261 lines
9.4 KiB
Racket
261 lines
9.4 KiB
Racket
#lang racket
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;;; dds/utils
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;;; Various utilities.
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(require
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graph
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(for-syntax syntax/parse racket/list))
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(provide
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;; Functions
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(contract-out [eval-with (-> variable-mapping? any/c any)]
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[extract-symbols (-> any/c list?)]
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[any->string (-> any/c string?)]
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[stringify-variable-mapping (-> variable-mapping? string-variable-mapping?)]
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[string->any (-> string? any/c)]
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[read-org-table (-> string? (listof any/c))]
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[unstringify-pairs (-> (listof (general-pair/c string? any/c))
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(listof (general-pair/c symbol? any/c)))]
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[read-org-variable-mapping (-> string? variable-mapping?)]
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[update-vertices/unweighted (-> graph? (-> any/c any/c) graph?)]
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[update-graph (->* (graph?)
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(#:v-func (-> any/c any/c)
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#:e-func (-> any/c any/c))
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graph?)]
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[pretty-print-set (-> generic-set? string?)])
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;; Contracts
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(contract-out [variable-mapping? contract?]
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[string-variable-mapping? contract?]
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[general-pair/c (-> contract? contract? contract?)])
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;; Syntax
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auto-hash-ref/explicit auto-hash-ref/: sgfy unorg dotit)
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;;; ===================
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;;; HashTable Injection
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;;; ===================
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;;; This section of the file contains some utilities to streamline the
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;;; usage of hash tables mapping symbols to values. The goal is
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;;; essentially to avoid having to write explicit hash-ref calls.
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;;; A variable mapping is a hash table mapping symbols to values.
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(define (variable-mapping? dict) (hash/c symbol? any/c))
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;;; Given a (HashTable Symbol a) and a sequence of symbols, binds
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;;; these symbols to the values they are associated to in the hash
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;;; table, then puts the body in the context of these bindings.
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;;;
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;;; > (let ([ht #hash((a . 1) (b . 2))])
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;;; (auto-hash-ref/explicit (ht a b) (+ a (* 2 b))))
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;;; 5
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;;;
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;;; Note that only one expression can be supplied in the body.
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(define-syntax (auto-hash-ref/explicit stx)
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(syntax-parse stx
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[(_ (ht:id xs:id ...) body:expr)
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#`(let #,(for/list ([x (syntax->list #'(xs ...))])
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#`[#,x (hash-ref ht '#,x)])
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body)]))
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;;; Given an expression and a (HashTable Symbol a), looks up the
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;;; symbols with a leading semicolon and binds them to the value they
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;;; are associated to in the hash table.
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;;;
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;;; > (let ([ht #hash((a . 1) (b . 2))])
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;;; (auto-hash-ref/: ht (+ :a (* 2 :b))))
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;;; 5
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;;;
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;;; Note that the symbol :a is matched to the key 'a in the hash
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;;; table.
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;;;
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;;; Note that only one expression can be supplied in the body.
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(define-syntax (auto-hash-ref/: stx)
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(syntax-parse stx
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[(_ ht:id body)
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(let* ([names/: (collect-colons (syntax->datum #'body))])
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#`(let #,(for/list ([x names/:])
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;; put x in the same context as body
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#`[#,(datum->syntax #'body x)
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(hash-ref ht '#,(strip-colon x))])
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body))]))
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;;; The helper functions for auto-hash-ref/:.
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(begin-for-syntax
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;; Collect all the symbols starting with a colon in datum.
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(define (collect-colons datum)
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(remove-duplicates
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(flatten
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(for/list ([token datum])
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(cond
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[(symbol? token)
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(let ([name (symbol->string token)])
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(if (eq? #\: (string-ref name 0))
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token
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'()))]
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[(list? token)
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(collect-colons token)]
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[else '()])))))
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;; Strip the leading colon off x.
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(define (strip-colon x)
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(let ([x-str (symbol->string x)])
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(if (eq? #\: (string-ref x-str 0))
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(string->symbol (substring x-str 1))
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x))))
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;;; Temporarily injects the mappings from the given hash table as
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;;; bindings in a namespace including racket/base and then evaluates
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;;; the expression.
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;;;
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;;; > (let ([ht #hash((a . 1) (b . 1))])
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;;; (eval-with ht '(+ b a 1)))
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;;; 3
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;;;
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;;; The local bindings from the current lexical scope are not
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;;; conserved. Therefore, the following outputs an error about a
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;;; missing identifier:
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;;;
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;;; > (let ([ht #hash((a . 1) (b . 1))]
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;;; [z 1])
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;;; (eval-with ht '(+ b z a 1)))
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;;;
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(define (eval-with ht expr)
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(parameterize ([current-namespace (make-base-namespace)])
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(for ([(x val) ht]) (namespace-set-variable-value! x val))
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(eval expr)))
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;;; Same as eval-with, but returns only the first value produced by
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;;; the evaluated expression.
