Make an interpreter for yes!

Question

Yes is a stack-based ~~language~~ that has a few space-separated instructions:

yes: Push 1 to the stack
no: Push 0 to the stack
what: Push the input to the stack (input is taken at the start of program execution and is the same for the whole execution)
sure: Increment the last item in the stack
nah: Decrement the last item in the stack
really: If the last stack item is a number, replace it with its Unicode character. If it is a letter, replace it with its Unicode char code.
oh: convert the stack to strings and concatenate it, and push that to the stack.
nope: remove the first stack item
yep: remove the last stack item

The stack's last element is always outputted at program end. All non-alphanumeric and non-space characters are ignored. All code is lowercase. Example programs:

yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
oh

prints Hello, World!.

what

prints the input (cat program.)

no nah

prints -1.

no really

prints the NUL character (U+0000)

what 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
oh

prints the input and an underscore.

yes no nope

prints 0

yes no yep

prints 1.

You must write an interpreter in as few bytes as possible. Here's a JS implementation (not well golfed!):

function yes(code, input){
	var stack = [];
	var functions = {
		"yes": "stack.push(1)",
		"no": "stack.push(0)",
		"what": "stack.push(input)",
		"sure": "stack[stack.length - 1] ++",
		"nah": "stack[stack.length - 1] --",
		"really": "stack[stack.length - 1] = (typeof lastItem === 'number' ? String.fromCharCode(lastItem) : lastItem.charCodeAt())",
		"oh": "stack.push(stack.reduce((x, y)=>''+x+y))",
		"nope": "stack.shift()",
		"yep": "stack.pop()"
	};
	code.replace(/[^a-z ]/g, "").split(" ").map(x=>(lastItem = stack[stack.length - 1],eval(functions[x])));
	return stack[stack.length - 1];
}

textarea{
  display: block;
}

Code: <textarea id = "code"></textarea>
Input: <textarea id = "input"></textarea>
<button onclick = "output.value = yes(code.value, input.value)">Run</button>
<textarea id = "output"></textarea>

Edge cases

yes yes oh prints 11.
Intput may be a string or number.
The code can contain any chars. Ones not matching [a-z ] should be ignored.

Please make sure that your testcases include all of the commands. — Leaky Nun, May 6, 2017 at 12:54
What type of integers should be used? Is there overflow? What does really do if there is a multi-character string on top of the stack? — Martin Ender, May 6, 2017 at 13:03
Is it okay if we assume that the input only contains can character in [a-zA-Z ]? — user41805, May 6, 2017 at 14:14
Push the input Can input be numbers? Arrays? Chars? Strings? If so, can input strings be multi-line? Increment the last item in the stack What does this do when the last item is not a number? — Luis Mendo, May 6, 2017 at 15:02

Arnauld · Accepted Answer · 2017-05-08 18:30:22Z

JavaScript (ES6), 218 215 204 203 bytes

Takes the program string s and the input i in currying syntax (s)(i).

s=>i=>s.replace(/\w+/g,S=>(c=eval("[P()];P()+1;[s.shift()];1;0;s=[s.join``];P()-1;i;P()[0]?k.charCodeAt():String.fromCharCode(k)".split`;`[parseInt(S,35)%156%9])).map||s.push(c),s=[],P=_=>k=s.pop())&&P()

How?

We use the perfect hash function parseInt(S, 35) % 156 % 9 to convert the instruction S into an index in 0…8 and use this index to select the JS code to be executed:

instruction | base 35 -> dec. | % 156 | % 9 | JS code
------------+-----------------+-------+-----+---------------------------------------------
"yes"       |           42168 |    48 |   3 | 1
"no"        |             829 |    49 |   4 | 0
"what"      |         1393204 |   124 |   7 | i
"sure"      |         1238209 |    37 |   1 | P()+1
"nah"       |           28542 |   150 |   6 | P()-1
"really"    |      1439554619 |    35 |   8 | P()[0]?k.charCodeAt():String.fromCharCode(k)
"oh"        |             857 |    77 |   5 | s=[s.join``]
"nope"      |         1016414 |    74 |   2 | [s.shift()]
"yep"       |           42165 |    45 |   0 | [P()]

The P function pops the last item off the stack s and loads it into k.

