commit e52009c0a2dd4735a08834f70d5b28392e3eddd5 Author: Peter McGoron Date: Fri Oct 18 12:43:01 2024 -0400 cond-values: add with example diff --git a/COPYING b/COPYING new file mode 100644 index 0000000..d645695 --- /dev/null +++ b/COPYING @@ -0,0 +1,202 @@ + + Apache License + Version 2.0, January 2004 + http://www.apache.org/licenses/ + + TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION + + 1. Definitions. + + "License" shall mean the terms and conditions for use, reproduction, + and distribution as defined by Sections 1 through 9 of this document. + + "Licensor" shall mean the copyright owner or entity authorized by + the copyright owner that is granting the License. + + "Legal Entity" shall mean the union of the acting entity and all + other entities that control, are controlled by, or are under common + control with that entity. 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We also recommend that a + file or class name and description of purpose be included on the + same "printed page" as the copyright notice for easier + identification within third-party archives. + + Copyright [yyyy] [name of copyright owner] + + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. diff --git a/cond-values.scm b/cond-values.scm new file mode 100644 index 0000000..099536c --- /dev/null +++ b/cond-values.scm @@ -0,0 +1,187 @@ +;;; Copyright 2024 Peter McGoron +;;; Licensed under the Apache License, Version 2.0 (the "License"); +;;; you may not use this file except in compliance with the License. +;;; You may obtain a copy of the License at +;;; +;;; http://www.apache.org/licenses/LICENSE-2.0 +;;; +;;; Unless required by applicable law or agreed to in writing, software +;;; distributed under the License is distributed on an "AS IS" BASIS, +;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or +;;; implied. See the License for the specific language governing +;;; permissions and limitations under the License. + +(import srfi-1) + +;;; AFTER executes a body after multiple tests. +;;; +;;; The form of the syntax is +;;; (AFTER (BINDING ...) BODY ...) +;;; +;;; where BODY ... is a Scheme body. Each BINDING is evaluated in order, +;;; where BINDING is +;;; +;;; (VALUE => FORMAL): FORMAL is a LAMBDA formal and VALUE is a something +;;; that returns multiple values. If VALUE evaluates to no values, the +;;; test fails and the entire AFTER form returns no values. +;;; +;;; (WHEN TEST): Evaluates TEST. If TEST is #F then the entire AFTER form +;;; returns no values. +;;; +;;; If all BINDINGs pass, then BODY is executed and its return value is +;;; the return of AFTER. +(define-syntax after + (syntax-rules (when let =>) + ((after ((let value => formal) conditionals ...) body ...) + (call-with-values (lambda () value) + (lambda returned + (if (null? returned) + (values) + (apply (lambda formal (after (conditionals ...) body ...)) + returned))))) + ((after ((let formal value ...) conditionals ...) body ...) + (after ((let (begin value ...) => formal) conditionals ...) + body ...)) + ((after ((when boolean) conditionals ...) body ...) + (if boolean + (after (conditionals ...) body ...) + (values))) + ((after () body ...) + (begin body ...)))) + +(define-syntax apply-after + (syntax-rules () + ((apply-after value receiver) + (after ((let value => formal)) + (apply receiver formal))))) + +;;; (COND-VALUES CLAUSE ...) is like COND, but it tests for empty VALUES +;;; instead of #F. +;;; +;;; Each CLAUSE is: +;;; +;;; (BODY ...): Executes BODY. If BODY returns no values, then try the +;;; rest of the clauses. If BODY returns values, those