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mirror of https://github.com/kanaka/mal.git synced 2024-10-27 06:40:14 +03:00
mal/impls/scheme/step2_eval.scm
Nicolas Boulenguez 033892777a Merge eval-ast and macro expansion into EVAL, add DEBUG-EVAL
See issue #587.
* Merge eval-ast and eval into a single conditional.
* Expand macros during the apply phase, removing lots of duplicate
  tests, and increasing the overall consistency by allowing the macro
  to be computed instead of referenced by name (`((defmacro! cond
  (...)))` is currently illegal for example).
* Print "EVAL: $ast" at the top of EVAL if DEBUG-EVAL exists in the
  MAL environment.
* Remove macroexpand and quasiquoteexpand special forms.
* Use pattern-matching style in process/step*.txt.

Unresolved issues:
c.2: unable to reproduce with gcc 11.12.0.
elm: the directory is unchanged.
groovy: sometimes fail, but not on each rebuild.
nasm: fails some new soft tests, but the issue is unreproducible when
  running the interpreter manually.
objpascal: unreproducible with fpc 3.2.2.
ocaml: unreproducible with 4.11.1.
perl6: unreproducible with rakudo 2021.09.

Unrelated changes:
Reduce diff betweens steps.
Prevent defmacro! from mutating functions: c forth logo miniMAL vb.
dart: fix recent errors and warnings
ocaml: remove metadata from symbols.

Improve the logo implementation.
Encapsulate all representation in types.lg and env.lg, unwrap numbers.
Replace some manual iterations with logo control structures.
Reduce the diff between steps.
Use native iteration in env_get and env_map
Rewrite the reader with less temporary strings.
Reduce the number of temporary lists (for example, reverse iteration
with butlast requires O(n^2) allocations).
It seems possible to remove a few exceptions: GC settings
(Dockerfile), NO_SELF_HOSTING (IMPLS.yml) and step5_EXCLUDES
(Makefile.impls) .
2024-08-05 11:40:49 -05:00

61 lines
1.7 KiB
Scheme

(import (scheme base))
(import (scheme write))
(import (lib util))
(import (lib reader))
(import (lib printer))
(import (lib types))
(define (READ input)
(read-str input))
(define (EVAL ast env)
; (display (str "EVAL: " (pr-str ast #t) "\n"))
(case (and (mal-object? ast) (mal-type ast))
((symbol)
(let ((key (mal-value ast)))
(or (alist-ref key env) (error (str "'" key "' not found")))))
((vector)
(mal-vector (vector-map (lambda (item) (EVAL item env))
(mal-value ast))))
((map)
(mal-map (alist-map (lambda (key value) (cons key (EVAL value env)))
(mal-value ast))))
((list)
(let ((items (mal-value ast)))
(if (null? items)
ast
(let ((op (EVAL (car items) env))
(ops (map (lambda (item) (EVAL item env)) (cdr items))))
(apply op ops)))))
(else ast)))
(define (PRINT ast)
(pr-str ast #t))
(define repl-env
`((+ . ,(lambda (a b) (mal-number (+ (mal-value a) (mal-value b)))))
(- . ,(lambda (a b) (mal-number (- (mal-value a) (mal-value b)))))
(* . ,(lambda (a b) (mal-number (* (mal-value a) (mal-value b)))))
(/ . ,(lambda (a b) (mal-number (/ (mal-value a) (mal-value b)))))))
(define (rep input)
(PRINT (EVAL (READ input) repl-env)))
(define (main)
(let loop ()
(let ((input (readline "user> ")))
(when input
(guard
(ex ((error-object? ex)
(when (not (memv 'empty-input (error-object-irritants ex)))
(display "[error] ")
(display (error-object-message ex))
(newline))))
(display (rep input))
(newline))
(loop))))
(newline))
(main)