Fixing parsing of numbers in mexpr mode.

README.md

@@ -130,7 +130,34 @@ You will require to have [Leiningen](https://leiningen.org/) installed.
 
 This will start a Lisp 1.5 read/eval/print loop (REPL).
 
-To end a session, type `quit` at the command prompt.
+Command line arguments are as follows:
+
+```
+  -f FILEPATH, --file-path FILEPATH                         Set the path to the directory for reading and writing Lisp files.
+  -h, --help
+  -p PROMPT, --prompt PROMPT         Sprecan::              Set the REPL prompt to PROMPT
+  -r INITFILE, --read INITFILE       resources/lisp1.5.lsp  Read Lisp system from file INITFILE
+  -s, --strict                                              Strictly interpret the Lisp 1.5 language, without extensions.
+  -t, --trace                                               Trace Lisp evaluation.
+```
+
+To end a session, type `STOP` at the command prompt.
+
+### Input/output
+
+Lisp 1.5 greatly predates modern computers. It had a facility to print to a line printer, or to punch cards on a punch-card machine, and it had a facility to read system images in from tape; but there's no file I/O as we would currently understand it, and, because there are no character strings and the valid characters within an atom are limited, it isn't easy to compose a sensible filename.
+
+I've provided two functions to work around this problem.
+
+#### SYSOUT
+
+`SYSOUT` dumps the global object list to disk as a single S Expression (specifically: an association list). This allows you to persist your session, with all your current work, to disk. The function takes one argument, expected to be a symbol, and, if that argument is provided, writes a file whose name is that symbol with `.lsp` appended. If no argument is provided, it will construct a filename comprising the token `Sysout`, followed by the current date, followed by `.lsp`. In either case the file will be written to the directory given in the FILEPATH argument at startup time, or by default the current directory.
+
+Obviously, `SYSOUT` may be called interactively (and this is the expected practice).
+
+#### SYSIN
+
+`SYSIN` reads a file from disk and overwrites the global object list with its contents. The expected practice is that this will be a file created by `SYSOUT`. A command line flag `--read` is provided so that you can specify   
 
 ## Learning Lisp 1.5
 

resources/lisp1.5.lsp

@@ -5,7 +5,7 @@
 ;; it to NIL
 (F . NIL)
 ;; Binding all system functions to NIL so that you can see on the OBLIST that
-;; they exist
+;; they exist.
 (ADD1 . NIL)
 (APPEND . NIL)
 (APPLY . NIL)
@@ -25,6 +25,7 @@
 (PLUS . NIL)
 (PRETTY . NIL)
 (QUOTIENT . NIL)
+(READ . NIL)
 (REMAINDER)
 (RPLACA . NIL)
 (RPLACD . NIL)

src/beowulf/bootstrap.clj

@@ -16,7 +16,8 @@
             [beowulf.host :refer [ADD1 DIFFERENCE FIXP NUMBERP PLUS QUOTIENT
                                   REMAINDER RPLACA RPLACD SUB1 TIMES]]
             [beowulf.io :refer [SYSIN SYSOUT]]
-            [beowulf.oblist :refer [*options* oblist NIL]])
+            [beowulf.oblist :refer [*options* oblist NIL]]
+            [beowulf.read :refer [READ]])
   (:import [beowulf.cons_cell ConsCell]
            [clojure.lang Symbol]))
 
@@ -411,6 +412,7 @@
         PLUS (apply PLUS args)
         PRETTY (apply pretty-print args)
         QUOTIENT (apply QUOTIENT args)
+        READ (READ)
         REMAINDER (apply REMAINDER args)
         RPLACA (apply RPLACA args)
         RPLACD (apply RPLACD args)