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(define (eval-with1 ht expr)
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(let ([vals (call-with-values (λ () (eval-with ht expr))
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(λ vals vals))])
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(car vals)))
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;;; ==============================
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;;; Analysis of quoted expressions
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;;; ==============================
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;;; Produces a list of symbols appearing in the quoted expression
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;;; passed in the first argument.
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(define (extract-symbols form)
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(match form
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[(? symbol?) (list form)]
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[(? list?) (flatten (for/list ([x form])
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(extract-symbols x)))]
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[else '()]))
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;;; =========================
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;;; Interaction with Org-mode
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;;; =========================
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;;; Org-mode supports laying out the output of code blocks as tables,
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;;; which is very practical for various variable mappings (e.g.,
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;;; states). However, when the hash table maps variables to lists,
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;;; Org-mode will create a column per list element, which may or may
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;;; not be the desired effect. In this section I define some
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;;; utilities for nicer interoperation with Org-mode tables. I also
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;;; define some shortcuts to reduce the number of words to type when
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;;; using dds with Org-mode. See example.org for examples of usage.
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;;; Converts any value to string.
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(define (any->string x)
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(with-output-to-string (λ () (display x))))
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;;; A string variable mapping is a mapping from variables to strings.
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(define (string-variable-mapping? dict) (hash/c symbol? string?))
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;;; Converts all the values of a variable mapping to string.
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(define (stringify-variable-mapping ht)
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(for/hash ([(key val) ht]) (values key (any->string val))))
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;;; A shortcut for variable-mapping-stingify.
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(define-syntax-rule (sgfy ht) (stringify-variable-mapping ht))
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;;; Reads any value from string.
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(define (string->any str)
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(with-input-from-string str (λ () (read))))
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;;; Reads a table from a string produced by Org-mode for a named
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;;; table. See example.org for examples.
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(define (read-org-table str) (string->any str))
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;;; A contract allowing pairs constructed via cons or via list.
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(define (general-pair/c key-contract val-contract)
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(or/c (list/c key-contract val-contract)
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(cons/c key-contract val-contract)))
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;;; Given a list of pairs of strings and some other values (possibly
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;;; strings), converts the first element of each pair to a string, and
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;;; reads the second element with string->any or keeps it as is if it
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;;; is not a string.
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(define (unstringify-pairs pairs)
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(for/list ([p pairs])
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(match p
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[(list key val)
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(cons (string->symbol key) (if (string? val)
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(string->any val)
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val))]
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[(cons key val) ; also handle improper pairs
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(cons (string->symbol key) (if (string? val)
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(string->any val)
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val))])))
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;;; Reads a variable mapping from a string, such as the one which
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;;; Org-mode produces from tables.
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(define (read-org-variable-mapping str)
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(make-hash (unstringify-pairs (read-org-table str))))
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;;; A synonym for read-org-variable-mapping.
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(define-syntax-rule (unorg str) (read-org-variable-mapping str))
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;;; Typeset the graph via graphviz and display it.
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(define-syntax-rule (dotit gr) (display (graphviz gr)))
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;;; ==========================
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;;; Additional graph utilities
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;;; ==========================
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;;; Apply a transformation to every vertex in the unweighted graph,
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;;; return the new graph. If the transformation function maps two
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;;; vertices to the same values, these vertices will be merged in the
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;;; resulting graph. The transformation function may be called
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;;; multiple times for the same vertex.
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;;;
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;;; This function does not rely on rename-vertex!, so it can be used
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;;; to permute vertex labels.
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(define (update-vertices/unweighted gr func)
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(unweighted-graph/directed
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(for/list ([e (in-edges gr)])
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(match-let ([(list u v) e])
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(list (func u) (func v))))))
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;;; Given a graph, apply a transformation v-func to every vertex label
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;;; and, if the graph is a weighted graph, the transformation e-func
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;;; to every edge label. Both transformations default to identity
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;;; functions. If gr is an weighted graph, the result is a weighted
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;;; graph. If gr is an unweighted graph, the result is an unweighted
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;;; graph.
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(define (update-graph gr #:v-func [v-func identity] #:e-func [e-func identity])
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(let ([edges (for/list ([e (in-edges gr)])
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(match-let ([(list u v) e])
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(if (unweighted-graph? gr)
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(list (v-func u) (v-func v))
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(list (e-func (edge-weight gr u v))
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(v-func u) (v-func v)))))])
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(if (unweighted-graph? gr)
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(unweighted-graph/directed edges)
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(weighted-graph/directed edges))))
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;;; ===============
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;;; Pretty printing
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;;; ===============
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;;; Pretty print a set by listing its elements in alphabetic order.
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(define (pretty-print-set s)
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(string-join (sort (set-map s any->string) string<?)))
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