values are the +;;; return values of COND-VALUES. +;;; (ELSE BODY ...): Must occur at the end. Executes BODY and returns +;;; whatever BODY returns. +;;; +;;; If there is no ELSE clause and all CLAUSEs fail, COND-VALUES returns +;;; no values. +(define-syntax cond-values + (syntax-rules (else) + ((cond-values (else body ...)) + (begin body ...)) + ((cond-values value rest ...) + (call-with-values (lambda () value) + (lambda returned + (if (null? returned) + (cond-values rest ...) + (apply values returned))))) + ((cond-values) (values)))) + +;;; (DEFINE-RECORD-TYPE/DESTRUCTOR TYPENAME +;;; (CSTR FIELDS ...) +;;; PREDICATE? +;;; DESTRUCTOR +;;; (FIELD GETTER SETTER ...) +;;; ...) +;;; +;;; creates an SRFI-9/R7RS record type. The syntax is the same, except +;;; that after the PREDICATE field and before the getter/setter fields +;;; is an identifier, DESTRUCTOR. +;;; +;;; This macro defines a procedure (DESTRUCTOR RECORD) that returns each +;;; field of RECORD as values, or no values if RECORD is not a TYPENAME +;;; record. +(define-syntax define-record-type/destructor + (syntax-rules () + ((define-record-type/destructor typename + (cstr fields ...) + predicate? + destructor + (field getter setter ...) + ...) + (begin + (define-record-type typename + (cstr fields ...) + predicate? + (field getter setter ...) + ...) + (define (destructor record) + (after ((when (predicate? record))) + (values (getter record) ...))))))) + +;;; ;;;;;;;;;;;;; +;;; Helper functions +;;; ;;;;;;;;;;;;; + +;;; Returns the CAR and CDR of X as values when X is a pair, and no values +;;; otherwise. +(define (pair-d x) + (after ((when (pair? x))) + (values (car x) (cdr x)))) + +(define (assq-d val alist) + (let ((pair (assq val alist))) + (after ((when (pair? pair))) + (cdr pair)))) + +;;; Returns the list as values when WHOLE-LIST has length NUM, and no +;;; values otherwise. +(define (length* whole-list num) + (when (<= num 0) + (error "invalid number" 'length* whole-list num)) + + (let length* ((lst whole-list) + (num num)) + (cond-values + (after ((when (null? lst)) + (when (= num 0))) + (apply values whole-list)) + (after ((when (pair? lst)) + (when (> num 0))) + (length* (cdr lst) (- num 1)))))) + +;;; Returns the list as values when WHOLE-LIST has at least length NUM, +;;; and no values otherwise. +(define (length-at-least whole-list num) + (when (<= num 0) + (error "invalid number" 'length-at-least whole-list num)) + + (let length-at-least ((lst whole-list) + (num num)) + (cond-values + (after ((when (= num 0)) + (when (or (null? lst) + (pair? lst)))) + (apply values whole-list)) + (after ((when (> num 0)) + (when (pair? lst))) + (length-at-least (cdr lst) (- num 1)))))) + +;;; Helper function. +(define (null-cdr? lst) (null? (cdr lst))) + +;;; MAP-VALUES returns (VALUES L1 L2 ...), where L1 is the first +;;; value returned from (F (CAR LST)), (F (CADR LST)), ... and so on. +(define (map-values f . lists) + (define (null-cdr? lst) (null? (cdr lst))) + (let-values ((new-values (apply f (map car lists)))) + (if (any null-cdr? lists) + (apply values (map list new-values)) + (let-values ((returned (apply map-values f (map cdr lists)))) + (apply values (map cons new-values returned)))))) + +;;; (ANY-VALUES F (A1 A2 ...) (B1 B2 ...) ...) runs +;;; (F A1 B1 ...) and checks if there any returned values. If there are +;;; none, runs (F A2 B2 ...), and so on. +;;; +;;; If any of the lists end, then ANY-VALUES returns no values. +(define (any-values f . lists) + (after ((when (not (null? lists))) + (when (all pair? lists))) + (let-values ((returned (apply f (map