p-lang thread: (now (have you (problems two)))

The Something Awful Forums > Discussion > Serious Hardware/Software Crap > YOSPOS > p-lang thread: (now (have you (problems two)))

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vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

MononcQc posted:

if your programming language doesn't have pattern matching it's a dumb language from the past.

Why wouldn't it just be a library

# ? Aug 5, 2012 18:48

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# ? Jun 11, 2024 16:16

Cocoa Crispies: Jul 20, 2001; Vehicular Manslaughter!; Pillbug

Zizzyx posted:

why doesn't that also print butts idgi

it matches the first one, so you can have a catchall farther down that only gets called when nothing above it matches

# ? Aug 5, 2012 18:57

MononcQc: May 29, 2007

Cocoa Crispies posted:

if you can't build it yourself lol

code:

    p = Matcher.new
    p.match(:alpha, wc) do
      puts "farts"
    end
    p.match(wc, :bravo) do
      puts "butts"
    end
    p[:alpha, :bravo] #=> "farts"

as long as you can pattern match on other data types that can be decent.

vapid cutlery posted:

Why wouldn't it just be a library

It can be. The important thing is that everyone should be using it in that community.

# ? Aug 5, 2012 19:20

Opinion Haver: Apr 9, 2007

MononcQc posted:

if your programming language doesn't have pattern matching it's a dumb language from the past.

# ? Aug 5, 2012 19:22

Cocoa Crispies: Jul 20, 2001; Vehicular Manslaughter!; Pillbug

MononcQc posted:

as long as you can pattern match on other data types that can be decent.

yeah that uses the "===" in ruby which does a fuzzy comparison

Ruby code:

/abc/ === "abc"
# => true
/abc/ === "abcde"
# => true
String === "abcde"
# => true
"abc" === "abcde"
# => false
5 === 6
# => false
6 === false
# => false
Fixnum === 6
# => true
Integer === 6
# => true
Integer === 6.5
# => false
Numeric === 6.5
# => true

for a Regexp it matches, for a Class it checks ancestry, by default it uses ==

i just realized i could override Wildcard#=== instead of special casing it, hello revisiting throw-away toy project from three years ago

# ? Aug 5, 2012 19:29

MononcQc: May 29, 2007

Cocoa Crispies posted:

yeah that uses the "===" in ruby which does a fuzzy comparison
Ruby code:
/abc/ === "abc"
# => true
/abc/ === "abcde"
# => true
String === "abcde"
# => true
"abc" === "abcde"
# => false
5 === 6
# => false
6 === false
# => false
Fixnum === 6
# => true
Integer === 6
# => true
Integer === 6.5
# => false
Numeric === 6.5
# => true
for a Regexp it matches, for a Class it checks ancestry, by default it uses ==

i just realized i could override Wildcard#=== instead of special casing it, hello revisiting throw-away toy project from three years ago

This does sound more like dynamic dispatch (CLOS-like) than pattern matching. You have to add something a bit like clojure's destructuring bind to it. Here's in Racket how you could pattern match on a list:

code:

> (match '(1 2 3)
    [(list 1 a ...) a])

'(2 3)

In Erlang, it would be based on something like [1, A | _] to bind A to the 2nd item in the list.

Racket has it powerful as hell -- you can expand it to use arbitrary data structures or even regexes:

code:

> (match "apple"
    [(regexp #rx"p+(.)" (list _ "l")) 'yes]
    [_ 'no])

'yes

Compared to just matching on a regex on true/false, it checks if the regex succeeds and then can extract data from the result and keep going from there. In that case, it looks whether the match ends with an "l".

Pattern matching goes one step further than just destructuring binds or dynamic dispatch.

# ? Aug 5, 2012 19:44

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

MononcQc posted:

The important thing is that everyone should be using it in that community.

for what?

# ? Aug 5, 2012 19:45

MononcQc: May 29, 2007

vapid cutlery posted:

for what?

condition branching/control flow and a large part of assignment in that language.

