Are these identifiers equivalent?

Question

In the language Nim, the rules for differentiating identifiers are slightly more relaxed than most other languages. Two identifiers are equivalent or address the same variable if they follow these rules:

• the first character of both are the same (case sensitive)
• both strings are the same (case insensitive) after removing all instances of the characters - and _

Challenge

Write a program/function that takes two strings that represent Nim identifiers and output a truthy or falsey value based on whether or not they are equivalent by the rules above.

Specifications

• Standard I/O rules apply.
• Standard loopholes are forbidden.
• The strings will only contain ASCII printables. You do not need to check if it's a valid identifier.
• The strings may be taken as two separate inputs, list of strings, etc. (you know the drill)
• Empty strings need not be handled.
• The output must be consistent for both truthy and falsey values.
• This challenge is not about finding the shortest approach in all languages, rather, it is about finding the shortest approach in each language.
• Your code will be scored in bytes, usually in the encoding UTF-8, unless specified otherwise.
• Built-in functions that perform this task are allowed but including a solution that doesn't rely on a built-in is encouraged.
• Explanations, even for "practical" languages, are encouraged.

Test cases

Input                                    Output

count, Count                             falsey
lookMaNoSeparator, answer                falsey
_test, test                              falsey
test, tset                               falsey
aVariableName, a_variable_name           truthy
numbers_are_cool123, numbersAreCool123   truthy
symbolsAre_too>_>, symbols_areTOO>>      truthy

Ungolfed reference implementation

This is written in Nim, itself.

import strutils, re

proc sameIdentifier(a, b: string): bool =
  a[0] == b[0] and
    a.replace(re"_|–", "").toLower == b.replace(re"_|–", "").toLower

Answer 1

JavaScript (ES6), 62 61 bytes

Saved 1 byte thanks to @JohanKarlsson

Takes input in currying syntax (a)(b). Returns a boolean.

a=>b=>(r=s=>s[0]+s.replace(/-|_/g,'').toUpperCase())(b)==r(a)

Test cases

let f =

a=>b=>(r=s=>s[0]+s.replace(/-|_/g,'').toUpperCase())(b)==r(a)

console.log(f("count")("Count"))                           // falsey
console.log(f("lookMaNoSeparator")("answer"))              // falsey
console.log(f("_test")("test"))                            // falsey
console.log(f("aVariableName")("a_variable_name"))         // truthy
console.log(f("numbers_are_cool123")("numbersAreCool123")) // truthy

Answer 2

Python 3, 76 bytes

lambda a,b:f(*a)==f(*b)
f=lambda f,*r:[f+k.lower()for k in r if~-(k in'-_')]

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-1 byte thanks to notjagan
-3 bytes thanks to Wheat Wizard

Answer 3

Actually, 15 bytes

⌠p"-_"(-Σùo⌡M═Y

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Fun fact: this works with any number of inputs (it always returns truthy for less than 2 inputs).

Explanation:

⌠p"-_"(-Σùo⌡M═Y
⌠p"-_"(-Σùo⌡M    for each input:
 p                 separate the first character
  "-_"(-           remove all dashes and underscores from the rest of the string
        Σù         concatenate the list from the last operation and lowercase the string
          o        append it to the first character
             ═Y  are none of the elements unique?

Answer 4

Jelly, 11 bytes

ḟ⁾-_Œl,Ḣµ€E

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-2 bytes thanks to Erik the Outgolfer
-1 byte thanks to Jonathan Allan

Answer 5

Pyth, 13 bytes

qFm[hd-r0d"-_

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Explanation

qFm[hd-r0d"-_
  m              For each value in the input (which is a list of two strings):
   [             Create a list consisting of
    hd               the first character of each value
      -r0d"-_        and the lowercase version of the value without "-" or "_"
qF               Fold over equivalence; checks to see if both lists are the same

Answer 6

Ruby, 86 64 63 61 51 bytes

f=->x{x[0]+x.upcase.delete("-_")}
->x,y{f[x]==f[y]}

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This feels really long still feels a bit long. I would appreciate the help of any Ruby gurus out there in making this at least a bit shorter.

Answer 7

05AB1E, 12 bytes

εćs„-_SKl«}Ë

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-1 thanks to Adnan.

Theoretically, εćs„-_-«}Ë should've worked for 10 bytes, but unfortunately this behavior is deprecated for now.

Answer 8

C++, 288 248 bytes

-5 bytes thanks to Zacharý

#include<string>
#include<algorithm>
#define E(a,v)a.erase(std::remove(a.begin(),a.end(),v),a.end());
#define F(a)for(auto&c:a)c=toupper(c);
int e(std::string&a,std::string&b){if(a[0]!=b[0])return 0;E(a,45)E(b,45)E(a,95)E(b,95)F(a)F(b)return a==b;}

Thanks you, Preprocessor. Also, this code takes advantage of the fact that in C++ the rule to cast int to bool is int_var!=0

Answer 9

CJam, 20 bytes

{_"-_"f-:el:=\:c:=*}

Takes input in the form of ["string1","string2"].

