xfygogo/exprtk
1
0
Fork 0
mirror of https://github.com/ArashPartow/exprtk.git synced 2025-06-12 16:27:23 +00:00
Code Issues Packages Projects Releases Wiki Activity

C++ Mathematical Expression Library (ExprTk) http://www.partow.net/programming/exprtk/index.html

Browse Source
This commit is contained in:
Arash Partow
2014-12-14 17:38:05 +11:00
parent ebf3f14ca6
commit e105e6278c
3 changed files with 759 additions and 348 deletions
Download Patch File Download Diff File Expand all files Collapse all files

184
readme.txt
View File

@ -50,7 +50,7 @@ arithmetic operations, functions and processes:
[02 - EXAMPLE EXPRESSIONS]
The following is a short listing of the types of mathematical
The following is a short listing of the types of mathematical
expressions that can be parsed and evaluated using the ExprTk library.
(01) sqrt(1 - (3 / x^2))
@ -1253,16 +1253,37 @@ Compile-time type checking of input parameters can be requested by
passing a string to the constructor of the igeneric_function that
represents the required sequence of parameter types. When no parameter
sequence is provided, it is implied the function can accept a variable
number of parameters comprised of any of the fundemental types. The
following example demonstrates how this can be achieved:
number of parameters comprised of any of the fundamental types.
Each fundamental type has an associated character. The following is a
listing of said characters and their meanings:
(1) T - Scalar
(2) V - Vector
(3) S - String
(4) ? - Any type (Scalar, Vector or String)
(5) * - Wildcard operator
(6) | - Parameter sequence delimiter
No other characters other than the six denoted above may be included
in the parameter sequence definition. If any such invalid characters
do exist, registration of the associated generic function to a symbol
table ('add_function' method) will fail. If the parameter sequence is
modified resulting in it becoming invalid after having been added to
the symbol table but before the compilation step, a compilation error
will be incurred.
The following example demonstrates a simple generic function
implementation with a user specified parameter sequence:
template <typename T>
struct too : public exprtk::igeneric_function<T>
struct moo : public exprtk::igeneric_function<T>
{
typedef typename exprtk::igeneric_function<T>::parameter_list_t
parameter_list_t;
too()
moo()
: exprtk::igeneric_function<T>("SVTT")
{}
@ -1273,45 +1294,13 @@ following example demonstrates how this can be achieved:
};
In the example above the custom generic function 'too' expects
exactly four parameters in the following sequence:
(a) String
(b) Vector
(c) Scalar
(d) Scalar
One further refinement to the type checking facility is the
possibility of a variable number of trailing common types which can be
accomplished by using a wildcard '*' at the end of the sequence
definition.
template <typename T>
struct too : public exprtk::igeneric_function<T>
{
typedef typename exprtk::igeneric_function<T>::parameter_list_t
parameter_list_t;
too()
: exprtk::igeneric_function<T>("SVTTV*")
{}
inline T operator()(parameter_list_t parameters)
{
...
}
};
In the example above the generic function 'too' expects at least five
In the example above the generic function 'moo' expects exactly four
parameters in the following sequence:
(a) String
(b) Vector
(c) Scalar
(d) Scalar
(e) One or more Vectors
(1) String
(2) Vector
(3) Scalar
(4) Scalar
(4) igeneric_function II
@ -1326,7 +1315,7 @@ situations such as concatenation and equality operations.
The following example defines an generic function named 'toupper' with
the string return type function operator being explicitly overriden:
the string return type function operator being explicitly overridden:
template <typename T>
struct toupper : public exprtk::igeneric_function<T>
@ -1354,12 +1343,16 @@ the string return type function operator being explicitly overriden:
In the example above the generic function 'toupper' expects only one
input parameter of type string, as noted by the parameter sequence
input parameter of type string, as noted by the parameter sequence
string passed during the constructor. When executed, the function will
