X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme.4th;h=7fa85ac2e92786ad183b95721d6b3c6d3cf02a89;hb=a5871b187b34ca1eaf925658c1bc49a547593396;hp=269eb5205833ce048a8ec5c56d12914b75be6615;hpb=0ee4f0c047934f6be3877babb5cf99c8cce71e8d;p=scheme.forth.jl.git diff --git a/scheme.4th b/scheme.4th index 269eb52..7fa85ac 100644 --- a/scheme.4th +++ b/scheme.4th @@ -4,16 +4,23 @@ scheme definitions include term-colours.4th include defer-is.4th -0 constant number-type +\ ------ Types ------ + +0 constant fixnum-type 1 constant boolean-type 2 constant character-type -3 constant nil-type -4 constant pair-type -5 constant symbol-type -: istype? ( obj -- obj b ) +3 constant string-type +4 constant nil-type +5 constant pair-type +6 constant symbol-type +7 constant primitive-proc-type +8 constant compound-proc-type +: 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 @@ -45,8 +52,331 @@ 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+ ! ; +: obj! ( newobj objvar -- ) dup rot swap 1+ ! ! ; +: obj@ ( objvar -- obj ) dup @ swap 1+ @ ; + +: objeq? ( obj obj -- bool ) + rot = -rot = and ; + +: 2rot ( a1 a2 b1 b2 c1 c2 -- b1 b2 c1 c2 a1 a2 ) + >R >R ( a1 a2 b1 b2 ) + 2swap ( b1 b2 a1 a2 ) + R> R> ( b1 b2 a1 a2 c1 c2 ) + 2swap +; + +: -2rot ( a1 a2 b1 b2 c1 c2 -- c1 c2 a1 a2 b1 b2 ) + 2swap ( a1 a2 c1 c2 b1 b2 ) + >R >R ( a1 a2 c1 c2 ) + 2swap ( c1 c2 a1 a2 ) + R> R> +; + +\ }}} + +\ ---- Pre-defined symbols ---- {{{ + +objvar symbol-table + +: duplicate-charlist ( charlist -- copy ) + 2dup nil objeq? false = if + 2dup car 2swap cdr recurse cons + then ; + +: 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 obj@ + + 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 obj@ cons + symbol-table obj! +; + + +: (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 obj@ + cons + symbol-table obj! + + create swap , , + does> dup @ swap 1+ @ +; + +create-symbol quote quote-symbol +create-symbol define define-symbol +create-symbol set! set!-symbol +create-symbol ok ok-symbol +create-symbol if if-symbol +create-symbol lambda lambda-symbol +create-symbol λ λ-symbol + +\ }}} + +\ ---- Environments ---- {{{ + +: 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-cdr! + 2swap 2over frame-vars cons + 2swap set-car! +; + +: extend-env ( vars vals env -- env ) + >R >R + make-frame + R> R> + cons +; + +objvar vars +objvar vals + +: get-vars-vals-frame ( var frame -- bool ) + 2dup frame-vars vars obj! + frame-vals vals obj! + + begin + vars obj@ nil objeq? false = + while + 2dup vars obj@ car objeq? if + 2drop true + exit + then + + vars obj@ cdr vars obj! + vals obj@ cdr vals obj! + repeat + + 2drop false +; + +: get-vars-vals ( var env -- vars? vals? bool ) + + begin + 2dup nil objeq? false = + while + 2over 2over first-frame + get-vars-vals-frame if + 2drop 2drop + vars obj@ vals obj@ true + exit + then + + enclosing-env + repeat + + 2drop 2drop + false +; + +hide vars +hide vals + +: lookup-var ( var env -- val ) + get-vars-vals if + 2swap 2drop car + else + bold fg red ." Tried to read unbound variable." reset-term cr abort + then +; + +: set-var ( var val env -- ) + >R >R 2swap R> R> ( val var env ) + get-vars-vals if + 2swap 2drop ( val vals ) + set-car! + else + bold fg red ." Tried to set unbound variable." reset-term cr abort + then +; + +objvar env + +: define-var ( var val env -- ) + env obj! + + 2over env obj@ ( var val var env ) + get-vars-vals if + 2swap 2drop ( var val vals ) + set-car! + 2drop + else + env obj@ + first-frame ( var val frame ) + add-binding + then +; + +hide env + +objvar global-env +nil nil nil extend-env +global-env obj! + +\ }}} + +\ ---- Primitives ---- {{{ -\ ---- Read ---- +: make-primitive ( cfa -- ) + bl word + count + + (create-symbol) + drop symbol-type + + 2dup + + symbol-table obj@ + cons + symbol-table obj! + + rot primitive-proc-type ( var prim ) + global-env obj@ define-var +; + +: arg-count-error + bold fg red ." Incorrect argument count." reset-term cr + abort +; + +: ensure-arg-count ( args n -- ) + dup 0= if + drop nil objeq? false = if + arg-count-error + then + else + -rot 2dup nil objeq? if + arg-count-error + then + + cdr rot 1- recurse + then +; + +: arg-type-error + bold fg red ." Incorrect argument type." reset-term cr + abort +; + +: ensure-arg-type ( arg type -- arg ) + istype? false = if + arg-type-error + then +; + +include scheme-primitives.4th + +\ }}} + +\ ---- Read ---- {{{ + +defer read variable parse-idx variable stored-parse-idx @@ -110,12 +440,27 @@ parse-idx-stack parse-idx-sp ! nextchar [char] ) = or ; +: commentstart? ( -- bool ) + nextchar [char] ; = ; + : eatspaces + + false \ Indicates whether or not we're eating a comment + begin - whitespace? + dup whitespace? or commentstart? or while + dup nextchar '\n' = and if + invert \ Stop eating comment + else + dup false = commentstart? and if + invert \ Begin eating comment + then + then + inc-parse-idx repeat + drop ; : digit? ( -- bool ) @@ -126,10 +471,23 @@ parse-idx-stack parse-idx-sp ! : minus? ( -- bool ) nextchar [char] - = ; -: number? ( -- bool ) - digit? minus? or false = if - false - exit +: plus? ( -- bool ) + nextchar [char] + = ; + +: fixnum? ( -- bool ) + minus? plus? or if + inc-parse-idx + + delim? if + dec-parse-idx + false exit + else + dec-parse-idx + then + else + digit? false = if + false exit + then then push-parse-idx @@ -212,10 +570,15 @@ parse-idx-stack parse-idx-sp ! : pair? ( -- bool ) nextchar [char] ( = ; +: string? ( -- bool ) + nextchar [char] " = ; : readnum ( -- num-atom ) - minus? dup if + plus? minus? or if + minus? inc-parse-idx + else + false then 0 @@ -227,7 +590,7 @@ parse-idx-stack parse-idx-sp ! swap if negate then - number-type + fixnum-type ; : readbool ( -- bool-atom ) @@ -257,9 +620,49 @@ parse-idx-stack parse-idx-sp ! inc-parse-idx ; -defer read +: readstring ( -- charlist ) + nextchar [char] " = if + inc-parse-idx -: readpair ( -- obj ) + delim? false = if + bold fg red + ." No delimiter following right double quote. Aborting." cr + reset-term abort + then + + dec-parse-idx + + 0 nil-type exit + then + + nextchar [char] \ = if + inc-parse-idx + nextchar case + [char] n of '\n' endof + [char] " of [char] " endof + [char] \ + endcase + else + nextchar + then + inc-parse-idx character-type + + recurse + + cons +; + +: readsymbol ( -- charlist ) + delim? if nil exit then + + nextchar inc-parse-idx character-type + + recurse + + cons +; + +: readpair ( -- pairobj ) eatspaces \ Empty lists @@ -306,7 +709,7 @@ defer read eatspaces - number? if + fixnum? if readnum exit then @@ -321,6 +724,22 @@ defer read exit then + string? if + inc-parse-idx + + readstring + drop string-type + + nextchar [char] " <> if + bold red ." Missing closing double-quote." reset-term cr + abort + then + + inc-parse-idx + + exit + then + pair? if inc-parse-idx @@ -340,38 +759,278 @@ defer read exit then + nextchar [char] ' = if + inc-parse-idx + quote-symbol recurse nil cons cons exit + then + eof? if + inc-parse-idx 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 parsed as a symbol + readsymbol charlist>symbol + + \ Replace λ with lambda + 2dup λ-symbol objeq? if + 2drop lambda-symbol + then + ; is read -\ ---- Eval ---- +\ }}} + +\ ---- Eval ---- {{{ + +defer eval : self-evaluating? ( obj -- obj bool ) - number-type istype? if true exit then boolean-type istype? if true exit then + fixnum-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 ; + +: variable? ( obj -- obj bool ) + symbol-type istype? ; + +: definition? ( obj -- obj bool ) + define-symbol tagged-list? ; + +: make-lambda ( params body -- lambda-exp ) + lambda-symbol -2rot cons cons ; + +: definition-var ( obj -- var ) + cdr car + symbol-type istype? false = if car then +; + +: definition-val ( obj -- val ) + 2dup cdr car symbol-type istype? if + 2drop + cdr cdr car + else + cdr 2swap cdr cdr + make-lambda + then +; + +: assignment? ( obj -- obj bool ) + set!