Live Code: Make a Programming Language From Scratch

Continuing on this series where I make a programming language from scratch, this time we implement dictionaries based on the tag feature we added in the last episode.

Transcript

The following transcript was automatically generated by an algorithm.

00:00 : hi there's Toby so I am going to
00:04 : continue the series where I create a
00:07 : programming language from scratch on
00:09 : stream only this time I'm not going to
00:11 : do it live because I found some
00:15 : connectivity issues with the streams
00:18 : lately it's the quality hasn't been very
00:22 : good so I'm gonna just record this one
00:24 : and then upload it one thing I want to
00:28 : bring to your attention is an
00:32 : enhancement to my website recently which
00:37 : is transcripts for videos so so if
00:44 : you're interested in this series for
00:46 : example you can click into the link for
00:51 : this video and you can see a transcript
00:54 : for this video and also this transcript
01:00 : is generated automatically by YouTube
01:03 : based on the audio and it may not be
01:07 : 100% accurate however I think I thought
01:12 : that it might be helpful for some folks
01:14 : because some of the videos some of the
01:17 : materials I make are quite long and with
01:21 : the transcript here you might be able to
01:22 : find just a bit you're interested in and
01:25 : skip to that part for example you can
01:28 : next to each line in the transcript
01:32 : there's this time marker here which you
01:34 : can click on and an editor jump the
01:39 : video there so yeah if that's
01:42 : interesting to you if you think that is
01:45 : helpful to you then it is there
01:48 : available for you ok let's get back to
01:51 : this series so in the last episode of
01:54 : this series which is episode 5 we
02:01 : implemented this curious concept I kind
02:05 : of invented on the fly which I called it
02:10 : tags which is kind of what they are
02:13 : now so this is an example of a tag you
02:17 : can you so this bracket curly bracket
02:22 : syntax I'm using it for various
02:26 : collection types that we have in this
02:28 : language and I realized that sometimes I
02:32 : want that to be in the array and other
02:34 : times I wanted that to be a set ID and I
02:37 : didn't necessarily I felt it would have
02:40 : been cumbersome to have a entirely
02:45 : different syntax for a set versus an
02:48 : array and I also kind of didn't want a
02:51 : function for some reason and why I kind
02:56 : of didn't when like in Python they would
02:58 : just say like hey just make a function
03:01 : that would initialize a set and then
03:04 : you're done for some reason I didn't
03:07 : feel like doing that so I said I'm gonna
03:11 : give it a tag whenever I write a
03:16 : collection that row like this and then
03:19 : the language would know which type of
03:21 : object it is so that's what I did and
03:24 : I'm planning to use that for
03:27 : dictionaries as well so a dictionary
03:29 : would look well although in the case of
03:33 : a dictionary you don't strictly have to
03:36 : use a tag because for dictionaries you
03:38 : can actually use two key value pairs
03:40 : syntax which will differentiate it from
03:44 : arrays and such so you can say like goes
03:51 : to 2 and then maybe 3 goes to 4 and so
03:57 : forth
03:58 : so that's a dictionary and because of
04:00 : the syntactic difference between this
04:03 : one versus this one you don't
04:05 : necessarily have to have a tag although
04:09 : if you use the tag it would also work so
04:13 : I think this time I'm going to implement
04:17 : dictionaries that's the plan so let me
04:19 : make a example of a dictionary so in I
04:24 : made a full example
04:28 : I made a full example here which does
04:33 : have this dictionary syntax so I'll use
04:37 : that so I make a file called example
04:43 : dict
04:44 : dot X so you can make a dictionary with
04:50 : this tag I was called this dict one and
04:55 : then maybe another one that where you
04:58 : don't use the tag so that we have those
05:01 : cases accounted for one thing I do want
05:06 : to do with this dictionary
05:07 : implementation is that I want the keys
05:13 : to be able to have any type unlike
05:17 : JavaScript where the key can only be a
05:21 : string I want this to be more like
05:26 : Python where the key can be a number or
05:31 : a string or even an object another
05:34 : dictionary or an array all of those
05:37 : things are allowed let me get rid of
05:40 : this activity bar kind of there's a