We prevent the result of some instructions from being pushed back onto the stack by testing if the .map() method is defined, that is, if the result is an array. The code for oh is returning an array by design and we force nope and yep to return arrays as well. Hence the syntax:

(c = eval("[code0];code1;...".split`;`[index])).map || s.push(c)

Test cases

let f =

s=>i=>s.replace(/\w+/g,S=>(c=eval("[P()];P()+1;[s.shift()];1;0;s=[s.join``];P()-1;i;P()[0]?k.charCodeAt():String.fromCharCode(k)".split`;`[parseInt(S,35)%156%9])).map||s.push(c),s=[],P=_=>k=s.pop())&&P()

console.log(f(`yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
oh`)())

console.log(f(`what`)(1234))

console.log(JSON.stringify(f(`no really`)()))

console.log(f(`what 
yes sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure sure really 
oh`)('code golf'))

console.log(f(`yes no nope`)())

console.log(f(`yes no yep`)())

Community · Accepted Answer · 2020-06-17 09:04:33Z

Röda, 256 bytes

f c,n{s=[];(c/`\W|_`)()|{|m|s+=#m-2 if[m=~"yes|no"];s[-1]+=#m*2-7 if[m=~"sure|nah"];s+=n if[m="what"];s=s[#m%3:#s-#m%2]if[m=~"nope|yep"];{s+=""s()|s[-1].=_}if[m="oh"];{t=s[-1]y=t..""a=t+0;a=a..""{s[-1]=ord(s)}if[#a>#y]else{s[-1]=chr(t)}}if[#m=6]}_;[s[-1]]}

Try it online!

Explanation

#variable returns the length of variable (if it is a string or an array).

f c,n{                         /*declare a function f with arguments c and n*/
s=[];                          /*initialise the stack*/
(c/`\W|_`)                     /*split the code on anything not [a-zA-Z0-9]*/
          ()|                  /*and push each of its values to the stream*/
{|m|...}_                      /*for each element m in the stream, do:*/
s+=#m-2 if[m=~"yes|no"];       /* add 1 or 0 to the stack if m is "yes" or "no"*/
s[-1]+=#m*2-7if[m=~"sure|nah"];/* increment or decrement the top element if m is "sure" or "nah"*/
s+=n if[m="what"];             /* push input if m is "what"*/
s=s[#m%3:#s-#m%2]              /* remove the first or last element of the stack
  if[m=~"nope|yep"];           /* if m is "nope" or "yep" */
{                 }if[m="oh"]; /* if m is "oh" do:*/
 s+=""                         /*  add an element to the stack*/
      s()|s[-1].=_             /*  for each element in s, concatenate that amount to the last element of the stack*/
{                   }if[#m=6]  /* if m is "really" (it's length is 6) do:*/
 t=s[-1]y=t..""                /*  get the last element of the stack*/
 a=t+0;a=a..""                 /*  add 0 to it, if a is a number, this does nothing, otherwise this makes a longer by 1 character*/
 {s[-1]=ord(s)}if[#a>#y]       /*  if a is longer than t (the last element is a char/string) replace it with its code point*/
 else{s[-1]=chr(t)}            /*  otherwise, replace the last element with the char it represents*/
 [s[-1]]                       /*finally output the top of the stack*/

Okx · Accepted Answer · 2017-05-18 15:18:21Z

3

05AB1E, 77 67 63 61 bytes

Að«Ã#vyÇO§}ðý•9ǝ×н}ÀÀÙ™Íð•650в"X ¾ I > < DdiçëÇ} J r\r \"#:.V

Assumes the program is on the top of the stack.

Try it online!

edited May 18, 2017 at 15:18

answered May 8, 2017 at 8:20

Okx

16.4k5 gold badges42 silver badges111 bronze badges

\$\begingroup\$ Can you really assume that all input is valid? For example that you can't get the program yes no sey yep \$\endgroup\$
– Emigna
May 8, 2017 at 11:36
\$\begingroup\$ @Emigna There are no test cases about this, no specifications, and the OP hasn't clarified this even after somebody has left a comment. \$\endgroup\$
– Okx
May 8, 2017 at 12:14
\$\begingroup\$ I noticed a lack of test-cases. Didn't see anything in the comments about this so I wondered as his reference program ignores invalid commands while yours might execute them as valid commands if the sum of the character codes matches a valid command. \$\endgroup\$
– Emigna
May 8, 2017 at 12:22

Add a comment |

Leaky Nun · Accepted Answer · 2017-05-06 15:25:55Z

2

Pyth, 69 bytes

Vczd=Y.v@c"+YsY X_1Y1 +Yw  +Y0 X_1Y_1    PY   +Y1 tY +PYCeY"d%CN23;eY

Try it online!