-symbol tagged-list? ; + +: assignment-var ( obj -- var ) + cdr car ; + +: assignment-val ( obj -- val ) + cdr cdr car ; + +: eval-definition ( obj env -- res ) + 2swap + 2over 2over ( env obj env obj ) + definition-val 2swap ( env obj valexp env ) + eval ( env obj val ) + + 2swap definition-var 2swap ( env var val ) + + 2rot ( var val env ) + define-var + + ok-symbol +; + +: eval-assignment ( obj env -- res ) + 2swap + 2over 2over ( env obj env obj ) + assignment-val 2swap ( env obj valexp env ) + eval ( env obj val ) + + 2swap assignment-var 2swap ( env var val ) + + 2rot ( var val env ) + set-var + + ok-symbol +; + +: if? ( obj -- obj bool ) + if-symbol tagged-list? ; + +: if-predicate ( ifobj -- pred ) + cdr car ; + +: if-consequent ( ifobj -- conseq ) + cdr cdr car ; + +: if-alternative ( ifobj -- alt|false ) + cdr cdr cdr + 2dup nil objeq? if + 2drop false + else + car + then ; + +: false? ( boolobj -- boolean ) + boolean-type istype? if + false boolean-type objeq? + else + 2drop false + then +; + +: true? ( boolobj -- bool ) + false? invert ; + +: lambda? ( obj -- obj bool ) + lambda-symbol tagged-list? ; + +: lambda-parameters ( obj -- params ) + cdr car ; + +: lambda-body ( obj -- body ) + cdr cdr ; + +: make-procedure ( params body env -- proc ) + nil + cons cons cons + drop compound-proc-type +; + +: application? ( obj -- obj bool) + pair-type istype? ; + +: operator ( obj -- operator ) + car ; + +: operands ( obj -- operands ) + cdr ; + +: nooperands? ( operands -- bool ) + nil objeq? ; + +: first-operand ( operands -- operand ) + car ; + +: rest-operands ( operands -- other-operands ) + cdr ; + +: list-of-vals ( args env -- vals ) + 2swap + + 2dup nooperands? if + 2swap 2drop + else + 2over 2over first-operand 2swap eval + -2rot rest-operands 2swap recurse + cons + then +; + +: apply ( proc args ) + 2swap dup case + primitive-proc-type of + drop execute + endof + + compound-proc-type of + 2drop 2drop + ." Compound procedures not yet implemented." cr + ok-symbol + endof + + bold fg red ." Object not applicable. Aboring." reset-term cr + abort + endcase +; + +:noname ( obj env -- result ) + 2swap + + self-evaluating? if + 2swap 2drop + exit + then + + quote? if + quote-body + 2swap 2drop + exit + then + + variable? if + 2swap lookup-var + exit + then + + definition? if + 2swap eval-definition + exit + then + + assignment? if + 2swap eval-assignment + exit + then + + if? if + 2over 2over + if-predicate + 2swap eval + + true? if + if-consequent + else + if-alternative + then + + 2swap ['] eval goto + then + + lambda? if + 2dup lambda-parameters + 2swap lambda-body + 2rot make-procedure + exit + then + + application? if + 2over 2over + operator 2swap eval + -2rot + operands 2swap list-of-vals + + apply + exit + then bold fg red ." Error evaluating expression - unrecognized type. Aborting." reset-term cr abort -; +; is eval + +\ }}} -\ ---- Print ---- +\ ---- Print ---- {{{ + +defer print : printnum ( numobj -- ) drop 0 .R ; @@ -394,10 +1053,34 @@ defer read endcase ; +: (printstring) ( stringobj -- ) + nil-type istype? if 2drop exit then + + 2dup car drop dup + case + '\n' of ." \n" drop endof + [char] \ of ." \\" drop endof + [char] " of [char] \ emit [char] " emit drop endof + emit + endcase + + cdr recurse +; +: printstring ( stringobj -- ) + [char] " emit + (printstring) + [char] " emit ; + +: printsymbol ( symbolobj -- ) + nil-type istype? if 2drop exit then + + 2dup car drop emit + cdr recurse +; + : printnil ( nilobj -- ) 2drop ." ()" ; -defer print : printpair ( pairobj -- ) 2dup car print @@ -407,17 +1090,29 @@ defer print ." . " print ; +: printprim ( primobj -- ) + 2drop ." " ; + +: printcomp ( primobj -- ) + 2drop ." " ; + :noname ( obj -- ) - number-type istype? if printnum exit then + fixnum-type istype? if printnum exit then 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 + primitive-proc-type istype? if printprim exit then + compound-proc-type istype? if printcomp exit then bold fg red ." Error printing expression - unrecognized type. Aborting" reset-term cr abort ; is print +\ }}} + \ ---- REPL ---- : repl @@ -429,9 +1124,11 @@ defer print begin cr bold fg green ." > " reset-term read - eval + global-env obj@ eval fg cyan ." ; " print reset-term again ; forth definitions + +\ vim:fdm=marker