05:44 : little bit distracting so I'm gonna get
05:46 : rid of that so and internally I'm
05:51 : planning to use the hikmah script map to
05:56 : implement it which does allow for keys
06:01 : of various types so if you search for
06:03 : mdn map
06:15 : the way you make a map is with the new
06:18 : map constructor you're not supposed to
06:22 : access it like this though does he sit
06:26 : there saying this is still sort of works
06:29 : but doesn't behave as expected you're
06:32 : really not supposed to do this that this
06:35 : mean we got these red lines next to
06:39 : these code example you're not supposed
06:40 : to do this don't do this you're supposed
06:42 : to call a map that's set to to update
06:47 : entries in the map and map that get I
06:51 : believe yeah map that get to an access
06:56 : increase within the map and again the
07:00 : key can be objects or other types of
07:02 : values and that's fine so that's what
07:05 : we're gonna use internally for our
07:07 : dictionary implementation I think it's
07:09 : gonna be great so first we're gonna need
07:14 : to implement the parser so let's go into
07:20 : the grammar
07:23 : whoo this is some grammar so we have
07:31 : statement and a statement can be an
07:35 : assignment a function call of function
07:37 : definition we have expressions I think
07:43 : that's what we are looking for there's
07:45 : an expression there's an expression so
07:48 : what can an expression be it can be a
07:50 : identifier a literal a function call a
07:52 : code block we want to go for a literal
07:56 : we have a sequence literal but you which
08:00 : used to be a string literal but at this
08:02 : point the sequence can either be a a
08:11 : sequence is either an array or a set
08:17 : maybe in the future there can be other
08:20 : things too maybe like a linked list
08:21 : could could be a sequence as well but
08:30 : this time we're really concerned with
08:32 : dictionaries so what I'm gonna do is add
08:35 : a dictionary literal to the mix and
08:44 : define the grammar for that it will have
08:53 : an optional tag as well I believe it's
09:09 : this this series has been on hiatus
09:13 : having to remember how I do things so
09:18 : we're going to allow an optional tag if
09:22 : they don't provide the tag this will
09:24 : just be represented as a null value so
09:27 : my AST sort of converter has to know
09:33 : that somehow I think it defaults to some
09:41 : tag maybe I don't remember oh yeah here
09:44 : it defaults to array in the instance of
09:47 : the sequence but for a dictionary
09:50 : actually I mean for dictionary I don't
09:54 : know if there are can be different types
09:57 : of dictionary so whatever the dictionary
10:02 : is also going to be enclosed in curly
10:05 : brackets and then we're gonna have some
10:09 : optional whitespace and then we'll have
10:12 : a collection of key value pairs
10:18 : I'm gonna call this key value pair less
10:24 : perhaps and then we're gonna write a
10:31 : converter for it but I found before that
10:34 : I'm also gonna write the I'm gonna write
10:39 : this definition for key value pair list
10:42 : first but before that I'm going to write
10:45 : the syntax for an empty dictionary oh oh
10:53 : for the empty dictionary is when you
10:56 : will actually need a tag yes actually
11:01 : you know what maybe I should not wait we
11:15 : have houston we have a problem because
11:19 : mmm let me think about this
11:25 : so so the parser will recognize this as
11:31 : a sequence literal actually so there's
11:39 : an ambiguity in the language if I were
11:42 : to add this clause so one way to think
11:46 : about it is
11:53 : the only way to think about it is well
11:55 : this guy is not necessarily a sequence
11:59 : literal is it it's a it's a collection
12:03 : because it a sequence is only a set so
12:07 : like the sequence is either an array or
12:10 : a set but a let's say a collection is
12:14 : either a sequence or a a dictionary just
12:21 : say that is that fair I mean I'm making
12:27 : this up so I can say so I'm gonna
12:29 : actually redefine or rename this guy to
12:36 : something I'm gonna call this the empty
12:38 : collection empty collection literal
12:43 : actually yeah
12:52 : empty collection literal and I'm gonna
12:56 : say yes yes yes this is what I do
13:00 : yes this is good this is good like this
13:04 : so I'm gonna separate the empty
13:07 : collection literal from the sequence
13:10 : literal in the dictionary literal so an
13:14 : empty collection letter is neither of
13:17 : those
13:25 : yeah I think that's a good way to handle
