add basic number reader (no compound numbers yet)
This commit is contained in:
commit
798f70a2e9
303
read.scm
303
read.scm
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@ -54,6 +54,16 @@
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(lambda ()
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(read-char port))))
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(define string->read-function
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(lambda (str)
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(let ((i -1)
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(length (string-length str)))
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(lambda ()
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(set! i (+ i 1))
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(if (>= i length)
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#f
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(string-ref str i))))))
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;;; READ:
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;;;
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;;; Stream readers contain mutable state. This is the case-folding mode
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@ -67,9 +77,13 @@
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;;; (FOLD-CASE?): Returns a boolean if case folding is enabled.
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;;; (FOLD-CASE! BOOL): Sets the case folding to BOOL.
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(define port->read
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(lambda (read-function filename)
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(let ((line-number 1)
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(offset 0)
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(lambda (read-function filename . location)
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(let ((line-number (if (null? location)
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1
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(car location)))
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(offset (if (null? location)
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0
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(cadr location)))
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(pushback-buffer '())
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(datum-labels '())
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(fold-case? #f))
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@ -141,6 +155,11 @@
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(else (error 'read->port 'invalid (cons op args)))))))
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port))))
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(define ident->read
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(lambda (location ident)
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(apply port->read (string->read-function (ident 'value))
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location)))
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;;; ;;;;;;;;;;;;;;
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;;; Character maps
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;;; ;;;;;;;;;;;;;;
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@ -180,6 +199,7 @@
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;;; An "action" is a procedure that takes four arguments:
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;;;
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;;; TABLE: The current table.
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;;; CHAR: The character that was matched against the CHARMAP in TABLE.
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;;; ACC: An arbitrary "accumulator" value that is different depending
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;;; on the readtable in question.
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@ -210,18 +230,16 @@
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;;; Return a new readtable where CHAR is bound to ACTION.
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(define readtable:update
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(lambda (table char action)
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(readtable:new (%readtable:default-action table)
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(car (charmap:insert
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(%readtable:charmap table) char action)))))
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;;; Update TABLE to act on all characters in LST with ACTION.
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(define readtable:update-list
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(lambda (table lst action)
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(fold (lambda (char table)
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(readtable:update table char action))
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table
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lst)))
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(lambda (table chars action)
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(let ((chars (if (pair? chars)
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chars
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(list chars))))
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(fold (lambda (char table)
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(readtable:new (%readtable:default-action table)
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(car (charmap:insert
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(%readtable:charmap table) char action))))
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table
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chars))))
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;;; Construct new readtable with no characters in its map and
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;;; DEFAULT-ACTION as the default action.
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@ -392,7 +410,7 @@
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(readtable:empty/default (readtable:error
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'read-improper-cdr
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"improper list has 1 cdr"))
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(list readtable:update-list
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(list readtable:update
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readtable:ASCII-whitespace
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readtable:skip)
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(list readtable:update %eol
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@ -458,6 +476,236 @@
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(error 'expect-port-list 'no-list-found)
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(readtable:read-proper-list table port))))
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;;; ;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Implementation of a Pratt parser. In a Pratt parser, all tokens are
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;;; "operators" with "precedence".
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;;;
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;;; Since Pratt parsers are implemented in terms of procedures, they can
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;;; parse any grammar.
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;;;
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;;; This file implements the algorithm found in:
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;;;
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;;; van de Vanter, Michael L. "A Formalization and Correctness Proof of
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;;; the CGOL Language System." (Master's Thesis). MIT Laboratory for
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;;; Computer Science Technical Report MIT-LCS-TR-147 (Cambridge,
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;;; Massachusetts). 1975. https://hdl.handle.net/1721.1/149442.
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;;; (PRATT:OPERATOR PRECEDENCE PROCEDURE)
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;;; constructs a description of an operator.
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;;;
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;;; PRECEDENCE is an exact number describing the precedence of the
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;;; operator, and for portability should only be an integer.
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;;;
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;;; (The special EOF operator, which always exists, has negative
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;;; infinity precedence.)
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;;;
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;;; PROCEDURE is of the form (PROCEDURE OPERATORS LEFT TOKEN READER).
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;;; OPERATORS is the operators map.
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;;; LEFT is a PRATT:TOKEN, which was to the left of the operator.
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;;; TOKEN is the token read from the reader wit the same type.
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;;; READER is a reader object.
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;;;
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;;; PROCEDURE consumes tokens to obtain the
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;;; right hand side of its expression. PROCEDURE produces a PRATT:TOKEN.