# ? Aug 5, 2012 19:46

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

MononcQc posted:

condition branching/control flow and a large part of assignment in that language.

i'm not really convinced

# ? Aug 5, 2012 19:48

Zombywuf: Mar 29, 2008

You really need pattern matching and unification.

Also backtracking.

# ? Aug 5, 2012 20:19

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

oh cool the "everyone should use hard computer science to write their applications" crew is out in force. cya

# ? Aug 5, 2012 20:20

Sneaking Mission: Nov 11, 2008

i recommend some duck typing in your next program. make sure its duck typed. you gotta do it

# ? Aug 5, 2012 20:24

Rufus Ping: Dec 27, 2006; I'm a Friend of Rodney Nano

duck typing is wack

# ? Aug 5, 2012 20:29

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

mo�! duck typing is mo�!

# ? Aug 5, 2012 20:29

Jonnty: Aug 2, 2007; The enemy has become a flaming star!

my programs are swan typed in the sense that users often break their arms while using them

# ? Aug 5, 2012 20:31

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

lmao php doesn't have a library function for building paths

# ? Aug 5, 2012 20:51

Sneaking Mission: Nov 11, 2008

have you tried: autovivification?

# ? Aug 5, 2012 20:54

Jonnty: Aug 2, 2007; The enemy has become a flaming star!

vapid cutlery posted:

lmao php doesn't have a library function for building paths

you mean it doesn't have a concatenation operator?? wtf

# ? Aug 5, 2012 20:59

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

Jonnty posted:

you mean it doesn't have a concatenation operator?? wtf

that isn't all there is to a function like that

# ? Aug 5, 2012 21:00

Jonnty: Aug 2, 2007; The enemy has become a flaming star!

vapid cutlery posted:

that isn't all there is to a function like that

i get super upset at double slashes in my paths too

# ? Aug 5, 2012 21:01

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

Jonnty posted:

i get super upset at double slashes in my paths too

typical PHP developer settling for mediocrity and rewriting the same thing a hundred times i guess

# ? Aug 5, 2012 21:06

Cocoa Crispies: Jul 20, 2001; Vehicular Manslaughter!; Pillbug

vapid cutlery posted:

oh cool the "everyone should use hard computer science to write their applications" crew is out in force. cya

lol

basically think of how you open a file in c

C code:

FILE* file_of_dicks = fopen("dicks.txt","r");
process_dicks(file_of_dicks);
fclose(file_of_dicks);

"tere's no error checking retard"

C code:

void process_dicks(NULL) {
  /* bitch about failure */
}

void process_dicks(FILE* file_of_dicks) {
  �
}

now there is, by having the first version that only takes null do it, and the second version only gets a file handle

if that's a "hard computer science" thing maybe you should look into php/jquery

# ? Aug 5, 2012 21:12

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

Cocoa Crispies posted:

lol

basically think of how you open a file in c
C code:
FILE* file_of_dicks = fopen("dicks.txt","r");
process_dicks(file_of_dicks);
fclose(file_of_dicks);
"tere's no error checking retard"
C code:
void process_dicks(NULL) {
  /* bitch about failure */
}

void process_dicks(FILE* file_of_dicks) {
  �
}
now there is, by having the first version that only takes null do it, and the second version only gets a file handle

if that's a "hard computer science" thing maybe you should look into php/jquery

that's a nice trivial example that can actually be written in C in fewer, easier to understand lines than what you posted

# ? Aug 5, 2012 21:15

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

i'm looking through the php api docs and apparently everyone has their own way of parsing and gluing together URL's from individual components. that's pretty loving hilarious for a language that lives on web servers

# ? Aug 5, 2012 21:18

MononcQc: May 29, 2007

vapid cutlery posted:

oh cool the "everyone should use hard computer science to write their applications" crew is out in force. cya

It's actually simpler using it. The example below creates a little hash with 3 users as keys, and the value for each is a list of their password and a secret to return whenever the password is right.

