Add BLANK() function

Cargo.toml

@@ -8,7 +8,7 @@ license = "MIT OR Apache-2.0"
 name = "xlformula_engine"
 readme = "README.md"
 repository = "https://github.com/jiradaherbst/XLFormula-Engine"
-version = "0.4.2"
+version = "0.4.3"
 
 [dependencies]
 chrono = { version = "0.4.41", default-features = false }

src/calculate/operation/function.rs

@@ -142,6 +142,7 @@ where
         types::Function::Find => calculate_find(get_find_args(exp, f)),
         types::Function::Search => calculate_search(get_find_args(exp, f)),
         types::Function::IsError => calculate_iserror(get_unary_function_arg(exp, f)),
+        types::Function::Blank => types::Value::Blank,
     }
 }
 

src/grammar.pest

@@ -36,7 +36,7 @@ logical_operator = _{ equal | not_equal | greater_or_equal | greater
     greater_or_equal= { ">=" }
     less_or_equal   = { "<=" }
 
-function = _{ abs | sum | product | average | negate | days | year | month | day | right | left | iff | isblank | find | search | iserror | custom_function  }
+function = _{ abs | sum | product | average | negate | days | year | month | day | right | left | iff | isblank | find | search | iserror | blank_func | custom_function  }
     abs     = { ^"ABS" ~ "(" ~ expr ~ ")" }
     sum     = { ^"SUM" ~ function_param_with_atomic_expr}
     product = { ^"PRODUCT" ~ function_param_with_atomic_expr}
@@ -53,6 +53,7 @@ function = _{ abs | sum | product | average | negate | days | year | month | day
     find   = { ^"FIND" ~ function_param }
     search = { ^"SEARCH" ~ function_param }
     iserror = { ^"ISERROR" ~ function_param }
+    blank_func = { ^"BLANK" ~ empty_param }
     custom_function = { reference ~ (function_param | empty_param) } 
 
 logical_function = _{ or | and | xor | not } 

src/parse_formula.rs

@@ -125,6 +125,14 @@ where
     types::Formula::Operation(operation)
 }
 
+fn build_formula_blank_func<N>() -> types::Formula<N>
+where
+    N: XlNum,
+    <N as FromStr>::Err: Debug,
+{
+    types::Formula::Value(types::Value::Blank)
+}
+
 fn build_formula_reference<N>(pair: pest::iterators::Pair<Rule>) -> types::Formula<N>
 where
     N: XlNum,
@@ -197,6 +205,7 @@ fn rule_to_function_operator(collective_operation: Rule) -> types::Operator {
         Rule::find => types::Operator::Function(types::Function::Find),
         Rule::search => types::Operator::Function(types::Function::Search),
         Rule::iserror => types::Operator::Function(types::Function::IsError),
+        Rule::blank_func => types::Operator::Function(types::Function::Blank),
         _ => unreachable!(),
     }
 }
@@ -410,6 +419,7 @@ where
             Rule::find => build_formula_collective_operator(Rule::find, pair, f),
             Rule::search => build_formula_collective_operator(Rule::search, pair, f),
             Rule::iserror => build_formula_collective_operator(Rule::iserror, pair, f),
+            Rule::blank_func => build_formula_blank_func(),
             _ => unreachable!(),
         })
         .map_infix(

src/types.rs

@@ -4,6 +4,7 @@ use std::{
     fmt::{Debug, Display},
     str::FromStr,
 };
+
 /// Defines Excel Functions.
 #[derive(Debug, Copy, Clone)]
 pub enum Function {
@@ -27,6 +28,7 @@ pub enum Function {
     Find,
     Search,
     IsError,
+    Blank,
 }
 
 /// Defines Excel Operators.

tests/test.rs

@@ -468,6 +468,13 @@ fn it_evaluate_wrong_parens1() {
     test_all_types!(evaluate_formula_string, "=Hello World", "#PARSE!");
 }
 
+//////////////////////////// Blank //////////////////////////////////
+
+#[test]
+fn it_evaluate_blank() {
+    test_all_types!(evaluate_formula_string, "=BLANK()", "0");
+}
+
 //////////////////////////// Boolean //////////////////////////////////
 #[test]
 fn it_evaluate_comparison_operators() {