edited May 6, 2017 at 15:25

answered May 6, 2017 at 15:10

Leaky Nun

49.6k6 gold badges107 silver badges281 bronze badges

\$\begingroup\$ Doesn't seem to work on the "Hello, World" program. \$\endgroup\$
– Okx
May 8, 2017 at 8:12
\$\begingroup\$ @Okx It does work; I changed the program in my link; the original program is too long. \$\endgroup\$
– Leaky Nun
May 8, 2017 at 8:12
\$\begingroup\$ Or a bunch of other programs, for that matter. 013456789yes 012345678no oh prints 0, expected output is 10. \$\endgroup\$
– Okx
May 8, 2017 at 8:15
\$\begingroup\$ Also doesn't work for the edge case yes yes oh (specified in the question), expected output is 11. \$\endgroup\$
– Okx
May 8, 2017 at 9:10
\$\begingroup\$ @Okx Look at the comments. The OP specifically specified this as undefined behaviour. \$\endgroup\$
– Leaky Nun
May 8, 2017 at 9:11

| Show 1 more comment

score 1 · Accepted Answer · 2017-05-06 13:02:43Z

JS (ES6), 361 340 bytes

c=>i=>(s=[],r="s[s.length-1]",c.replace(/[^a-z ]/g,"").split` `.map(x=>(eval({"yes":"s.push(1)","no":"s.push(0)","what":"s.push(i)","sure":"~++","nah":"~--","really":"~=((typeof ~)[0]<'o'?String.fromCharCode(~):lastItem.charCodeAt())","oh":"s.push(s.reduce((x,y)=>''+x+y))","nope":"s.shift()","yep":"s.pop()"}[x].replace(/~/g,r)))),eval(r))

Takes code and input through currying.

var yes = 
c=>i=>(s=[],r="s[s.length-1]",c.replace(/[^a-z ]/g,"").split` `.map(x=>(eval({"yes":"s.push(1)","no":"s.push(0)","what":"s.push(i)","sure":"~++","nah":"~--","really":"~=((typeof ~)[0]<'o'?String.fromCharCode(~):lastItem.charCodeAt())","oh":"s.push(s.reduce((x,y)=>''+x+y))","nope":"s.shift()","yep":"s.pop()"}[x].replace(/~/g,r)))),eval(r))

textarea{
  display: block;
}

Code: <textarea id = "code"></textarea>
Input: <textarea id = "input"></textarea>
<button onclick = "output.value = yes(code.value)(input.value)">Run</button>
<textarea id = "output"></textarea>

ETHproductions · Accepted Answer · 2017-05-06 15:55:52Z

0

JavaScript (ES6), 220 216 bytes

c=>i=>c.replace(/\w+/g,x=>a=a.concat(eval("Q,[]  (b=Q)[0]?b.charCodeAt():String.fromCharCode(b) 1    [a.join``,a=[]][0] Q+1 a.shift(),[]  i  Q-1".split`Q`.join`a.pop()`.split` `[parseInt(x,36)%19]||0)),a=[])&&a.pop()

A function that takes input with currying syntax, like f(code)(input).

edited May 6, 2017 at 15:55

answered May 6, 2017 at 15:44

ETHproductions

49.9k6 gold badges93 silver badges239 bronze badges

Add a comment |

ovs · Accepted Answer · 2017-05-06 16:57:39Z

0

Python 2, 258 bytes

s=[]
m=-1
i,p=input()
for c in p.split(' '):
 k=c<"o"
 if c in"yesnowhat":s+=[i if"w"==c[0]else-k+1]
 if c in"surenah":s[m]+=[1,m][k]
 if"p"in c:s.pop(k-1)
 if"oh"==c:s+=[''.join(map(str,s))]
 if"y"==c[m]:s[m]="'"in`s[m]`and ord(s[m])or chr(s[m])
print(s[m])

Try it online!

-3 bytes thanks to @Wondercricket

edited May 6, 2017 at 16:57

answered May 6, 2017 at 15:48

ovs

58.4k3 gold badges42 silver badges156 bronze badges

1

\$\begingroup\$ You can save 4 bytes by storing -1 as a variable \$\endgroup\$
– Wondercricket
May 6, 2017 at 16:23

Add a comment |

Brad Gilbert b2gills · Accepted Answer · 2017-05-06 17:13:30Z

Perl 6, 233 225 bytes

{my @s;{yes=>{@s.push(1)},no=>{@s.push(0)},what=>{@s.push: once slurp},sure=>{[email protected]},nah=>{[email protected]},really=>{($/:[email protected])~~Int??$/.=chr!!$/.=ord},oh=>{@s.=join},nope=>{@s.shift},yep=>{@s.pop},}{.words}.map:{.()};@s.tail.print}

Try it
Hello World
cat
-1
nul
cat_
0
1

{my @s;{es=>{@s.push(1)},no=>{@s.push(0)},at=>{@s.push: once slurp},re=>{[email protected]},ah=>{[email protected]},ly=>->{($_:[email protected])~~Int??.=chr!!.=ord},oh=>{@s.=join},pe=>{@s.shift},ep=>{@s.pop},}{.comb(/..»/)}.map:{.()};@s.tail.print}

Works the same except it only grabs the last two characters from each command, and uses $_ instead of $/ for really.

