"±" Signed conditional and "abs" post_procs

docs/participate/adding-decoders.md

@@ -315,6 +315,7 @@ Valid operations are:
 - "*" multiply
 - "+" add
 - "-" subtract
+- "±" signed conditional add or subtract
 - "%" modulo
 - "<" shift left
 - ">" shift right
@@ -323,6 +324,7 @@ Valid operations are:
 - "^" Logical XOR the values
 - "min" the minimum allowed value
 - "max" the maximum allowed value
+- "abs" absolute value
 
 `lookup` This specifies a lookup table for any decoded "string_from_hex_data" string. If the string is defined in the table its related string will be assigned to the property. If no matching hex string is present the property is defined as not decoded. 
 

src/decoder.cpp

@@ -743,7 +743,15 @@ int TheengsDecoder::decodeBLEJson(JsonObject& jsondata) {
                     if (temp_val < post_proc[i + 1].as<double>()) {
                       temp_val = post_proc[i + 1].as<double>();
                     }
-                  }
+                  } else if (strncmp(post_proc[i].as<const char*>(), "±", 1) == 0) {
+                    if (temp_val < 0) {
+                      temp_val += post_proc[i + 1].as<double>();
+                    } else {
+                      temp_val -= post_proc[i + 1].as<double>();
+                    }
+                  } else if (strncmp(post_proc[i].as<const char*>(), "abs", 3) == 0) {
+                      temp_val = abs(temp_val);
+                  } 
                 }
               }
             }