Difference between revisions of "Forth parser"
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The parser should create an "object" in memory like: | The parser should create an "object" in memory like: | ||
"lsl",0xF0,0xE0,0xC0,0xF1 | "lsl",0xF0,0xE0,0xC0,0xF1 | ||
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== Default opcode equivalency for forth words == | == Default opcode equivalency for forth words == | ||
Revision as of 17:13, 24 April 2018
Variable inference
Variables are stored locally on the return stack.
Any word that starts with ">" is a write to a variable.
For each word in function
If word starts with ">"
Add the word to an ordered list of unique words that starts with ">", remove the leading ">"
If there are more than 16 variables emit error
Emit STL #<index in the ordered list>
If word is in the list but does not start with ">"
Emit LDL #<index in the ordered list>
if there are more than 0 variables emit DIM #<largest index> as the first instruction of the function.
Example 1
: lsl for dup + next ; ( Simple complete function that implements left shift by repeated addition ) ":" this tells the parser to define a new function "lsl" is the name of the function Adr Value 0 0xF0 ( for ) 1 0xE0 ( dup ) 2 0xC0 ( add ) 3 0xF1 ( next ) ";" tells the parser that it has reached the end of the definition The parser should create an "object" in memory like: "lsl",0xF0,0xE0,0xC0,0xF1
Default opcode equivalency for forth words
Forth string - opcode + - add - - sub * - mul / - div
dup - dup