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(define pratt:operator cons)
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(define pratt:precedence car)
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(define pratt:procedure cdr)
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(define pratt:search-token
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(lambda (operators token)
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(smap:search operators (symbol->string (token 'type)))))
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;;; Parse a stream from READER, where the precedence limit is specified as
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;;; BINDING-POWER. If BINDING-POWER is #F, then there is no precedence
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;;; limit. Operators are read from OPERATORS, which is a SMAP.
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(define pratt
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(lambda (operators binding-power reader)
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(letrec
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((loop
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(lambda (left)
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(let ((token (reader 'peek)))
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(let ((operator (pratt:search-token operators token)))
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(if (null? next-operator)
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(error 'pratt 'unknown-operator token
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operators binding-power reader))
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(if (and binding-power
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(>= (pratt:precedence operator)
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binding-power))
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left
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(parse operator left (reader 'read) reader))))))
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(parse
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(lambda (operator left token reader)
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(loop ((pratt:procedure operator)
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operators
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left
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token
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reader)))))
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;; Read the first token.
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(let ((token (reader 'read)))
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(let ((operator (pratt:search-token operators token)))
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(if (null? operator)
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(error 'pratt 'unknown-operator token
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operators binding-power reader))
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(parse operator #f token reader))))))
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;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Math reader.
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;;;
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;;; Scheme numbers are a kludge. A proper LISP would either represent
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;;; numbers as
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;;;
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;;; (+ 4 (*i 6)) or (@ (. 12 34) 2) or (e 12 3) etc.
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;;;
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;;; or just bite the bullet and include a full infix expression parser.
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;;;
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;;; This is a full infix expression parser. It will parse expressions
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;;; such as SIN(X) or X * 5I/6. Identifiers and functions are any Scheme
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;;; object.
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;;;
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;;; The math reader can be invoked using #MATH(expr). EXPR is an infix
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;;; mathematical expression. #PREFIX(expr) reads EXPR in the normal
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;;; reader. All other hash identifiers are unsupported in #MATH.
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;;; The basic number reader. The basic syntax is
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;;;
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;;; PREFIXES* SIGN? (RADIX+ ("." RADIX+)? | "." RADIX+) ("e" RADIX+)? "i"?
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;;; Prefixes are handled by the "#" reader.
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;;; Incremental builder for a number, driven by the lexer.
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;;; TODO: how will this be turned into a number, in the end?
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(define read:number-builder
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(lambda (radix-table)
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(let ((main '())
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(decimal '())
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(exp-char #f)
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(exp-digits '())
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(imaginary? #f)
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(current-part 'main)
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(exactness #f))
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(let ((append-part
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(lambda (char)
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(cond
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((eq? current-part 'main)
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(set! main (cons char main)))
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((eq? current-part 'decimal)
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(set! decimal (cons char decimal)))
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((eq? current-part 'exp)
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(set! exp-digits (cons char exp-digits)))))))
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(lambda (op . args)
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(cond
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((eq? op 'finalize)
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(if (not exactness)
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(set! exactness 'exact))
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(list 'number-builder
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main exactness decimal exp-char exp-digits imaginary?))
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((eq? op 'exactness!) (set! exactness (car args)))
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((eq? op 'radix-table!) (set! radix-table (car args)))
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((eq? op 'set-imaginary!)
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(set! imaginary? #t))
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((eq? op 'set-decimal!)
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(if (not exactness)
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(set! exactness 'inexact))
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;;
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(if (not (eq? current-part 'main))
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(error 'number-builder "cannot set to decimal" current-part)
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(set! current-part 'decimal)))
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((eq? op 'set-exponential!)
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(if (not exactness)
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(set! exactness 'inexact))
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;;
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(if (eq? current-part 'exp)
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(error 'number-builder "cannot set to exponential"))
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(set! current-part 'exp)
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(set! exp-char (car args)))
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;;
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((eq? op 'radix-table) radix-table)
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(else (append-part op))))))))
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(define readtable:return-number
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(lambda (_ char acc port)
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(port 'push char)
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(acc 'finalize)))
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;;; Main lexer for number table.
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(define readtable:number-main-table
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(readtable:process
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(readtable:empty/default readtable:return-number)
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(list readtable:update #\.
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(lambda (table char number-builder port)
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(number-builder 'set-decimal!)
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(readtable:next table
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number-builder
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port)))
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(list readtable:update (list #\e #\s #\f #\d #\l)
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(lambda (table char number-builder port)
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(number-builder 'set-exponential! char)
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(readtable:next table
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number-builder
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port)))
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(list readtable:update #\_ readtable:skip)
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(list readtable:update #\i
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(lambda (table char number-builder port)
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(number-builder 'set-imaginary!)
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(number-builder 'finalize)))))
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;;; Generate a lexer given a list of numbers in the radix.