13:28 : this but if the tag name of an empty
13:32 : collection literal is a tip done that
13:41 : should be yellow and I'm gonna say it's
14:02 : a dict literal and then it's entries
14:15 : will be maybe this can even be value
14:28 : I think entries should also be on array
14:40 : because I will say it's a array of array
14:47 : of two I wanna erase that's what this is
14:55 : meant to be it's an array of two element
14:58 : arrays where the for each containing two
15:02 : element array the first entry is the key
15:06 : and the second entry is the value so
15:11 : let's do it like that
15:13 : so the yeah how call this entries it's a
15:18 : dictionary literal else
15:22 : it's either a set literal or an array
15:25 : literal and it's got items instead of
15:28 : entries okay that's good with that I
15:33 : think that's okay and then now for the
15:36 : dictionary literal so let's define the
15:39 : key value pair list I think that would
15:45 : be it's either a key value pair or or
15:55 : it's a key value pair and then some
16:00 : mandatory whitespace and then another
16:03 : key value pair list that comes after it
16:08 : but what is a key value pair well a key
16:12 : value pair is a expression
16:19 : thank you and then some optional
16:21 : whitespace a : some optional whitespace
16:24 : and now another expression I think
16:27 : that's what a key value pair is so yeah
16:32 : I think that probably it's right so and
16:39 : there are no commas by the way so so
16:45 : yeah this is what I envision as a
16:46 : dictionary oh shoot in order to allow a
16:51 : newline character here inside the
16:55 : whitespace I think I actually need to do
16:58 : some extra thing in order to handle that
17:11 : hmm
17:14 : I'm gonna T for that so for now I'm just
17:17 : gonna do this something like this I want
17:27 : one tip for
17:32 : for programmers out there is um try to
17:37 : do one thing at a time
17:38 : don't don't overwhelm yourself by doing
17:43 : multiple things at once so this is what
17:45 : I'm doing instead of trying to handle
17:47 : that extra case that I just realized I
17:51 : needed to handle I'm gonna defer that
17:53 : and just handle the this syntax with
17:56 : without the newline without the
17:59 : possibility of new lines in there
18:01 : because that's another piece of
18:03 : complexity that I would have to deal
18:05 : with and it would be easier to deal with
18:07 : it separately on his own once I'm done
18:10 : with this particular task that I'm on so
18:14 : let's just try this I'm gonna write the
18:17 : converters for each of these grammar
18:21 : rules to convert the bits to a
18:25 : JavaScript object an ast representation
18:29 : so I think I'm gonna for a key value
18:33 : pair I think I'm just gonna represent it
18:35 : as like a two element array like that
18:52 : get data alright as I said and then the
19:05 : key is gonna be the 0 1 2 3 4 for that
19:16 : data okay so that's the key value pair
19:23 : and then here I'm going to represent a
19:27 : key value pair list as an array of these
19:32 : are rice array of two element arrays so
19:35 : it would it look like
19:40 : e - value - etc okay so in the case of
19:49 : the sing the singular case where we have
19:53 : one single key value pair I'm gonna do
19:59 : eat hung an array that wraps around
20:03 : whatever that guy returns which would
20:05 : look like that so but I do have to unbox
20:10 : it because this guy would come in an
20:13 : array with just that one element in it
20:15 : so I'm gonna unbox that I guess I could
20:19 : have just returned data and it would
20:22 : have done the same thing but I think
20:23 : this is more explicit and that's fine
20:28 : for this case you still have to return
20:37 : an array I think I'm gonna use two fancy
20:39 : array spread operation but the first
20:43 : entry is gonna be the zero element of
20:46 : data that's an array that I do not want
20:49 : to spread but the result of that is the
20:52 : one that I do want to spread so that
20:54 : would be in index zero one two okay so I
21:02 : know that this guy is going to return on
21:05 : our Ray as long as I make both of these
21:09 : cases of the rule return an array which
21:13 : I have done so that returns an array and
21:15 : that returns and right so this guy's
21:17 : come in return on a right I get the
21:18 : array spread it into this new array
21:21 : which has this thing in the beginning
21:24 : that should get us another finally have
21:33 : this dictionary literal
21:40 : for dictionary literal I will never
21:42 : return something like this except the
