README.md

Very simple interpretation and translation to intermediate code

Chapter 2 introduces the distinction between interpreters and compilers, and demonstrates some concepts of compilation, using the simple expression language as an example. Some concepts of interpretation are illustrated also, using a stack machine as an example.

Folder Intcomp contains the files used in Chapter 2.

A. Opening the Postscript files depends on operating system.

On Linux and MacOS, when Ghostscript and display are available:

gs prog.ps

will compute and show the result in a separate window.

Otherwise, use Ghostscript (install it if necessary) to convert the Postscript file to PDF:

gs -sDEVICE=pdfwrite -dNOPAUSE -dBATCH -sOutputFile=prog.pdf prog.ps

and then open the prog.pdf file with a PDF viewer.

Otherwise, on MacOS the free PDF reader Skim can convert Postscript to PDF and open the file: Skim > File > Open > select .ps file.

On Windows, one can install Ghostscript and GSview, then open the Postscript file with GSview > File > Open > select .ps file.

The approaches above work for the other Postscript files prog.ps and sierpinski.eps also.

B. To use the simple interpreters and compilers in Intcomp1.fs

dotnet fsi Intcomp1.fs

open Intcomp1;;

eval e1 [];;
run e1;;

closedin e1 [];;
closed1 e1;;

subst e6 [("z", CstI 17)];;
subst e7s0 [("z", CstI 100)];;

freevars e1;;
closed2 e1;;
freevars e7s0;;
closed2 e7s0;;

tcomp e1 [];;
teval (tcomp e1 []) [];;
eval e1 [];;
teval (tcomp e1 []) [] = (eval e1 []);;

reval [RCstI 10; RCstI 17; RDup; RMul; RAdd] [];;
rcomp (Prim("+", Prim("*", CstI 2, CstI 3), CstI 4));;

eval e0 [];;
rcomp e0;;
reval (rcomp e0) [];;

eval e1 [];;
scomp e1 [];;
seval (scomp e1 []) [];;

#q;;

C. Compiling the simple byte code machine

javac Machine.java

To run the two build in instruction sequences rpn1 and rpn2 in the Main method

java Machine 
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