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(define readtable:for-radix
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(lambda (radix-list)
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(readtable:process
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readtable:number-main-table
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(list readtable:update radix-list
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(lambda (table char number-builder port)
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(number-builder char)
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(readtable:next table number-builder port))))))
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(define readtable:for-bin
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(readtable:for-radix '(#\0 #\1)))
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(define readtable:for-oct
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(readtable:for-radix '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7)))
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(define readtable:for-dec
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(readtable:for-radix '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9)))
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(define readtable:for-hex
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(readtable:for-radix '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
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#\a #\b #\c #\d #\e #\f)))
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;;; Read the sign at the start of a number.
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(define readtable:read-sign
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(readtable:process
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(readtable:empty/default
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(lambda (_ char number-builder port)
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(readtable:act (number-builder 'radix-table)
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char
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number-builder
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port)))
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(list readtable:update (list #\+ #\-)
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(lambda (_ char number-builder port)
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(number-builder 'sign! char)
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(readtable:next (number-builder 'radix-table)
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number-builder
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port)))
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(list readtable:update #\_ readtable:skip)))
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(define readtable:read-prefix-char
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(let ((act (lambda args
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(lambda (_ char number-builder port)
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(apply number-builder args)
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(readtable:next readtable:read-number-prefix
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number-builder
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port)))))
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(readtable:process
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(readtable:empty/default (readtable:error "invalid prefix"))
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(list readtable:update #\i (act 'exactness! 'inexact))
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(list readtable:update #\e (act 'exactness! 'exact))
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(list readtable:update #\b (act 'radix-table! readtable:for-bin))
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(list readtable:update #\o (act 'radix-table! readtable:for-oct))
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(list readtable:update #\d (act 'radix-table! readtable:for-dec))
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(list readtable:update #\x (act 'radix-table! readtable:for-hex)))))
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(define readtable:read-number-prefix
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(readtable:process
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(readtable:empty/default (readtable:jump readtable:read-sign))
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(list readtable:update #\# (readtable:jump/next readtable:read-prefix-char))))
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;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Reader for stuff that start with "#"
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;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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@ -559,7 +807,7 @@
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(readtable:process
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(readtable:empty/default (readtable:error 'datum-label-next
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"invalid datum label/ref"))
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(list readtable:update-list readtable:digits readtable:push-char)
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(list readtable:update readtable:digits readtable:push-char)
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(list readtable:update #\=
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(lambda (_ __ acc port)
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(acc 'finalize->ident)
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@ -631,10 +879,12 @@
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(let ((ident (readtable:read-ident #f char #f port)))
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(let ((container (smap:search read:hash-messages
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(ident 'value))))
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;; TODO: check if the hash message starts a number.
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(if (null? container)
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(error 'read-hash-messages 'unknown-constant
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(ident 'value))
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(let ((number-port (ident->read (port 'location) ident)))
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(number-port 'fold-case! #t)
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(readtable:next readtable:read-prefix-char
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(read:number-builder readtable:for-dec)
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number-port))
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((map:val container) acc port))))))
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;;; ;;;;;;;;;;;;;;;;;;;;;;
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@ -676,12 +926,12 @@
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(define readtable:hash
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(readtable:process
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(readtable:empty/default read:read-hash-messages)
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(list readtable:update-list readtable:ASCII-whitespace
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(list readtable:update readtable:ASCII-whitespace
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(readtable:error 'hash 'whitespace-after-hash))
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(list readtable:update #\| (readtable:jump/next readtable:block-comment))
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(list readtable:update #\; readtable:datum-comment)
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(list readtable:update #\\ readtable:character)
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(list readtable:update-list readtable:digits ; Datum labels
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(list readtable:update readtable:digits ; Datum labels
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(lambda (_ char toplevel port)
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(readtable:act readtable:datum-label-next
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char
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@ -698,7 +948,7 @@
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(lambda ()
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(readtable:process
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(readtable:empty/default readtable:read-ident)
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(list readtable:update-list readtable:ASCII-whitespace readtable:skip)
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(list readtable:update readtable:ASCII-whitespace readtable:skip)
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(list readtable:update #f (readtable:return 'eof))
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(list readtable:update %bol readtable:read-list)
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(list readtable:update %eol (readtable:error 'top "unbalanced list"))
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@ -794,3 +1044,10 @@
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(read-all "#u8(x y z w)")
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(read-all "#\\newline")
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(read-all "#\\a")
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(read-all "#b11")
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(read-all "#XFF")
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(read-all "#i#x10")
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(read-all "#d1234.5678")
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(read-all "#e10.5")
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(read-all "#d10.24f12")
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