44 lines
1.8 KiB
CoffeeScript
44 lines
1.8 KiB
CoffeeScript
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lispeval = require './eval'
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{cons, nil, nilp, car, cdr, listToVector} = require './lists'
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module.exports =
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create_vm_expression_evaluator: (defining_scope, params, body) ->
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(cells, scope) ->
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args = (amap = (cells, accum) ->
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return accum if nilp cells
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amap((cdr cells), accum.concat(lispeval (car cells), scope)))(cells, [])
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body.apply null, args
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create_lisp_expression_evaluator: (defining_scope, params, body) ->
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(cells, scope) ->
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# Takes the current scope, which has been passed in during the
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# execution phase, and evaluate the contents of the parameters
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# in the context in which this call is made (i.e. when the
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# function is *called*, rather than defined.
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new_scope = (cmap = (cells, params, nscope) ->
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return nscope if (nilp cells) or (nilp params)
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nscope[(car params)] = lispeval (car cells), scope
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cmap((cdr cells), (cdr params), nscope))(cells, params, {})
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# Execute and evaluate the body, creating an inner scope that
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# consists of: (1) the bound variables (the parameters)
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# evaluated in the context of the function call, because that's
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# where they were encountered (2) the free variables evaluated
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# in the context of the defining scope, because that's where
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# *they* were encountered.
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#
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# While this inspiration comes from Coglan, the clearest
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# explanation is from Lisperator's 'make_lambda' paragraph at
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# http://lisperator.net/pltut/eval1/
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inner_scope = cons(new_scope, defining_scope)
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(nval = (body, memo) ->
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return memo if nilp body
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nval((cdr body), lispeval((car body), inner_scope)))(body)
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create_special_form_evaluator: (defining_scope, params, body) ->
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(cells, scope) -> body(cells, scope)
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