47 lines
1.4 KiB
Scheme
47 lines
1.4 KiB
Scheme
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; Copyright (c) 1994 by Richard Kelsey. See file COPYING.
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; Eval'ing and type-checking code for primitives.
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(define-record-type primitive
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(id ; for debugging & making tables
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arg-predicates ; predicates for checking argument types
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eval ; evaluation function
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source ; close-compiled source (if any)
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expander ; convert call to one using primops
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expands-in-place? ; does the expander expand the definition in-line?
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inference-rule ; type inference rule
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)
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())
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(define make-primitive primitive-maker)
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(define-record-discloser type/primitive
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(lambda (primitive)
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(list 'primitive (primitive-id primitive))))
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(define (eval-primitive primitive args)
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(cond ((not (primitive? primitive))
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(user-error "error while evaluating: ~A is not a procedure" primitive))
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((args-okay? args (primitive-arg-predicates primitive))
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(apply (primitive-eval primitive) args))
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(else
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(user-error "error while evaluating: type error ~A"
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(cons (primitive-id primitive) args)))))
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; PREDICATES is a (possibly improper) list of predicates that should match
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; ARGS.
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(define (args-okay? args predicates)
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(cond ((atom? predicates)
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(if predicates
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(every? predicates args)
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#t))
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((null? args)
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#f)
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((car predicates)
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(and ((car predicates) (car args))
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(args-okay? (cdr args) (cdr predicates))))
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(else
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(args-okay? (cdr args) (cdr predicates)))))
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