @{
    const char *    getSource() const
                        { return mySource; }
    bool            isCompiled() const
                        { return (myCompiled != 0); }

    bool            isPureCompiled() const
                        { return myIsPureCompiled; }

    /// getSingleFunctionInstanceData() returns the instance data for this
    /// expression's function which must be of form func("literal").
    /// Returns NULL if this expression doesn't have the right form.
    void *          getSingleFunctionInstanceData(
                        EV_FUNCTION *func, int thread, UT_String &argument);

    /// isInExprFunc() says whether we are an expression inside a custom expr
    /// function. It is turned on in EX_ExprFunc.
    bool            isInExprFunc() const
                        { return myInExprFunc; }
    void            setInExprFunc(bool is_inside)
                        { myInExprFunc = is_inside; }
    /// @}

    EV_InlineFuncReturnType
                    getInlineFuncRetType() const
                        { return myFuncRetType; }
    void            setInlineFuncRetType(EV_InlineFuncReturnType ret_type)
                        { myFuncRetType = ret_type; }

    /// Return a reference for thread-safe access
    EXPR_Lock &     getLock() const
                        { return myLock; }

private:    // methods
    void            freeCompiledExpr(EV_SYMBOL *&free_list);
    bool            parseInlineFunc(UT_String &func_call, int thread);
    int             compile(const char *tstring, int thread,
                            bool ignore_bad_vars);
    int             parseExpr(EV_InlineFuncReturnType func_ret_type,
                              int thread, bool ignore_bad_vars);
    bool            freeExprSpace();
    void            doUpdateOpDependency(void *ref_id, int thread);
    int             doChangeOpReference(UT_String &new_source,
                                        EV_ChangeOpReferenceParms &parms,
                                        int thread);

private:    // data
    unsigned                     myFlags;       /* Expression flag */
    char                        *mySource;      /* Readable expression */
    in_INSTRUCTION              *myCompiled;    /* Compiled expression */
    int                          myRecurs;      /* Recursion count */
    EX_ExprFunc                 *myFunc;        /* Inline function */
    EV_InlineFuncReturnType      myFuncRetType; /* Return type for inline func*/
    mutable EXPR_Lock            myLock;
    bool                         myInExprFunc:1;/* Inside a custom EXPR func*/
    bool                         myNeedResolveVars:1;
    // True if the expression was loaded as a compiled 
    // expression, false otherwise.
    bool                         myIsPureCompiled:1;
};

/// initialize floating point operations
/// Float initialization will automatically initialize vector/matrix
EXPR_API extern void            ev_InitFloat();
/// initialize string operations
EXPR_API extern void            ev_InitString();
EXPR_API extern void            ev_InitVariable();
/// initialize vector operations
EXPR_API extern void            ev_InitVector();
/// initialize matrix operations
EXPR_API extern void            ev_InitMatrix();
EXPR_API extern void            ev_InitUserFunc();

///  Functions for expansion of library
///     Add operators, type definitions and functions.
/// @{
EXPR_API extern void            ev_AddType(EV_TYPEDEF *type);
EXPR_API extern void            ev_AddVariableType(EV_TYPEDEF *type, int atEnd);
EXPR_API extern void            ev_DeleteVariableType(EV_TYPEDEF *type);
EXPR_API extern void            ev_AddOperator(EV_OPERATOR *op, int level);
EXPR_API extern void            ev_AddFunction(EV_FUNCTION *func);
EXPR_API extern void            ev_DeleteFunction(EV_FUNCTION *func);
EXPR_API extern void            ev_SetOptimization(int level);
/// @}

EXPR_API extern void            ev_PrintHelp(std::ostream &os, const char *match,
                                             const char *keyword, 
                                             bool full_match_only = false);

EXPR_API extern int              ev_GetNFunctions();
EXPR_API extern EV_FUNCTION     *ev_GetFunction(int i);
EXPR_API extern EV_TYPEDEF      *ev_GetTypeDef(int key);
EXPR_API extern int              ev_FindFunction(const char *name);

