Forth Lesson 3

Review

In the previous lesson we learned that:

• Forth words are described by stack diagrams like: ( argn .. arg0 -- resultm .. result0 )
• Comments are either ( this is a comment ) or \ the rest of the line is a comment
• Both "(" and "\" must be followed by whitespace
• Comments work by executing a word that then explicitly calls the input parser

Arithmetic and Logical Operators

We have already seen " ", which pops two numbers, adds them, and pushes the result. Here are some more numeric operators with their stack diagrams:

         ( n1 n2 -- n1 n2 )
 -       ( n1 n2 -- n1-n2 )
 *       ( n1 n2 -- n1*n2 )   \ Signed multiplication
 /       ( n1 n2 -- n1/n2 )   \ Signed division
 mod     ( n1 n2 -- n1%n2 )
 /mod    ( n1 n2 -- n1%n2 n1/n2 )
 and     ( n1 n2 -- n1