X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=a05b898f42660dfb9863508e218f1ff8db4a7390;hb=9e0ea182c4546eeefad63a27d63f057df3fb42c5;hp=cb02a3d785c826418445bb48cfe26ad41450b810;hpb=99ad1cc4097358554e04ed8c960a0793e9e5f968;p=scheme.forth.jl.git diff --git a/scheme.4th b/scheme.4th index cb02a3d..a05b898 100644 --- a/scheme.4th +++ b/scheme.4th @@ -4,6 +4,8 @@ scheme definitions include term-colours.4th include defer-is.4th +\ ------ Types ------ + 0 constant number-type 1 constant boolean-type 2 constant character-type @@ -11,10 +13,12 @@ include defer-is.4th 4 constant nil-type 5 constant pair-type 6 constant symbol-type -: istype? ( obj -- obj b ) +: istype? ( obj type -- obj bool ) over = ; -100 constant N +\ ------ Cons cell memory ------ + +1000 constant N create car-cells N allot create car-type-cells N allot create cdr-cells N allot @@ -46,6 +50,148 @@ variable nextfree cdr-type-cells + @ ; +: set-car! ( obj pair-obj -- ) + drop dup + rot swap car-type-cells + ! + car-cells + ! +; + +: set-cdr! ( obj pair-obj -- ) + drop dup + rot swap cdr-type-cells + ! + cdr-cells + ! +; + +: caar car car ; +: cadr cdr car ; +: cdar car cdr ; +: cddr cdr cdr ; + +: nil 0 nil-type ; +: nil? nil-type istype? ; + +: objvar create nil swap , , ; + +: value@ ( objvar -- val ) @ ; +: type@ ( objvar -- type ) 1+ @ ; +: value! ( newval objvar -- ) ! ; +: type! ( newtype objvar -- ) 1+ ! ; +: setobj ( newobj objvar -- ) dup rot swap 1+ ! ! ; +: fetchobj ( objvar -- obj ) dup @ swap 1+ @ ; + +: objeq? ( obj obj -- bool ) + rot = -rot = and ; + +\ ---- Pre-defined symbols ---- + +objvar symbol-table + +: (create-symbol) ( addr n -- symbol-obj ) + dup 0= if + 2drop nil + else + 2dup drop @ character-type 2swap + swap 1+ swap 1- + recurse + + cons + then +; + +: create-symbol ( -- ) + bl word + count + + (create-symbol) + drop symbol-type + + 2dup + + symbol-table fetchobj + cons + symbol-table setobj + + create swap , , + does> dup @ swap 1+ @ +; + +create-symbol quote quote-symbol +create-symbol define define-symbol +create-symbol set! set!-symbol + +\ ---- Environments ---- + +objvar global-env + +: enclosing-env ( env -- env ) + cdr ; + +: first-frame ( env -- frame ) + car ; + +: make-frame ( vars vals -- frame ) + cons ; + +: frame-vars ( frame -- vars ) + car ; + +: frame-vals ( frame -- vals ) + cdr ; + +: add-binding ( var val frame -- ) + 2swap 2over frame-vals cons + 2over set-car! + 2swap 2over frame-vars cons + swap set-cdr! +; + +: extend-env ( vars vals env -- env ) + >R >R + make-frame + R> R> + cons +; + +objvar vars +objvar vals + +: lookup-var-frame ( var frame -- val? bool ) + 2dup frame-vars vars setobj + frame-vals vals setobj + + begin + vars fetchobj nil objeq? false = + while + 2dup vars fetchobj car objeq? if + 2drop + vals fetchobj car true + exit + then + + vars fetchobj cdr vars setobj + vals fetchobj cdr vals setobj + repeat + + 2drop false +; + +: lookup-var ( var env -- val ) + begin + 2dup nil objeq? false = + while + 2over 2over first-frame + lookup-var-frame if + -rot 2drop -rot 2drop + exit + then + + enclosing-env + repeat + + 2drop + bold fg red ." Unbound variable " print ." . Aborting." reset-term cr + abort +; \ ---- Read ---- @@ -260,7 +406,7 @@ parse-idx-stack parse-idx-sp ! inc-parse-idx ; -: readstring ( -- str-obj ) +: readstring ( -- charlist ) nextchar [char] " = if inc-parse-idx @@ -292,9 +438,73 @@ parse-idx-stack parse-idx-sp ! cons ; +: readsymbol ( -- charlist ) + delim? if nil exit then + + nextchar inc-parse-idx character-type + + recurse + + cons +; + +: charlist-equiv ( charlist charlist -- bool ) + + 2over 2over + + \ One or both nil + nil? -rot 2drop + if + nil? -rot 2drop + if + 2drop 2drop true exit + else + 2drop 2drop false exit + then + else + nil? -rot 2drop + if + 2drop 2drop false exit + then + then + + 2over 2over + + \ Neither nil + car drop -rot car drop = if + cdr 2swap cdr recurse + else + 2drop 2drop false + then +; + +: charlist>symbol ( charlist -- symbol-obj ) + + symbol-table fetchobj + + begin + nil? false = + while + 2over 2over + car drop pair-type + charlist-equiv if + 2swap 2drop + car + exit + else + cdr + then + repeat + + 2drop + drop symbol-type 2dup + symbol-table fetchobj cons + symbol-table setobj +; + defer read -: readpair ( -- obj ) +: readpair ( -- pairobj ) eatspaces \ Empty lists @@ -389,33 +599,60 @@ defer read exit then + nextchar [char] ' = if + inc-parse-idx + quote-symbol recurse nil cons cons exit + then + eof? if bold fg blue ." Moriturus te saluto." reset-term ." ok" cr quit then - bold fg red ." Error parsing string starting at character '" - nextchar emit - ." '. Aborting." reset-term cr - abort + \ Anything else is assumed to be a symbol + readsymbol charlist>symbol ; is read \ ---- Eval ---- : self-evaluating? ( obj -- obj bool ) - number-type istype? if true exit then boolean-type istype? if true exit then + number-type istype? if true exit then character-type istype? if true exit then string-type istype? if true exit then nil-type istype? if true exit then - false ; -: eval - \ self-evaluating? if - \ exit - \ then - exit + false +; + +: tagged-list? ( obj tag-obj -- obj bool ) + 2over + pair-type istype? false = if + 2drop 2drop false + else + car objeq? + then ; + +: quote? ( obj -- obj bool ) + quote-symbol tagged-list? ; + +: quote-body ( quote-obj -- quote-body-obj ) + cadr ; + +: eval ( obj env -- result ) + 2swap + + self-evaluating? if + 2swap 2drop + exit + then + + quote? if + quote-body + 2swap 2drop + exit + then bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr abort @@ -462,6 +699,13 @@ defer read (printstring) [char] " emit ; +: printsymbol ( symbolobj -- ) + nil-type istype? if 2drop exit then + + 2dup car drop emit + cdr recurse +; + : printnil ( nilobj -- ) 2drop ." ()" ; @@ -480,6 +724,7 @@ defer print boolean-type istype? if printbool exit then character-type istype? if printchar exit then string-type istype? if printstring exit then + symbol-type istype? if printsymbol exit then nil-type istype? if printnil exit then pair-type istype? if ." (" printpair ." )" exit then @@ -498,7 +743,7 @@ defer print begin cr bold fg green ." > " reset-term read - eval + global-env fetchobj eval fg cyan ." ; " print reset-term again ;