/// Functions for supplying state data for custom expressions.
// @{

/// This function specifies the constructor/destructor functions for the 
/// state data.
/// @param function     Name of the custom expression function
/// @param alloc        This allocates and initializes the state data
/// @param free         This deallocates the state data
EXPR_API extern void             ev_SetFunctionInstanceAllocator(
                                                const char *function,
                                                void *(*alloc)(),
                                                void (*free)(void *));

/// From within an expression function, use this to retrieve the data created
/// by the alloc function specified in ev_SetFunctionInstanceAllocator().
/// @param thread       Thread id supplied to the expression function callback
EXPR_API extern void            *ev_GetFunctionData(int thread);

// @}

EXPR_API extern void             ev_SetFunctionDependencyCallbacks(
                                        const char *func,
                                        EXPRopDependencyCallback depend_cb,
                                        EXPRopChangeRefCallback changeref_cb);

// Basic level of operation as seen by application
EXPR_API extern EV_EXPRESSION   *ev_AllocExpr(EV_InlineFuncReturnType rettype);
EXPR_API extern int              ev_ChangeExpr(EV_EXPRESSION *expr,
                                                const char *source);
EXPR_API extern void             ev_UnresolveVars(EV_EXPRESSION *expr,
                                                  int thread);
EXPR_API extern fpreal           ev_EvaluateFloat(EV_EXPRESSION *expr,
                                                int thread);
EXPR_API extern void             ev_EvaluateString(UT_String &result,
                                                   EV_EXPRESSION *expr,
                                                   int thread);
EXPR_API extern int              ev_EvaluateVector(EV_EXPRESSION *expr,
                                                ev_Vector &result,
                                                int thread);
EXPR_API extern int              ev_EvaluateMatrix(EV_EXPRESSION *expr,
                                                ev_Matrix &result,
                                                int thread);
EXPR_API extern void             ev_FreeExpr(EV_EXPRESSION *expr);

EXPR_API extern void             ev_UpdateOpDependency(EV_EXPRESSION *expr,
                                                void *ref_id, int thread);
EXPR_API extern int              ev_ChangeOpReference(EV_EXPRESSION *expr,
                                                const char *new_fullpath,
                                                const char *old_fullpath,
                                                const char *old_cwd,
                                                const char *chan_name,
                                                const char *old_chan_name,
                                                int thread);
EXPR_API extern EV_SYMBOL       *ev_Evaluate(
                                    EV_EXPRESSION *expr,
                                    EV_InlineFuncReturnType func_ret_type,
                                    int thread);

/// These functions save and load compiled expressions.
/// @{
EXPR_API extern bool             ev_SaveCompiledCode(EV_EXPRESSION *expr,
                                                std::ostream &os, int thread);
EXPR_API extern bool             ev_LoadCompiledCode(EV_EXPRESSION *expr,
                                                UT_IStream &is, int thread);
/// @}

/// Functions used internally by type declarations
/// @{
EXPR_API extern EV_SYMBOL       *ev_AllocSymbol(int type, int thread);
EXPR_API extern void             ev_FreeSymbol(EV_SYMBOL *symbol, int thread);
/// @}

/// Nice conversion of float to string data.  This will do simple checks to try
/// to convert integer values more correctly.
EXPR_API extern void    EXPRftoa(UT_WorkBuffer &buf, fpreal v);

/// Following are the defines/typedefs for the language handler
/// @{
typedef struct EV_SYMTABLE      EV_SYMTABLE;

struct EV_SYMTABLE {                    /* Used internally */
        int             flag;
        char            *name;
        fpreal          *value;         /* Value of symbol */
        EV_SYMBOL       *sym;           /* symbol       */
        EV_SYMTABLE     *next;
};

struct EV_FUNCHELP {
        char            *name;                  /* Name of the function */
        char            *argname[EV_NHELPARGS]; /* Arg names */
        char            *description;           /* A brief description */
};
/// @}

EXPR_API extern void            ev_SetExpander(ev_Expander expander);

/// These functions put the expression evaluator into/out of "safe" mode.
/// In safe mode, certain functions will not be executed.
/// @{
EXPR_API extern void             ev_setSafeMode(bool safe_mode);
EXPR_API extern bool             ev_isInSafeMode();
EXPR_API extern bool             ev_isKeyword(const char *string);
/// @}

#endif