Forth

MakoForth Reference Guide

MakoForth is a small Forth dialect which should be moderately familiar to anyone who has been exposed to ANS-Forth. The major notable differences are the use of # as line comments, loop...(break)...again|until|while looping constructs and the inclusion of syntax for inline double-quoted string constants. Cells are always 32-bit two's complement signed integers.

Conventions

• a,b and n are signed 32-bit numbers (or any value)
• str is the address of a null (0) terminated string
• f is a bit-flag- 0 for false and -1 for true
• addr generally refers to an address

Words with starred stack effects are immediate and will execute when encountered rather than being compiled.

Core Vocabulary

• + ( a b -- n ) add a to b
• - ( a b -- n ) subtract b from a
• * ( a b -- n ) multiply a by b
• / ( a b -- n ) divide a by b
• mod ( a b -- n ) compute the modulus of a by b
• and ( a b -- n ) bitwise and
• or ( a b -- n ) bitwise or
• xor ( a b -- n ) bitwise xor
• not ( a -- n ) bitwise not
• < ( a b -- f ) is a less than b?
• > ( a b -- f ) is a greater than b?
• ! ( n addr -- ) write value n to an address in memory
• @ ( addr -- n ) read a value from an address in memory
• dup ( a -- a a ) duplicate the top stack element
• over ( a b -- a b a ) duplicate the second stack element
• drop ( a -- ) discard the top stack element
• swap ( a b -- b a ) exchange the top stack elements
• >r ( n -- ) move the top stack element to the rstack
• r> ( -- n ) move the top rstack element to the stack
• i ( -- n ) copy the top rstack element to the stack
• j ( -- n ) copy the second rstack element to the stack
• here ( -- addr ) obtain the address of a var containing the end of the dictionary
• mode ( -- f ) obtain true if compiling, false if interpreting
• , ( n -- ) append a value to the dictionary and advance here
• ] ( -- ) switch to compiling mode
• [ ( -- )* switch to interpreting mode
• immediate ( -- ) make the last defined word immediate
• literal ( n -- )* compile a constant on the stack into the dictionary definition
• create ( -- ) read a name from the input stream and make a new dictionary entry
• exit ( -- )* compile a return but stay in compiling mode
• : ( -- ) essentially create ]- define a procedure
• ; ( -- )* terminate the current dictionary definition
• if ( -- )* compile an if (takes an argument from the stack)
• then ( -- )* complete an if statement.
• else ( -- )* place between if and then optionally
• loop ( -- )* create the head of a loop
• again ( -- )* complete a loop and branch back unconditionally
• while ( -- )* complete a loop and branch back if a stack value is true
• until ( -- )* complete a loop and branch back if a stack value is false
• break ( -- )* unconditionally exit the current loop
• ' ( -- )* compile a literal giving the address of a named word
• does> ( -- ) assign the remainder of this definition as behavior for the current word

Text Output

• . ( n -- ) print a signed number followed by a space
• space ( -- ) print a space
• cr ( -- ) print a carriage return
• type ( str -- ) print a string
• typeln ( str -- ) print a string and a carriage return

Programming Helpers

• forget ( -- ) read a name and forget it and all following words
• free ( -- ) print remaining free dictionary space
• see ( -- ) read a name and print a dissassembly of that word
• # ( -- )* ignore input until a newline- line comment
• ( ( -- )* ignore input until a )- block comment
• stack ( -- ) print the contents of the stack
• words ( -- ) print a list of all dictionary entries