Here's the hash definition:

code:

(define users (make-hash (list (cons "tef" (list "password" "I Love Ruby"))
                               (cons "mononcqc" (list "hunter2" "I expect *******"))
                               (cons "vapid cutlery" (list "mylittlebrony" "IDGI")))))

The normal way to do things is then to:

Fetch the user from the hash
if it's there, extract the password and the secret from the value returned
if the password is the good one, return the secret, otherwise return 'false'

this is how it's done in racket:

code:

(define (login1 user pass)
  (let ([data (hash-ref users user 'undefined)]) ; fetch the entry
    (if (eq? 'undefined data)                    ; check if it's there
        #f
        (let ([passwd (car data)]                ; extract the password
              [secret (cadr data)])              ; extract the secret
          (if (eq? passwd pass)                  ; check if the password is right
              secret                             ; return the secret
              #f)))))

Using pattern matching, I can fetch from the hash, extract the values and compare them all at once

Here's the same function implemented using pattern matching:

code:

(define (login2 user pass)
  (match (hash-ref users user 'undefined)        ; fetch the value
    [(list (== pass) secret) secret]             ; deconstruct, compare & return
    [_ #f]))                                     ; not found

It's not hard to use, just somewhat harder to implement if you're writing the language or library. Having pattern matching makes code much shorter and simpler at once.

E: usage

code:

> (login1 "bad user" "nknlk")
#f
> (login1 "tef" "password")
"I Love Ruby"
> (login1 "mononcqc" "heh")
#f
> (login2 "bad user" "kjdsf")
#f
> (login2 "tef" "password")
"I Love Ruby"
> (login2 "bad user" "kjdsf")
#f

MononcQc fucked around with this message at 21:22 on Aug 5, 2012

# ? Aug 5, 2012 21:20

Zizzyx: Sep 18, 2007; INTERGALACTIC CAN CHAMPION

vapid cutlery posted:

i'm looking through the php api docs and apparently everyone has their own way of parsing and gluing together URL's from individual components. that's pretty loving hilarious for a language that lives on web servers

this is desired behavior. you just don't get php apparently

# ? Aug 5, 2012 21:21

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

MononcQc posted:

It's actually simpler using it. The example below creates a little hash with 3 users as keys, and the value for each is a list of their password and a secret to return whenever the password is right.

Here's the hash definition:
code:
(define users (make-hash (list (cons "tef" (list "password" "I Love Ruby"))
                               (cons "mononcqc" (list "hunter2" "I expect *******"))
                               (cons "vapid cutlery" (list "mylittlebrony" "IDGI")))))
The normal way to do things is then to:

Fetch the user from the hash

if it's there, extract the password and the secret from the value returned

if the password is the good one, return the secret, otherwise return 'false'

this is how it's done in racket:
code:
(define (login1 user pass)
  (let ([data (hash-ref users user 'undefined)]) ; fetch the entry
    (if (eq? 'undefined data)                    ; check if it's there
        #f
        (let ([passwd (car data)]                ; extract the password
              [secret (cadr data)])              ; extract the secret
          (if (eq? passwd pass)                  ; check if the password is right
              secret                             ; return the secret
              #f)))))
Using pattern matching, I can fetch from the hash, extract the values and compare them all at once

Here's the same function implemented using pattern matching:
code:
(define (login2 user pass)
  (match (hash-ref users user 'undefined)        ; fetch the value
    [(list (== pass) secret) secret]             ; deconstruct, compare & return
    [_ #f]))                                     ; not found
It's not hard to use, just somewhat harder to implement. Having pattern matching makes code much shorter and simpler at once.

E: usage
code:
> (login1 "bad user" "nknlk")
#f
> (login1 "tef" "password")
"I Love Ruby"
> (login1 "mononcqc" "heh")
#f
> (login2 "bad user" "kjdsf")
#f
> (login2 "tef" "password")
"I Love Ruby"
> (login2 "bad user" "kjdsf")
#f

it would be nice if you used a language that was actually relevant, or even comprehensible

# ? Aug 5, 2012 21:22

Zizzyx: Sep 18, 2007; INTERGALACTIC CAN CHAMPION

those loving parens everywhere

# ? Aug 5, 2012 21:24

Toady: Jan 12, 2009

but but learning lisp makes you a better programmer in all languages!

