Forth interpreter in Pharo Smalltalk
# small-forth
# Forth interpreter in Pharo Smalltalk.
## Introduction
For more see https://chicoary.wordpress.com/smallforth/.
SmallForth was developed based on the commands shown in the [Starting Forth book](https://www.forth.com/starting-forth/1-forth-stacks-dictionary/).
Forth words in upper case are accepted.
For example:
```Forth
7 dup DUP SWAP drop
```
its valid.
`SWAP` is the same as `swap` but `Swap` is not.
Strings are displayed in Pharo Smalltalk Transcript.
There is still no [REPL](https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop) available.
## Examples
The following example shows how to run a program written in Forth in the Pharo environment:
```Smalltalk
ForthInterpreter new eval: '1 2 dup'
```
To get the top of the parameter stack use `top`:
```Smalltalk
(ForthInterpreter new eval: '1 2 dup';top) >>> 2
```
To obtain the contents of the parameter stack use `stack`:
```Smalltalk
(ForthInterpreter new eval: '1 2 dup';stack) asArray >>> #(2 2 1)
```
Here is a more complex example (See [4. Decisions, Decisions…](https://www.forth.com/starting-forth/4-conditional-if-then-statements/) in Starting Forth):
```Smalltalk
example
| expr |
expr := ': egg-size
dup 18 < if ." reject " else
dup 21 < if ." small " else
dup 24 < if ." medium " else
dup 27 < if ." large " else
dup 30 < if ." extra large " else
." error "
then then then then then drop ;
{1} dup . egg-size'.
Transcript openIfNone.
Transcript clear.
ForthInterpreter new eval: (expr format: {
UIManager default request: 'Egg size?'
})
```