21:44 : entries is should be what came back from
21:48 : here so I do want to verify that the tag
21:53 : that we got the tag name that we got I
22:02 : want to verify that is a dictionary so
22:07 : it's not a problem and we're just gonna
22:13 : throw a say what did I say last time tag
22:19 : a sequence as a dict I'm gonna say tag a
22:28 : whatever you named it okay so it has to
22:36 : be dict
22:36 : if we have a dictionary literal but if
22:39 : you have an empty one then you can don't
22:43 : know whether it's a dict or an array or
22:45 : a set so we're gonna default that to
22:49 : array if you don't tell us but if you
22:54 : want an empty date you have to tag it
23:01 : say dig three is an empty dick so that's
23:05 : not gonna be a date that's gonna default
23:07 : to be in the array all right so you have
23:10 : to tag that as a dick that's how it
23:12 : works
23:15 : okay so I really like the aspect of this
23:23 : project that I'm just making stuff up on
23:26 : the fly without being concerned about
23:31 : whether it's a good idea or not in the
23:33 : long run because this this project is
23:37 : meant to be a toy project so you can
23:39 : kind of improvise without much bad
23:45 : consequence
23:47 : or I should say mistakes will have
23:49 : little consequence so here I want to
24:00 : return hey wait a minute this code needs
24:04 : to go inside the arrow function I
24:10 : realized I don't have the nearly GS
24:14 : syntax highlighter that's okay the
24:25 : object whose type is stick and its
24:31 : entries you're gonna be whatever that
24:34 : guy returns which will be index 0 1 2 3
24:40 : so data data index 3 ok so that's my
24:47 : dick literal we're gonna test the parser
24:53 : by itself see if that worked before
24:58 : before adding the feature in code
25:02 : generator let's do that so I'm gonna
25:09 : have this directory is getting too messy
25:12 : so I may clean it up soon but for the
25:17 : moment though the example I want is dict
25:20 : example so I'm gonna do new parse yes
25:25 : take the example it doesn't like it it
25:30 : oh I need to generate the parser and PM
25:33 : run gen parser which runs the nearly
25:37 : compiled now I'm gonna press it again
25:41 : still doesn't like it why is that
25:45 : did I put the dictionary literal in the
25:50 : list I did
26:20 : Oh Oh it's the lexer this is a lecture
26:23 : ever so I need to teach the lexer to
26:28 : parse the :
26:30 : so that's easily fixed okay because
26:39 : we're using Mooji s as the lecture that
26:43 : pre-processed the string input before it
26:47 : gets into the grammar the lecturer needs
26:49 : to understand every type of character
26:52 : that goes into the source files
26:55 : so hopefully this fixes a tact dict as a
27:00 : dict okay i tacked a dict as a dict I
27:06 : mean that seems good right if it the tag
27:14 : name is not dict didn't throw the error
27:19 : but you told me it's dict so I don't get
27:26 : it
27:34 : which line 134 it could be coming from
27:44 : okay I could look at Grandma GES line
27:50 : 134 even though I didn't write this code
27:53 : so this is 40 so this we usually don't
27:58 : look at this grammar that tree s file
28:00 : usually we only look at this grammar
28:02 : that any file but we're gonna look at it
28:05 : now because we're try this grammar file
28:09 : when nearly compiles the grammar file it
28:11 : translates it into this javascript file
28:14 : which is where the line number of the
28:17 : error is so we might as well make use of
28:20 : that line number and try to get a clue
28:22 : to what's going on I believe this is
28:28 : curious I believe this is coming from
28:33 : this line of code it just looks just
28:36 : like that code but it says tagged dick
28:40 : as a dick I'm only going to throw it if
28:48 : it's not a dick it is a dick why would
28:53 : you why would you enter this so what I'm
29:01 : gonna do is console that log chase the
29:09 : way it'll put quotes around it so in
29:11 : case
29:18 : oh I see because it's a token object not
29:25 : a string literal I think I get it
29:34 : maybe
29:47 : it is it is a token object that's a
29:54 : stick in it in the lecture I had the the
30:00 : same sign and greater than sign defined
30:06 : so I guess it's saying this guy is a
30:11 : actually a token literal I imagine if
30:15 : that's the case and that it's wrong here
30:17 : as well so we may need to fix that in
30:21 : both scenarios another way I could fix
30:26 : it is just fix it in this optional test
30:29 : the definition of the optional tag
30:31 : because I imagine when I get this tag
