Having looked into Forth (a bit)

...so I got a Forth interpreter and had a go. I didn't get much beyond beginner level, so take all I say with a pinch of salt.

Similarities

• Both have painful stack manipulation. This sucks.
• Both let you define your own instructions in terms of the existing primitives.

Differences

• Forth heap has named variables, Whitespace has numeric address.
• Whitespace can delve as far down the stack as you like. Forth can only look at the top 6 (I think) and even that gets convoluted.
• Forth looks (a bit) like a 3GL. Whitespace assembler looks like... assembler?
• Forth has function pointers (well, "word pointers" I suppose). I don't think that's possible in Whitespace.
• Forth word definitions are a bit like Whitespace assembler macros, but some stuff is executed when definitions are compiled. Not sure I grok'd this too well.

Not sure

• I said that Forth looks a bit like like a 3GL but feels a lot like assembler because it seems you are dealing with implementation details rather thn abstractions. But maybe that gets better is you have defined enough of your own words.