src/beowulf/reader/generate.clj

@@ -174,7 +174,6 @@
      (if
       (coll? p)
        (case (first p)
-         ">" 'GREATERP
          :λ "LAMBDA"
          :λexpr (make-cons-cell
                  (generate (nth p 1))
@@ -184,6 +183,7 @@
          :atom (symbol (second p))
          :bindings (generate (second p))
          :body (make-beowulf-list (map generate (rest p)))
+         (:coefficient :exponent) (generate (second p))
          :cond (gen-cond p)
          :cond-clause (gen-cond-clause p)
          (:decimal :integer) (read-string (strip-leading-zeros (second p)))
@@ -191,7 +191,6 @@
          :dotted-pair (make-cons-cell
                        (generate (nth p 1))
                        (generate (nth p 2)))
-         :exponent (generate (second p))
          :fncall (gen-fn-call p)
          :iexpr (gen-iexpr p)
          :iop (case (second p)
@@ -212,7 +211,7 @@
                   (list 'QUOTE (symbol (upper-case (second p)))))
          :mvar (symbol (upper-case (second p)))
          :octal (let [n (read-string (strip-leading-zeros (second p) "0"))
-                      scale (generate (nth p 2))]
+                      scale (generate (nth p 3))]
                   (* n (expt 8 scale)))
 
       ;; the quote read macro (which probably didn't exist in Lisp 1.5, but...)
@@ -221,7 +220,7 @@
                         (empty? (second p)) 0
                         (read-string (strip-leading-zeros (second p))))
          :scientific (let [n (generate (second p))
-                           exponent (generate (nth p 2))]
+                           exponent (generate (nth p 3))]
                        (* n (expt 10 exponent)))
 
       ;; default

src/beowulf/reader/parser.clj

@@ -78,7 +78,7 @@
       integer := #'-?[1-9][0-9]*';
       decimal := #'-?[1-9][0-9]*\\.?[0-9]*' | #'0.[0-9]*';
       scientific := coefficient e exponent;
-      coefficient := decimal;
+      coefficient := integer | decimal;
       exponent := integer;
       e := 'E';
       octal := #'[+-]?[0-7]+{1,12}' q scale-factor;

test/beowulf/mexpr_test.clj

@@ -42,11 +42,16 @@
     ;; Wrapping in a function call puts us into mexpr contest;
     ;; "T" would be interpreted as a sexpr, which would not be
     ;; quoted.
-    (let [expected "(ATOM A)"
+    (let [expected "(ATOM (QUOTE A))"
           actual (print-str (gsp "atom[A]"))]
       (is (= actual expected)))
+    (let [expected "(ATOM A)"
+          actual (print-str (gsp "atom[a]"))]
+      (is (= actual expected)))
+
     ;; I'm not clear how `car[(A B C)]` should be translated, but
     ;; I suspect as (CAR (LIST A B C)).
+
     (let [expected "(CAR (LIST A B C))"
           actual (print-str (gsp "car[(A B C)]"))]
       (is (= actual expected)))
@@ -63,10 +68,10 @@
 
 (deftest conditional-tests
   (testing "Conditional expressions"
-    (let [expected "(COND ((ATOM X) X) (T (FF (CAR X))))"
+    (let [expected "(COND ((ATOM X) X) ((QUOTE T) (FF (CAR X))))"
           actual (print-str (gsp "[atom[x]->x; T->ff[car[x]]]"))]
       (is (= actual expected)))
-    (let [expected "(LABEL FF (LAMBDA (X) (COND ((ATOM X) X) (T (FF (CAR X))))))"
+    (let [expected "(LABEL FF (LAMBDA (X) (COND ((ATOM X) X) ((QUOTE T) (FF (CAR X))))))"
           actual (print-str
                    (generate
                      (simplify
@@ -83,6 +88,6 @@
 
 (deftest assignment-tests
   (testing "Function assignment"
-    (let [expected "(SET (QUOTE FF) (QUOTE (LAMBDA (X) (COND ((ATOM X) X) (T (FF (CAR X)))))))"
+    (let [expected "(SET (QUOTE FF) (QUOTE (LAMBDA (X) (COND ((ATOM X) X) ((QUOTE T) (FF (CAR X)))))))"
           actual (print-str (gsp "ff[x]=[atom[x] -> x; T -> ff[car[x]]]"))]
       (is (= actual expected)))))