Function expr_batch_add_expression_function 

#[unsafe(no_mangle)]
pub extern "C" fn expr_batch_add_expression_function(
    batch: *mut ExprBatch,
    name: *const c_char,
    params: *const c_char,
    expression: *const c_char,
) -> i32

Add an expression function to a batch

Expression functions are mathematical expressions that can call other functions. They are specific to this batch and take precedence over context functions.

Parameters

• batch: The batch
• name: Function name (must be valid UTF-8)
• params: Comma-separated parameter names (e.g., “x,y,z”)
• expression: The expression string defining the function

Returns

0 on success, non-zero on error