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

This commit is contained in:
Arash Partow 2017-02-11 19:51:59 +11:00
parent 177c0e0883
commit b5ec0fec2d
2 changed files with 47 additions and 5 deletions
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8
exprtk.hpp
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@ -2439,10 +2439,10 @@ namespace exprtk
Disallowed: .abc, abc.<white-space>, abc.<eof>, abc.<operator +,-,*,/...> Disallowed: .abc, abc.<white-space>, abc.<eof>, abc.<operator +,-,*,/...>
*/ */
if ( if (
(s_itr_ != initial_itr) && (s_itr_ != initial_itr) &&
!is_end(s_itr_ + 1) && !is_end(s_itr_ + 1) &&
details::is_letter_or_digit(*s_itr_ + 1) && details::is_letter_or_digit(*(s_itr_ + 1)) &&
('_' != (*s_itr_ + 1)) ('_' != (*(s_itr_ + 1)))
) )
break; break;
} }

44
readme.txt
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@ -849,6 +849,48 @@ The above denoted AST will be evaluated in the following order:
(09) Load Variable (w) (09) Load Variable (w)
Generally an expression in ExprTk can be thought of as a free function
similar to those found in imperative languages. This form of pseudo
function will have a name, it may have a set of one or more inputs and
will return at least one value as its result. Futhermore the function
when invoked, may cause a side-effect that changes the state the of
host program.
As an example the following is a pseudo-code definition of a free
function that performs a computation taking four inputs, modifying one
of them and returning a value based on some arbitrary calculation:
ResultType foo(InputType x, InputType y, InputType z, InputType w)
{
w = 2 * x^y + z; // Side-Effect
return abs(x - y) / z; // Return Result
}
Given the above definition the following is a functionally equivalent
version using ExprTk:
const std::string foo_str = " w := 2 * x^y + z; "
" abs(x - y) / z; ";
T x, y, z, w;
symbol_table_t symbol_table;
symbol_table.add_variable("x",x);
symbol_table.add_variable("y",y);
symbol_table.add_variable("z",z);
symbol_table.add_variable("w",w);
expression_t foo;
foo.register_symbol_table(symbol_table);
parser_t parser;
if (parser.compile(foo_str,foo))
{
foo.value();
}
(3) Parser (3) Parser
A component which takes as input a string representation of an A component which takes as input a string representation of an
expression and attempts to compile said input with the result being an expression and attempts to compile said input with the result being an
@ -1293,7 +1335,7 @@ expression that utilizes the function based if-statement.
In the example above, if the condition 'y < z' is true, then the In the example above, if the condition 'y < z' is true, then the
consequent 'y + 1' will be evaluated, it's value will be returned and consequent 'y + 1' will be evaluated, its value will be returned and
subsequently assigned to the variable 'x'. Otherwise the alternative subsequently assigned to the variable 'x'. Otherwise the alternative
'2 * z' will be evaluated and its value will be returned. This is '2 * z' will be evaluated and its value will be returned. This is
essentially the simplest form of an if-then-else statement, As simple essentially the simplest form of an if-then-else statement, As simple