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

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Arash Partow
2014-04-07 07:01:02 +10:00
parent 904f924005
commit e5f917033f
3 changed files with 323 additions and 138 deletions
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readme.txt
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@ -32,7 +32,8 @@ arithmetic operations, functions and processes:
(5) Conditional,
Switch &
Loop statements: if-then-else, switch-case, while, repeat-until
Loop statements: if-then-else, ternary conditional, switch-case,
while, repeat-until
(6) Assignment: :=
@ -64,7 +65,7 @@ expressions that can be parsed and evaluated using the ExprTk library.
(13) (x + y)z + 1.1 / 2.7 == (x + y) * z + 1.1 / 2.7
(14) (sin(x / pi) cos(2y) + 1) == (sin(x / pi) * cos(2 * y) + 1)
(15) 75x^17 + 25.1x^5 - 35x^4 - 15.2x^3 + 40x^2 - 15.3x + 1
(16) if (avg(x,y) <= x + y, x - y, x * y) + 2.345 * pi / x
(16) (avg(x,y) <= x + y ? x - y : x * y) + 2.345 * pi / x
(17) fib_i := fib_i + (x := y + 0 * (fib_i := x + (y := fib_i)))
(18) while (x <= 100) { x := x + 1 }
(19) x <= 'abc123' and (y in 'AString') or ('1x2y3z' != z)
@ -406,6 +407,13 @@ include path (e.g: /usr/include/).
| | w := z + y; |
| | until ((x := (x - 1)) <= 0) |
+----------+---------------------------------------------------------+
| ?: | Ternary conditional statement, similar to that of the |
| | above denoted if-statement. |
| | eg: |
| | 0. x ? y : z |
| | 1. x + 1 > 2y ? z + 1 : (w / v) |
| | 2. min(x,y) > z ? (x < y + 1) ? x : y : (w * v) |
+----------+---------------------------------------------------------+
| ~ | Evaluate each sub-expression, then return as the result |
| | the value of the last sub-expression. This is sometimes |
| | known as multiple sequence point evaluation. |
@ -459,6 +467,46 @@ types a symbol table can handle:
(e) Functions
(f) Vararg functions
During the compilation process if an expression is found to require
any of the elements noted above, the expression's associated
symbol_table will be queried for the element and if present a
reference to the element will be embedded within the expression's AST.
This allows for the original element to be modified independently of
the expression instance and to also allow the expression to be
evaluated using the current value of the element.
The example below demonstrates the relationship between variables,
symbol_table and expression. Note the variables are modified as they
normally would in a program, and when the expression is evaluated the
current values assigned to the variables will be used.
typedef exprtk::symbol_table<double> symbol_table_t;
typedef exprtk::expression<double> expression_t;
typedef exprtk::parser<double> parser_t;
symbol_table_t symbol_table;
expression_t expression;
parser_t parser;
double x = 0;
double y = 0;
std::string expression_string = "x * y + 3";
symbol_table.add_variable("x",x);
symbol_table.add_variable("y",y);
expression.register_symbol_table(symbol_table);
parser.compile(expression_string,expression);
x = 1.0;
y = 2.0;
parser.value(); // 1 * 2 + 3
x = 3.7;
parser.value(); // 3.7 * 2 + 3
y = -9.0;
parser.value(); // 3.7 * -9 + 3
(2) Expression
A structure that holds an AST for a specified expression and is used
@ -474,21 +522,21 @@ Expression: z := (x + y^-2.345) * sin(pi / min(w - 7.3,v))
[Assignment]
________/ \_____
/ \
Variable(z) [Multiply]
Variable(z) [Multiplication]
____________/ \___________
/ \
/ [Unary-Func(sin)]
[Addition] |
____/ \____ [Division]
/ \ ___/ \___
Variable(x) [Power] / \
Variable(x) [Exponentiation] / \
______/ \______ Constant(pi) [Binary-Func(min)]
/ \ ____/ \____
Variable(y) [Negate] / \
Variable(y) [Negation] / \
| / Variable(v)
Constant(2.345) /
/
[Subtract]
[Subtraction]
____/ \____
/ \
Variable(w) Constant(7.3)
@ -809,7 +857,8 @@ int main()
typedef exprtk::parser<double> parser_t;
typedef exprtk::parser_error::type error_t;
std::string expression_str = "z := 2 myfunc([4+sin(x/pi)^3],y^2)";
std::string expression_str =
"z := 2 myfunc([4 + sin(x / pi)^3],y ^ 2)";
double x = 1.1;
double y = 2.2;