# ? Aug 5, 2012 21:25

MononcQc: May 29, 2007

vapid cutlery posted:

it would be nice if you used a language that was actually relevant, or even comprehensible

maybe if your lovely language of choice supported pattern matching I could show the features, but your language sucks because it doesn't have pattern matching.

# ? Aug 5, 2012 21:25

Zizzyx: Sep 18, 2007; INTERGALACTIC CAN CHAMPION

MononcQc posted:

maybe if your lovely language of choice supported pattern matching I could show the features, but your language sucks because it doesn't have pattern matching.

do one in haskell it probably has the least gay syntax

# ? Aug 5, 2012 21:26

salted hash browns: Mar 26, 2007; ykrop

i want to learn clojure but don't know where to start

# ? Aug 5, 2012 21:27

MononcQc: May 29, 2007

Languages that support pattern matching to some extent from the top of my head:

Racket, Erlang, Mercury, Haskell, OCaml, Mathematica, Elixir, REBOL, SNOBOL, Scala, SML, io, etc.

# ? Aug 5, 2012 21:28

Zombywuf: Mar 29, 2008

A better language would have:

code:

file_of_dicks(Name, Dicks) :-
   read_file(Name, Contents),
   process_dicks(Contents, Dicks).

> file_of_dicks("dicks.txt", Dicks).
no.

# ? Aug 5, 2012 21:29

Blotto Skorzany: Nov 7, 2008; He's a PSoC, loose and runnin'
came the whisper from each lip
And he's here to do some business with
the bad ADC on his chip
bad ADC on his chiiiiip

salted hash browns posted:

i want to learn clojure but don't know where to start

4clojure.org

# ? Aug 5, 2012 21:31

Blotto Skorzany: Nov 7, 2008; He's a PSoC, loose and runnin'
came the whisper from each lip
And he's here to do some business with
the bad ADC on his chip
bad ADC on his chiiiiip

did i ever mention that this

code:

Clojure> (cons 'foo 'bar)
java.lang.IllegalArgumentException: Don't know how to create ISeq from: clojure.lang.Symbol
Clojure> (cons 'foo '[bar])
(foo bar)
Clojure> (cons '[foo] 'bar)
java.lang.IllegalArgumentException: Don't know how to create ISeq from: clojure.lang.Symbol

is obnoxious? because it is.

# ? Aug 5, 2012 21:33

La petite z0rt: Aug 4, 2012

salted hash browns posted:

i want to learn but don't know where to start

# ? Aug 5, 2012 21:33

vapid cutlery

Apr 17, 2007

php:

<?
"it's george costanza" ?>

MononcQc posted:

Languages that support pattern matching to some extent from the top of my head:

Racket, Erlang, Mercury, Haskell, OCaml, Mathematica, Elixir, REBOL, SNOBOL, Scala, SML, io, etc.

drat. it's like the greatest hits of toy research languages

# ? Aug 5, 2012 21:33

MononcQc: May 29, 2007

Otto Skorzeny posted:

did i ever mention that this

code:

Clojure> (cons 'foo 'bar)
java.lang.IllegalArgumentException: Don't know how to create ISeq from: clojure.lang.Symbol
Clojure> (cons 'foo '[bar])
(foo bar)
Clojure> (cons '[foo] 'bar)
java.lang.IllegalArgumentException: Don't know how to create ISeq from: clojure.lang.Symbol

is obnoxious? because it is.

so what is this? clojure supports using cons, but not pairs? I guess that's a way to protect yourself from "lists that don't end right".

# ? Aug 5, 2012 21:34

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# ? Jun 11, 2024 16:16

Cocoa Crispies: Jul 20, 2001; Vehicular Manslaughter!; Pillbug

vapid cutlery posted:

drat. it's like the greatest hits of toy research languages

erlang's not so much a toy research language as a Serious Production Language for infrastructure like telephone switches

# ? Aug 5, 2012 21:34

The Something Awful Forums > Discussion > Serious Hardware/Software Crap > YOSPOS > p-lang thread: (now (have you (problems two)))

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