Sympy：来自逻辑表达式的C代码

Question

From a sympy logical expression, I would like to get the equivalent C code. First off, I noticed that you cannot use the native logical operators like and and or because sympy somehow strips them off. Fair enough, there's & and friends . I tried

from sympy import *
from sympy.utilities.codegen import codegen

x = Symbol('x')
is_valid = Symbol('is_valid')

# f = x > 0 and is_valid  # TypeError: cannot determine truth value of
f = (x > 0) & is_valid  # And(is_valid, x > 0)

# TypeError: The first argument must be a sympy expression.
[(c_name, c_code), (h_name, c_header)] = codegen(("f", f), "C")

but for some reason, I'm getting

TypeError: The first argument must be a sympy expression.

Any hints?

Answer 1

The error message is based on a hard-coded isinstance check. If it is removed, I get

#include "f.h"
#include <math.h>

double f(double is_valid, double x) {

   double f_result;
   f_result = is_valid && x > 0;
   return f_result;

}

Note however that this is still probably not what you want, since is_valid is set as a double, and you probably want it to be an int (or C99 bool).

My suggestion: use ccode on your expression directly, and write the function wrapper manually. You could also use pycodeexport if you need something more scalable.