Isis interpreter utilities Isis software documentation

Isis interpreter utilities

This document explains various utilities for interpreting Isis code, including loading libraries from files, memory buffers, and internet sites, as well as compiling Isis programs into a byte-code representation.

Loading programs and libraries

(load filename-or-url) # interpret isis code at the given location (load-compiled filename-or-url) # interpret compiled isis code at the given location (add-load-path path path ...) # add a directory to search for libraries in load interprets an Isis program or library from the given file name or URL. load-compiled interprets compiled Isis code (see below for information on how to compile programs and libraries). Both return the number of expressions that were evaulated. Otherwise an error message is printed and Null is returned if the source could not be found or opened.
-> (load "amazon.isis") 95 -> (load "macaroni.isis") 69 -> (load "kitchen.isis") ** load: file not found: kitchen.isis Null
When opening disk files, load and load-compiled will search particular directories for the file names you specify. After searching the current working directory, the directories named in the variable load-path-list are searched in order. You can use add-load-path to add your own directories to the load path. This may be useful if you have a directory full of Isis programs or libraries that may change location, or when you need to load files from an Isis process running in a different place in the file system.
-> load-path-list [ "/usr/local/isis/scripts" ] -> (add-load-path "/home/stefan/isis/scripts") [ "/usr/local/isis/scripts" "/home/stefan/isis/scripts" ]

Evaluating to and from strings

(eval string) # Evaluate first expression in string and return its value (uneval val val ...) # Convert values into a single string eval is a powerful operator that interprets the first expression in a given string and returns its value, or Null if no expression was found. If more than one expression is in the string, only the first expression is evaluated. Expressions are evaluated within the scope of the top-level environment.
-> (eval "3") 3 -> (eval "(+ 1 2 3 4 5)") 15 -> (eval "(set x 42)") 42 -> x 42
uneval performs the opposite operation. It converts one or more Isis values into a single string (like they would be printed). Any kind of value except for procedures may be converted.
-> (uneval 42) "42" -> (uneval "Convert me.") ""Convert me."" -> (uneval 89.56 [2 3 4] True 's') "89.560000 [ 2 3 4 ] True 's'" -> (eval (uneval 7)) 7 -> (uneval (eval "7")) "7"

Interpreting from various sources

(interactive) # interpret Isis code from the standard input port (interpret-port port) # interpret Isis code at the given input port (interpret-file filename) # interpret Isis code in the given file (interpret-url url) # interpret Isis code at the given url (interpret-http host portnum document) # interpret Isis code at the given http document (interpret-string string) # interpret Isis code in the given string (interpret-compiled-port port) # same as above, for compiled Isis code (interpret-compiled-file filename) (interpret-compiled-url url) (interpret-compiled-http host portnum document) (interpret-compiled-string string) The interactive primitive causes Isis to begin reading expressions directly from the standard input port (usually the keyboard). It is most useful as a way of beginning an interactive session with the user while interpreting an Isis program from a file or other source.

The other interpret- routines interpret Isis programs from various different sources. interpret-port is perhaps the most powerful, as it interprets Isis code from any input port, which could be connected to virtually any source (see the documentation on input and output ports for more information). The others interpret code from disk files, URLs, HTTP documents, or strings. The interpret-compiled- routines interpret compiled Isis programs. All of these routines return the total number expressions processed, or Null if the source could not be opened or found.

-> (interpret-file "/usr/local/isis/scripts/movie-utilities.isis") 37 -> (interpret-url "") I like traffic lights. 1

Compiling programs and libraries

(compile-port inport outport) # compile from an input port to an output port (compile-file infilename outfilename) # compile a disk file to another disk file These routines compile Isis programs into a fairly compact non-human-readable format. Once compiled, a program may be interpreted using load-compiled or one of the interpret-compiled- operators shown above. These routines return the total number of expressions compiled, or Null if an error occurred.
-> (compile-file "secret.isis" "secret.compiled.isis") 1 -> (load-compiled "secret.compiled.isis") I like traffic lights. 1

Real number precision

(set-precision significant-digits) # set precision of printed real numbers This routine sets the maximum number significant digits used when real numbers are printed by the interpreter. The default is 10. This routine only affects the printing of values, not their internal representation.
-> pi 3.141592654 -> (set-precision 3) 3 -> pi 3.14 -> (set-precision 15) 15 -> pi 3.14159265358979