Running commands from string

Question

I have a string:

string s="digitalWrite(8,LOW);"

Is there any way to run it as a code?

• chrisl: Not an easy way, since you basically would need to write a C/C++ interpreter library for this. I don't know of such a library. Why do you need to do this? What are you trying to achieve?
• rktech: To run commands that will be saved in external eeprom
• chrisl: Do you really have such complex programs to save there, that you need C syntax text there? Instead you could build your own command structure, which can be way easier to interpret. What commands do you need to save in the EEPROM?
• rktech: @chrisl thank you, I forgot that I can do it like this

Answer 1

This is actually pretty simple:

if (s == "digitalWrite(8,LOW);") {
 digitalWrite(8,LOW);
}

Obviously, it will not work is s contains any other string... If you want something more general, that is able to interpret a wide range of possible commands, you will have to define a language, and write an interpreter for that language. From the example you give, it seems you would like your language to look like C++. This is most likely a bad design choice. If you want an interpreter that understands the whole C++ language: forget it. You will never fit something this big into an Arduino Uno.

Here is, for inspiration, a very simple interpreter I wrote that understand the following commands:

mode <pin> <mode>: pinMode()
read <pin>: digitalRead()
aread <pin>: analogRead()
write <pin> <value>: digitalWrite()
awrite <pin> <value>: analogWrite()
echo <value>: set echo off (0) or on (1)

You can use it a basis for writing your custom interpreter. Otherwise you can do a Web search for "Arduino interpreter": you should be able to find interpreters implementing a wide variety of languages, including compact binary languages (Firmata), Forth (another one), Lisp, Basic, and even a C-like language.