Try it (Hello World)

Expanded:

{
  my @s; # stack

  {  # Associative array
    yes    => {@s.push(1)},
    no     => {@s.push(0)},
    what   => {@s.push: once slurp}, # read everything from $*IN
    sure   => {[email protected]},
    nah    => {[email protected]},
    really => {
          ( $/ := @s.tail ) # bind $/ to the last value in the stack
          ~~ Int            # if that is an Int
      ??  $/.=chr           # replace it with that character
      !!  $/.=ord           # otherwise replace it with its ordinal
    },
    oh     => {@s.=join},
    nope   => {@s.shift},
    yep    => {@s.pop},
  }\
  { .words }                # index by the words in the program
  .map: {.()};              # call each of the lambdas in order

  @s.tail.print             # print the last value on the stack
}

Community · Accepted Answer · 2020-06-17 09:04:33Z

PHP, 315 305 bytes

second draft, not tested yet

foreach($argv as$k=>$v)if($k>1)eval((strstr($c=preg_replace('#[^a-z ]#','',$v),p)?'':'$s[]=').[yes=>1,no=>0,what=>'$argv[1]',sure=>'array_pop($s)+1',nah:'array_pop($s)-1',really=>'is_int($x=array_pop($s))?chr($x):ord($x)',oh=>'join($s)',nope=>'array_shift($s)',yep=>'array_pop($s)'][$c].';');echo end($s);

Run with php -nr '<php-code>' <input> <yes-code>.

breakdown

foreach($argv as$k=>$v)if($k>1)         # loop through commands
    eval(                                   # 3. interprete
        (strstr(                            # 2. if no 'p' in command, prepend '$s[]='
                                            # 1. ignore all non-code characters
            $c=preg_replace('#[^a-z ]#','',$v),p)?'':'$s[]=').
        [yes=>1,                                # yes: append 1
        no=>0,                                  # no: append 0
        what=>'$argv[1]',                       # what: append input
        sure=>'array_pop($s)+1',                # sure: remove end, increment, append
        nah:'array_pop($s)-1',                  # nah: remove end, decrement, append
                                                # really: convert between ascii and ordinal
        really=>'is_int($x=array_pop($s))?chr($x):ord($x)',
        oh=>'join($s)',                         # oh: concatenate elements, append
        nope=>'array_shift($s)',                # nope: remove first element
        yep=>'array_pop($s)']                   # yep: remove last element
        [$c]
    .';');
echo end($s);                           # print last element (if exists)

Wasif · Accepted Answer · 2021-03-24 17:40:28Z

PowerShell, 286 bytes

$s=@()
$k-split"\s"|%{
switch($_){
"yes"{$s+=1}
"no"{$s+=0}
"what"{$s+=(read-host)}
"sure"{$s[-1]+=1}
"nah"{$s[-1]-=1}
"really"{if($s[-1]-is[int]){[char]($s[-1])}else{[int][char]($s[-1])}}
"oh"{$s+=($s-join'')}
"nope"{$s=($s[1..($s.Length-1)])}
"yep"{$s=($s[0..($s.Length-2)])}}}
$s[-1]

Try it online!

The input is defined as $k in header of TIO.

An empty array $s initialized.

Splits the input on whitespace using a regex.

Then for each switch it does

yes: Push 1 to the stack (read stack as array and push as append, += operator used, which adds an item at the end of arrays (here))
no: Push 0 to the stack
what: Push the input to the stack
sure: Increment the last item in the stack (indexing and += used)
nah: Decrement the last item in the stack
really: If the last stack item is a number, replace it with its Unicode character. If it is a letter, replace it with its Unicode char code. (used [char] and [int][char] type casting)
oh: convert the stack to strings and concatenate it, and push that to the stack. (Just join the array with '')
nope: remove the first stack item (Using indexing)
yep: remove the last stack item (Using indexing)

At last output last item in array.

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Make an interpreter for yes!

Edge cases

10 Answers 10

JavaScript (ES6), 218 215 204 203 bytes

How?

Test cases

Röda, 256 bytes

Explanation

05AB1E, 77 67 63 61 bytes

Pyth, 69 bytes

JS (ES6), 361 340 bytes

JavaScript (ES6), 220 216 bytes

Python 2, 258 bytes

Perl 6, 233 225 bytes

Expanded:

PHP, 315 305 bytes

PowerShell, 286 bytes

Your Answer

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Make an interpreter for yes!

Edge cases

10 Answers 10

JavaScript (ES6), 218 215 204 203 bytes

How?

Test cases

Röda, 256 bytes

Explanation

05AB1E, 77 67 63 61 bytes

Pyth, 69 bytes

JS (ES6), 361 340 bytes

JavaScript (ES6), 220 216 bytes

Python 2, 258 bytes

Perl 6, 233 225 bytes

Expanded:

PHP, 315 305 bytes

PowerShell, 286 bytes

Your Answer

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