30:37 : well actually here I could fix it here
30:41 : so this guy I imagine it's going to be
30:46 : an object I'm gonna print it out let's
30:49 : see I'm gonna return it but I'm gonna
30:58 : out the fact that I have a tag I think
31:05 : it's an object I think I already removed
31:15 : that print out I'm gonna because I
31:19 : edited the grammar file and not the GS
31:22 : file I'm not close to J's file so I
31:24 : don't get confused I'm just gonna work
31:27 : on there and grammar file now after I
31:29 : edit and save the grammar file I have to
31:32 : remember to run
31:33 : the jhen parser come in and then now I'm
31:41 : gonna try to parse it again and yeah it
31:44 : does say when it encounters attack it
31:48 : it's a token object so I'm just gonna
31:51 : pick the either the value property or to
31:55 : text property out of it it doesn't
31:58 : matter which one I pick the value
32:03 : property out of it so the rest of my
32:06 : code can sort of happily be ignorant
32:11 : about that and treat that as a string
32:15 : that is the tag name and I think that
32:20 : should work now although I would say
32:27 : previously I did test the set
32:40 : just to set actually work or not oh I
32:48 : know I worked ok ok because the token
32:55 : object has a two string method yeah so
32:59 : that even if this guy was a token it
33:03 : would successfully concatenate with this
33:05 : because the token object has a two
33:08 : string method there well when you
33:10 : concatenate the token object with
33:13 : another string it'll use the two string
33:15 : method to convert to can into a string
33:17 : first okay in any case I think what I've
33:21 : done is kosher so I'm gonna go with that
33:25 : and now it it was able to create an ast
33:30 : let me examine that ast file and see if
33:34 : it's good excuse me okay so this is the
33:48 : do it side by side
33:57 : all right so this is the program where
34:00 : we have a variable assignment variable
34:03 : name is dict 1 and then the value we're
34:08 : assigning to it is a dict literal which
34:10 : is correct and within it
34:13 : we got entries the first entry has two
34:16 : things within the entry the first one is
34:19 : a token it's a number and it has the
34:23 : value of one looks right so three and
34:30 : four that looks right the second
34:32 : assignment assigning to dick 2 is also a
34:35 : dict literal we have a string literal as
34:41 : the key and a number as the value and
34:44 : then second entry string literal is a
34:47 : key number is a value third one dick
34:50 : three also a dict literal this time with
34:53 : no entries great that worked then I
34:58 : retest the array example I think make
35:02 : sure that stuff still works I don't
35:07 : imagine that I would have broken it but
35:10 : you never know so three-part the array
35:15 : example and let's do the same exercise
35:20 : so the example array okay it's s T so
35:34 : the first one is an assignment to a
35:36 : variable called R and the value is an
35:41 : array literal with a bunch of number
35:43 : tokens in it that looks right to me
35:48 : okay I think the tag example is probably
35:53 : what I want so yeah a dick equals so
36:00 : this should be a dick
36:01 : so like something like maybe age nope
36:17 : nope no comma age maybe but if you have
36:23 : an empty dick empty array empty eraser
36:32 : like that that empty set looks like this
36:38 : you have to tag the empty set and an
36:40 : empty dick looks like that if it's empty
36:45 : you have to tag it otherwise it will
36:47 : default to an array okay so that's how
36:50 : it works
36:51 : Oh tag the empty array too just to be
36:57 : explicit
36:59 : so let's parse this one
37:09 : okay so we have a tag all right let's do
37:15 : the same exercise we're going to look at
37:17 : them side by side okay so we are signing
37:23 : to in the variable called a array the
37:28 : value is an array literal with numbers
37:32 : three numbers looks good
37:35 : we're assigned to a set and the value of
37:37 : that is a set of literal with three
37:41 : numbers okay that's that one and then we
37:45 : have a array two that's an array literal
37:48 : again good and then we have a dick
37:52 : this time it's a dict literal dick
37:56 : literal with these entries string name
37:59 : and a string Maria and the string age
38:01 : and a number ten perfect and then we
38:05 : next with empty array is an array
38:08 : literal with zero items in it that looks
38:11 : good empty array tag same thing and then
38:17 : empty set
38:18 : he's a set literal with no items in it