car lists)))) + (if (null? returned) + (apply any-values f (map cdr lists)) + (apply values returned))))) diff --git a/units.scm b/units.scm new file mode 100644 index 0000000..08694a9 --- /dev/null +++ b/units.scm @@ -0,0 +1,167 @@ +;;; Copyright 2024 Peter McGoron +;;; Licensed under the Apache License, Version 2.0 (the "License"); +;;; you may not use this file except in compliance with the License. +;;; You may obtain a copy of the License at +;;; +;;; http://www.apache.org/licenses/LICENSE-2.0 +;;; +;;; Unless required by applicable law or agreed to in writing, software +;;; distributed under the License is distributed on an "AS IS" BASIS, +;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or +;;; implied. See the License for the specific language governing +;;; permissions and limitations under the License. +;;; +;;; Example of COND-VALUES using units. + +(load "cond-values.scm") + +(define *si-prefixes* + '((quetta . #e1e30) + (ronna . #e1e27) + (yotta . #e1e24) + (zetta . #e1e21) + (exa . #e1e18) + (peta . #e1e15) + (tera . #e1e12) + (giga . #e1e9) + (mega . #e1e6) + (kilo . #e1e3) + (hecto . #e1e2) + (deka . #e1e1) + (deci . #e1e-1) + (centi . #e1e-2) + (milli . #e1e-3) + (micro . #e1e-6) + (nano . #e1e-9) + (pico . #e1e-12) + (femto . #e1e-15) + (atto . #e1e-18) + (zepto . #e1e-21) + (yocto . #e1e-24) + (ronto . #e1e-27) + (quecto . #e1e-30))) + +(define *si-algebra* + `((/ . ,/) + (* . ,*))) + +(define (atom-d unit) + (after ((when (or (symbol? unit) + (and (number? unit) (exact? unit))))) + unit)) + +(define (prefixed-d unit) + (after ((let (length* unit 2) => (head unit)) + (let (assq-d head *si-prefixes*) => (factor))) + (values factor unit))) + +(define (power-d unit) + (after ((let (length* unit 3) => (head number unit)) + (when (eq? head '^))) + (values number unit))) + +(define (algebra-function-d unit) + (after ((let (length-at-least unit 3) => (head . rest)) + (let (assq-d head *si-algebra*) => (procedure))) + (values head procedure rest))) + +(define (remove-prefixes unit) + (cond-values + (after ((let (atom-d unit) => (unit))) + (values 1 unit)) + ;; + (after ((let (prefixed-d unit) => (factor unit))) + (let-values (((sub-factor unit-w/o-factors) + (remove-prefixes unit))) + (values (* sub-factor factor) unit-w/o-factors))) + ;; + (after ((let (power-d unit) => (power unit))) + (let-values (((sub-factor sub-unit) + (remove-prefixes unit))) + (values (expt sub-factor power) + (list '^ power sub-unit)))) + ;; + (after ((let (algebra-function-d unit) => (head proc units))) + (let-values (((factors units) + (map-values remove-prefixes units))) + (values (apply proc factors) + (cons head units)))) + (else (error "invalid unit" unit)))) + +(remove-prefixes '(/ (* (centi meter) (centi meter)) + volt + second)) +(remove-prefixes '(/ (^ 2 (centi meter)) + volt + second)) + +(define (make-unit-destructor atom prefixed power algebra-function on-else) + (lambda (unit) + (cond-values + (apply-after (atom-d unit) atom) + (apply-after (prefixed-d unit) prefixed) + (apply-after (power-d unit) power) + (apply-after (algebra-function-d unit) algebra-function) + (else (on-else unit))))) + +(import r7rs) + +(define (remove-prefixes unit) + (define (on-atom unit) + (values 1 unit)) + (define (on-prefixed prefix-factor unit) + (let-values (((sub-prefix sub-unit) (remove-prefixes unit))) + (values (* prefix-factor sub-prefix) sub-unit))) + (define (on-power power unit) + (let-values (((sub-prefix sub-unit) (remove-prefixes unit))) + (values (expt sub-prefix power) sub-unit))) + (define (on-algebra-function symbol procedure