return as a result a copy of the input string converted to uppercase
form.
form. An example expression using the toupper function registered as
the symbol 'toupper' is as follows:
When adding a string type returning generic function to a symbol
"'ABCDEF' == toupper('aBc') + toupper('DeF')"
Note: When adding a string type returning generic function to a symbol
table, the 'add_function' is invoked with an extra parameter
(e_ft_strfunc) that denotes the function should be treated as a string
returning function type. The following example demonstrates how this
@ -1374,6 +1367,99 @@ is done:
symbol_table_t::e_ft_strfunc);
Note: There are two further refinements to the type checking facility
are the possibilities of a variable number of common types which can
be accomplished by using a wildcard '*' and a special 'any type' which
is done using the '?' character. It should be noted that the wildcard
operator is associated with the previous type in the sequence and
implies one or more of that type.
template <typename T>
struct zoo : public exprtk::igeneric_function<T>
{
typedef typename exprtk::igeneric_function<T>::parameter_list_t
parameter_list_t;
zoo()
: exprtk::igeneric_function<T>("SVT*V?")
{}
inline T operator()(parameter_list_t parameters)
{
...
}
};
In the example above the generic function 'zoo' expects at least five
parameters in the following sequence:
(1) String
(2) Vector
(3) One or more Scalars
(4) Vector
(5) Any type (one type of either a scalar, vector or string)
A final piece of type checking functionality is available for the
scenarios where a single function name is intended to be used for
multiple distinct parameter sequences. Two specific overrides of the
function operator are provided one for standard generic functions and
one for string returning functions. The overrides are as follows:
// f(psi,i_0,i_1,....,i_N) --> Scalar
inline T operator()(const std::size_t& ps_index,
parameter_list_t parameters)
{
...
}
// f(psi,i_0,i_1,....,i_N) --> String
inline T operator()(const std::size_t& ps_index,
std::string& result,
parameter_list_t parameters)
{
...
}
When the function operator is invoked the 'ps_index' parameter will
have as its value the index of the parameter sequence that matches the
specific invocation. This way complex and time consuming type checking
conditions need not be executed in the function itself but rather a
simple and efficient dispatch to a specific implementation for that
particular parameter sequence can be performed.
template <typename T>
struct roo : public exprtk::igeneric_function<T>
{
typedef typename exprtk::igeneric_function<T>::parameter_list_t
parameter_list_t;
moo()
: exprtk::igeneric_function<T>("SVTT|SS|TTV|S?V*S")
{}
inline T operator()(parameter_list_t parameters)
{
...
}
};
In the above example there are four distinct parameter sequences that
can be processed by the generic function 'roo'. Any other parameter
sequences will cause a compilation error. The valid four sequences are
as follows:
Sequence-0 Sequence-1 Sequence-2 Sequence-3
'SVTT' 'SS' 'TTV' 'S?V*S'
(1) String (1) String (1) Scalar (1) String
(2) Vector (2) String (2) Scalar (2) Any Type
(3) Scalar (3) Vector (3) One or more Vectors
(4) Scalar (4) String
(5) function_compositor
The function compositor interface allows a user to define a function
using ExprTk syntax. The functions are limited to returning a single
@ -1745,7 +1831,7 @@ into account when using Exprtk:
(28) Every valid ExprTk statement is a "value returning" expression.
Unlike some languages that limit the types of expressions that
can be performed in certain situations, in ExprTk any valid
expression can be used in any "value consuming" context. Eg:
expression can be used in any "value consuming" context. eg:
var y := 3;
for (var x := switch
@ -2045,7 +2131,9 @@ files:
+-------------------------------------------------------------+
|09 - Variable Definition Statement |
| |
| [var] ---> [symbol] -+-> [:=] ---> [expression] -+-> [;] |
| [var] ---> [symbol] -+-> [:=] -+-> [expression] -+-> [;] |
| | | | |
| | +-----> [{}] -->--+ |
| | | |
| +------------->-------------+ |
| |