38:20 : and then an empty dick is a dick literal
38:23 : with no entries in it so oh that looks
38:26 : great so now I'm gonna go ahead and work
38:29 : on the code generator which is in
38:37 : degenerate yes file so this code at the
38:45 : moment is actually very very minimal
38:47 : which is great
38:51 : so for those of you who are following
38:55 : along this is a great state of things
38:59 : because you can read through this code
39:01 : and and without too much difficulty
39:05 : understand what's going on
39:08 : so this there's a top level generate
39:11 : function which takes a top-level ast and
39:14 : generates JavaScript JavaScript program
39:18 : out of it basically and so what we need
39:22 : to do is basically at another condition
39:26 : that knows how to handle dict literals
39:32 : what I'm gonna do is just instead of
39:37 : adding that code I'm gonna just try
39:45 : running the generator and and see it hit
39:49 : the error first there that's unknown
39:52 : node type dick literal it hit this error
39:55 : here so that is supposed to prompt me to
39:58 : hey you need to handle the deed that
40:02 : node type so I'm going to add a clause
40:04 : here
40:12 : and I'm gonna generate a new map
40:16 : expression basically here's the plan
40:21 : so let me think I'm gonna do a map over
40:26 : the entries so note that entries we can
40:34 : look at the DST while we write this code
40:46 : I mean look for a dick literal so a dick
40:53 : literal is gonna have this entries
40:56 : property in it and that's the one I'm
40:58 : going into and because the entries the
41:02 : value inside that property is Marais
41:04 : over and then each entry is going to be
41:15 : an array of links to each entry it's
41:19 : gonna look like that so the key is gonna
41:22 : I can actually use this array descriptor
41:26 : assignment like this I can't even do
41:31 : that in the parameter list but I don't
41:33 : feel like doing it here because the line
41:35 : is already kind of long all right well
41:39 : in this split-screen scenario we don't
41:41 : have damage more room anyway so we have
41:47 : key and value D structure now key is
41:50 : gonna be an object an expression in this
41:54 : case it's a string literal but it
41:56 : doesn't have to be and also in this case
42:00 : it's a also a string but again it
42:03 : doesn't have to be so we're just gonna
42:05 : ask our our generate function to
42:13 : generate the JavaScript version for us
42:15 : so I'll say Jes key say key expression
42:26 : key expert for short is the result of
42:30 : generating the JavaScript code for the
42:33 : key and the value expert will convert
42:49 : this token object or ast this could be
42:54 : actually a more complex expression like
42:58 : a 1 plus 1 or something
43:02 : uses the generator function to convert
43:04 : that into a expression which is in
43:07 : JavaScript and then given that we're
43:10 : gonna actually format that into this
43:12 : JavaScript array that has length of 2 so
43:16 : we're gonna format it into basically in
43:20 : this scenario it would look like
43:30 : so we want to format like this and then
43:33 : so for each entry in the map we format
43:36 : it like this and then finally for
43:38 : multiple entries it would look like an
43:40 : array of multiple arrays like that so
43:47 : the way I'll do that is using this
43:53 : template string syntax and finally when
44:05 : we receive all the entries in an array
44:08 : we'd use
44:09 : join to put a comma in between them and
44:14 : then after that we're gonna make a
44:17 : statement that creates a new map and
44:25 : then puts those entries within it so let
44:28 : me try generating the code now just
44:34 : looking good to me a real example tag so
44:37 : let me look at example tag Jas that
44:47 : looks great to me that's that's how
44:49 : you're supposed to instantiate a map so
44:53 : yeah so that looks like it worked you
45:01 : know execute the program
45:08 : Dex maybe I will even print out the map
45:18 : he picked I mean yeah the dict in my
45:24 : language I'm calling them dick
45:26 : dictionaries but in JavaScript it my
45:29 : script it's called the Mac II I'll print
45:37 : out a dict as well as empty dick and
45:41 : yeah we got these maps great that's
45:45 : exactly what I wanted okay so now in
45:48 : order to make the dictionaries actually
45:51 : operational we want to be able to loop
45:55 : through them access set values in them
46:00 : get values from them at the moment our
46:06 : paradigm has been just provide run time
