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\ This is a sample file which can be interpretered with our forth.

\

\ As you can surmise comments start with a backslash and last until the end of the line.

\

\ Square a number

: SQUARE dup * ;

\ Calculate a factorial of the given number

: FACT DUP 1 > if DUP 1 - FACT * THEN ;

\ Output a single star

: STAR 42 EMIT ;

\ Output N stars

: stars 0 do star loop cr ;

\ Test this

1 stars

2 stars

3 stars

4 stars

5 stars

4 stars

3 stars

2 stars

1 stars

\

\ We can only use DO..LOOP within a word, so we define a word to show factorials.

\

: FACTS

20 0 DO

I DUP . SPACE FACT . CR

LOOP ;

\

\ Now invoke that word to show things work

\

." Showing factorials " CR

FACTS

." Showing variables work, set x = 5, and print it:"

VARIABLE x

5 x ! x @ .

CR

\

\ A few more common primitives.

\

." Showing some more arithmetic words:" CR

-5 NEGATE . 5 NEGATE . CR

5 1+ . 5 1- . CR

-7 ABS . 7 ABS . CR

3 9 MIN . 3 9 MAX . CR

1 2 2DUP + . . . CR

." Showing CONSTANT:" CR

42 CONSTANT answer

answer . answer answer + . CR