units) + (let-values (((prefixes units) (map-values remove-prefixes units))) + (values (apply procedure prefixes) + (cons symbol units)))) + (define (on-else unit) + (error "invalid unit" 'remove-prefixes unit)) + (define remove-prefixes + (make-unit-destructor on-atom + on-prefixed + on-power + on-algebra-function)) + (remove-prefixes unit)) + +(define remove-prefixes-destructors '()) +(define remove-prefixes-handlers '()) + +(define (add-remove-prefixes-handler destructor handler) + (set! remove-prefixes-destructors + (cons destructor remove-prefixes-destructors)) + (set! remove-prefixes-handlers + (cons handler remove-prefixes-handlers))) + +(define (remove-prefixes unit) + (cond-values + (any-values (lambda (destructor handler) + (apply-after (destructor unit) handler)) + remove-prefixes-destructors + remove-prefixes-handlers) + (else (error "invalid unit" unit)))) + +(add-remove-prefixes-handler atom-d (lambda (unit) + (values 1 unit))) + +(remove-prefixes 'gram) +(remove-prefixes '(kilo gram)) + +(add-remove-prefixes-handler prefixed-d + (lambda (factor unit) + (let-values (((sub-factor sub-unit) + (remove-prefixes unit))) + (values (* factor sub-factor) sub-unit)))) + +(add-remove-prefixes-handler + algebra-function-d + (lambda (head procedure units) + (let-values (((factors units) (map-values remove-prefixes units))) + (values (apply procedure factors) + (cons head units))))) + +(remove-prefixes '(/ (kilo meter) (micro second))) diff --git a/units.sml b/units.sml new file mode 100644 index 0000000..0a821c1 --- /dev/null +++ b/units.sml @@ -0,0 +1,66 @@ +datatype si_prefix += QUETTA | RONNA | YOTTA | ZETTA | EXA | PETA | TERA | GIGA | MEGA +| KILO | HECTO | DEKA | DECI | CENTI | MILLI | MICRO | NANO +| PICO | FEMTO | ATTO | ZEPTO | YOCTO | RONTO | QUECTO; + +datatype si_function += DIVISION | MULT; + +datatype si_unit += UNIT of string +| PREFIX of si_prefix * si_unit +| ALGEBRA of si_function * si_unit list +; + +fun factor_of_prefix QUETTA = 1e30 + | factor_of_prefix RONNA = 1e27 + | factor_of_prefix YOTTA = 1e24 + | factor_of_prefix ZETTA = 1e21 + | factor_of_prefix EXA = 1e18 + | factor_of_prefix PETA = 1e15 + | factor_of_prefix TERA = 1e12 + | factor_of_prefix GIGA = 1e9 + | factor_of_prefix MEGA = 1e6 + | factor_of_prefix KILO = 1e3 + | factor_of_prefix HECTO = 1e2 + | factor_of_prefix DEKA = 1e1 + | factor_of_prefix DECI = 1e~1 + | factor_of_prefix CENTI = 1e~2 + | factor_of_prefix MILLI = 1e~3 + | factor_of_prefix MICRO = 1e~6 + | factor_of_prefix NANO = 1e~9 + | factor_of_prefix PICO = 1e~12 + | factor_of_prefix FEMTO = 1e~15 + | factor_of_prefix ATTO = 1e~18 + | factor_of_prefix ZEPTO = 1e~21 + | factor_of_prefix YOCTO = 1e~24 + | factor_of_prefix RONTO = 1e~27 + | factor_of_prefix QUECTO = 1e~30 + ; + +fun apply_function DIVISION (head::[]) = head + | apply_function DIVISION [] = raise Match + | apply_function DIVISION (x::y::rest) + = apply_function DIVISION (x/y::rest) + | apply_function MULT [] = 1.0 + | apply_function MULT (head::[]) = head + | apply_function MULT (x::y::rest) + = apply_function MULT (x*y::rest) + ; + +fun car (x,y) = x; +fun cdr (x,y) = y; + +fun remove_prefixes (UNIT x) = (1e0, UNIT x) + | remove_prefixes (PREFIX (prefix, the_unit)) + = let val (factor, sub_unit) = remove_prefixes the_unit + in (factor * (factor_of_prefix prefix), sub_unit) + end + | remove_prefixes (ALGEBRA (function, units)) + = let val returned = map remove_prefixes units; + val factors = map car returned; + val units = map cdr returned; + in + (apply_function function factors, (ALGEBRA (function, units))) + end + ;