46:09 : functions to do that and I think our
46:13 : runtime file so let's just here might
46:26 : extract this Bing big string literal
46:30 : maybe into a separate file let's go
46:33 : ahead and do that I'm gonna do make a
46:35 : run time is extract this big string
46:42 : literal into it
46:49 : the possibly I might just let me think
46:53 : about this actually think I should just
46:58 : yeah make this file a little JavaScript
47:03 : file like this and then when generate
47:07 : needs to use it I'm just gonna use the
47:10 : file system to read in this runtime j/s
47:26 : to make sure I read the file that's
47:31 : right in the same directory as this is
47:34 : the script itself which in this case is
47:37 : the generator yes I'm gonna use the der
47:39 : name yes so just reach the file for me
47:55 : and then I'm gonna do two string I did
48:02 : it
48:13 : oh I did need a third parenthesis okay
48:20 : because of this caught pass joint okay
48:25 : so now I think this one time oh this one
48:31 : time is needed by this generate function
48:35 : here either pass them in but I don't
48:48 : feel like it right now so I'm just gonna
48:50 : make a global variable I'm gonna make a
48:54 : run time this global variable which I
48:58 : will set up here it's only reference one
49:03 : time so I kind of feel okay not too bad
49:10 : about doing it although in general it's
49:14 : not really a good idea okay so let me
49:20 : try this okay we still get what we have
49:26 : so now yeah not feeling great about
49:36 : having this global variable honestly I
49:40 : could do read file sync instead I
49:46 : thought that's actually slightly better
49:49 : so I'm going to do that
49:53 : so I'm gonna do it like this three files
49:57 : think I'm gonna use the read file sync
50:03 : function and read in the file outside of
50:15 : this pain function it is also not great
50:20 : but I feel like slightly better okay I
50:29 : feel like this is slightly better
50:31 : because it's a constant
50:34 : okay and I think the use of refile the
50:39 : synchronous reading of file is it's kind
50:43 : of okay
50:44 : in this scenario where we sort of do
50:49 : need to stop the world and read in that
50:51 : file okay so so now we have a run time
50:58 : GS which contains all the JavaScript
51:02 : functions that will be available to the
51:04 : run time when the when did transpiled
51:10 : javascript is running we're gonna add
51:13 : some functions to work with dictionaries
51:19 : probably the way you iterate
51:25 : dictionaries I believe is you can call
51:30 : its entries method I think you can call
51:38 : map that increase so I'm gonna allow it
51:43 : the iteration of a dictionary aka map
51:48 : did this too just so that it I want to
51:53 : reiterate what I call indict that's the
51:58 : same as a map map is es hikmah script
52:04 : term
52:05 : and in my programming language called X
52:08 : I'm gonna call it dict
52:11 : but I guess in in the context of what
52:16 : we're doing here these two guys are
52:19 : interchangeable dict means a map and
52:22 : vice versa
52:25 : okay so I'm gonna make a function called
52:28 : entries given a dict it's gonna return
52:44 : map that entries which I believe it's an
52:49 : iterator which is we don't have the
53:03 : concept of iterators in this language
53:06 : yet but if I do add it now I could do
53:15 : one thing at a time okay and then now
53:20 : that you can now you can just call
53:22 : entries on the dict and then after that
53:25 : you can do all of these other things to
53:28 : it you can normally do with an array you
53:37 : might need something for iterating over
53:39 : a set as well but I'm gonna defer that
53:42 : but with a dictionary what you really
53:45 : want to use is get in set so I'm gonna
53:50 : get a key get by a key and then you put
54:02 : a key provide a key and a value there
54:06 : you
54:07 : into that tea and you call that set like
54:16 : that yeah so that's how to work with the
54:22 : dictionaries so I think we're ready to
54:25 : write a simple example of using a
54:29 : dictionary so let me think do we have a
54:34 : split function for Strings
54:45 : okay let's add a split function give it
54:53 : a string and a separator string that
55:00 : split the separator you have to wrap all
55:05 : these native methods with functions
55:07 : because the programming language only
55:09 : has functions at the moment it does not
55:11 : have methods so if we have split I'm
55:17 : thinking maybe we can I'm jumping ahead
55:23 : actually so let me do something like
55:25 : this I can set the entry set with Indic
