Add section to README about functions

README.md

@@ -30,6 +30,7 @@ The currently available opcodes are as follows:
 - `p` - print out the arguments: `pHello World!` prints "Hello World!"
 - `a`, `s`, `m`, `d` - add, subtract, multiply, and divide, respectively: `a2-2` adds 2 + 2.
 - `l` - declare a variable: `lv9` declares variable `v` with value `9`; doing `p$v` prints out 9.
+- `f` - declare a function: see [Functions](#make-a-pull-request) for more info
 - `#` - comment: the interpreter will skip this line.
 
 Here's an example "Hello world" program:
@@ -40,6 +41,31 @@ lwWorld!
 p$h $w
 ```
 
+### Functions
+
+*functions* are ways to "pipe" math output to another operation. For example, you could assign the output to a variable, like below:
+
+```
+#Declare a function
+fxa3-3
+#Call the function and assign it to variable
+lv*x
+#will print out 6
+p$v
+```
+
+Or you could print it out directly:
+
+```
+#Declare a function
+fxs30-3
+#Call it and print it out
+#Will print out 27
+p*x
+```
+
+Read [the devlog entry for more](https:/tilde.team/~karx/blog/sandwich-devlog-3-function-junction.html) info.
+
 ## Contributing
 
 
@@ -63,10 +89,11 @@ Read [this guide](https://git-send-email.io) for more information.
 
 ## TODO
 
-- [x] Better documentation
+
 - [ ] Ability to explicitly print math output and assign math output to variables
-- [x] Add support for comments (should be pretty easy)
-- [x] Unit testing and CI/CD
+- [ ] Better function parsing (multi-instruction functions?)
+- [ ] Importing/Running other files
+- [ ] "Verbose" or "Debug" mode (environment variable or flag?)
 
 ## License