55:36 : 3 getting it back out from language
56:11 : that's a design decision that I made
56:14 : early on so that works yeah we're able
56:17 : to set a dictionary and get a dictionary
56:22 : I really could get the size of a
56:24 : dictionary what about the size of an
56:27 : array
56:36 : let's add that how do you get the size /
56:40 : array is it that size that size yes
56:48 : there's a dot size for rape it would be
56:56 : that length
56:57 : what about set
57:04 : I just had an idea which is kind of
57:10 : exciting I think set also has a size
57:15 : okay so for all the collection types
57:20 : that for which we can get a size or
57:23 : length whatever it's kind of weird that
57:27 : format and set its size but for four
57:35 : rays it's called links right so if we
57:40 : can somehow unify it so that you know
57:45 : there's there's a same function you call
57:47 : to get the size of any collection tip
57:50 : that would be pretty cool and enclosure
57:55 : they have a concept called protocols
57:58 : which is a feature that we can implement
58:04 : in this language and I think there would
58:07 : be a lot of fun to try to implement that
58:09 : because I wrote a blog post a while back
58:12 : that talked about this idea that just
58:23 : works 2015 that talked about this idea
58:29 : and within it I even sort of imagined a
58:33 : language feature if we were to extend
58:37 : JavaScript to have this protocol feature
58:40 : it sort of imagined what it would look
58:43 : like and now that we're actually able to
58:46 : build a programming language from
58:50 : scratch we actually have the ability to
58:52 : do this so I think this is very exciting
58:54 : but again one thing I learn so I'm gonna
58:59 : make a size function which takes either
59:03 : a set or a map size
59:14 : the bet for a race does a separate one
59:17 : called length and that's gonna return
59:21 : our a downlink and for the moment it
59:24 : kinda and yeah I could make the same
59:29 : function handle both of them but for now
59:32 : I'm not gonna do I could have written an
59:35 : if statement here and have one of the
59:37 : functions handle both of them so now I'm
59:40 : gonna differentiate it I think so now
59:44 : I'm able to print the dick has it has
59:55 : size of dick three entries you know size
1:00:09 : is not a function I thought size was a
1:00:14 : function and looked up the docs man I
1:00:17 : totally looked it up like there's a map
1:00:20 : that size man oh it is not a function
1:00:28 : it's a property
1:00:30 : it's a magical property okay
1:00:38 : did not know that
1:00:40 : okay so the dick has one entries in it
1:00:49 : on it like septic three
1:00:59 : out then I should have two entries in it
1:01:05 : okay great and we can also we can
1:01:10 : iterate through the entries because we
1:01:13 : can do entries of dict three and that
1:01:17 : would give us an array and an array of a
1:01:22 : race I believe and we can do a map you
1:01:27 : think so
1:01:31 : maybe also at a keys function but for
1:01:34 : now I would say each each takes a block
1:01:41 : I think and then it can have argument I
1:01:45 : think like this like this so for each
1:02:09 : entry and dick three let's just print
1:02:13 : out the key we'll do an equal sign like
1:02:18 : that and the value let's see if that
1:02:21 : works
1:02:23 : no it does not
1:02:26 : it's a parse error it doesn't look this
1:02:29 : one like this oh we don't we don't have
1:02:34 : this index okay we don't have a way to
1:02:42 : access an index yet oh that is freaking
1:02:48 : hilarious now we do actually not an
1:02:54 : array index we need to index notation
1:02:58 : but that's not been implemented so maybe
1:03:01 : I make a function called at at zero
1:03:09 : so let's go make that function you had
1:03:14 : to make things as you need them so like
1:03:18 : you have an array does this how you do
1:03:30 : it okay let's see if that works
1:03:32 : oh that works great beautiful I don't
1:03:39 : need this extra space because also that
1:03:43 : lock will automatically put in spaces so
1:03:46 : yeah this iterates through all the key
1:03:49 : value pairs within the dictionary and we
1:03:53 : have a way of iterating through
1:03:55 : dictionaries now this is great so okay
1:03:59 : so we've accomplished what we wanted
1:04:02 : which was to implement dictionaries in
1:04:04 : this language yeah I'm pretty satisfied
1:04:08 : with this so I'm gonna stop the stream
1:04:11 : here and I hope to see you next time

Live Code: Make a Programming Language From Scratch - Part 6

Transcript