Try it Online (testing version)

{
_      e# make copy of input
"-_"f- e# remove all "-" and "_" from both words in copy
:el    e# convert words in copy to lowercase
:=     e# 1 if both words in copy are equal, 0 if not
\      e# move original version of input to top of stack
:c     e# convert each word in original input to only 1st character
:=     e# 1 if both characters from original input are equal, 0 if not
*      e# multply the two numbers we obtained. If and only if both are 1 (true) we return 1 (true)
}

Answer 10

Haskell, 85 78 76 71 68 bytes

2 bytes saved thanks to Ørjan Johansen

import Data.Char
s(a:x)=a:[toLower a|a<-x,all(/=a)"-_"]
x!y=s x==s y

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Errors on the empty string.

Answer 11

Python 2, 72 bytes

lambda x,y:r(x)==r(y)
r=lambda x:x[0]+x[1:].lower().translate(None,"-_")

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Won't work with Python 3 because of the new translate syntax.

Answer 12

Excel, 105 bytes

=AND(CODE(A1)=CODE(B1),SUBSTITUTE(SUBSTITUTE(A1,"_",""),"-","")=SUBSTITUTE(SUBSTITUTE(B1,"_",""),"-",""))

CODE() returns numeric code of first character.

String comparison in Excel is case insensitive.

Answer 13

Husk, 13 bytes

¤=§,←(m_ω-"-_

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Builds for each string a pair consisting of the first character of the string and the whole string lowercased and with all occurrences of -/_ removed. Then checks if the two pairs are equal.

A particularity is that - in Husk is set difference (i.e. it removes only the first occurrence found): in order to remove all occurrences, the fixed point of -"-_ is found with ω-"-_.

Answer 14

Japt, 14 25 bytes

g ¥Vg ©Uu k"_-" ¥Vu k"_-"

Checks case-insensitive string equality by removing all characters in word 2 from word 1, and removing the -_ characters; that results in an empty string ("") if the words are equal.
Thanks Ørjan Johansen for pointing out the problem with this.

Checks first-char equality and if the uppercased inputs are equal after removing _-.

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Explanation

Implicit input: U and V are input strings

g ¥Vg

Check if first letter of U (implicit) equals (¥) the first char of V.

©Uu k"_-" ¥Vu k"_-"

And (©) check if U, uppercased (u) and with _- removed (k), equals (¥) the same for V. Implicitly return the boolean result.

Answer 15

Perl 5, 67 bytes

s/.//,push@a,$&,y/_-//dr for<>;say($a[0]eq$a[2]&&lc$a[3]eq lc$a[1])

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Takes the identifiers as input on separate lines.

Explanation:

s/.//,             # remove the first character
push@a,            # storage space, even positions are first character
                   # odd positions are remainder
$&,                # implicit variable holding last matched pattern (first char)
y/_-//dr           # Remove _ and - from remainder of input
for<>;             # iterate over all input lines
say                # output
($a[0]eq$a[2]&&    # check that first character is identical and
lc$a[3]eq lc$a[1]) # so is the lowercase version of the rest

Answer 16

Python 2, 79 73 bytes

-6 bytes thanks to @notjagan: check the length of set of all reduced names is 1 or not.

lambda*l:len({x[0]+re.sub('-|_','',x[1:].lower())for x in l})<2
import re

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Answer 17

Retina, 28 bytes

T`L\_-`l_`(?<=.).+
^(.*)¶\1$

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Answer 18

Charcoal, 29 bytes

∧⁼§θ⁰§η⁰⁼↧⪫⪪⪫⪪θ_ω-ω↧⪫⪪⪫⪪η_ω-ω

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This prints a - for truthy and nothing for falsey.

Link to the verbose version. It first compares the first character of both input strings (⁼§θ⁰§η⁰) and then compares the rest of both strings after removing the underscores and the hyphens (⪫⪪⪫⪪θ_ω-ω) and converting to lowercase (↧).

Answer 19

C#, 101 89 bytes

string g(string s)=>string.Concat(s.ToUpper().Split('-','_'));f=>s=>f[0]==s[0]&g(f)==g(s)

Saved 12 bytes thanks to @kusi581.

Answer 20

Java (OpenJDK 8), 95 bytes

a->b->a.charAt(0)==b.charAt(0)&&a.replaceAll("_|-","").equalsIgnoreCase(b.replaceAll("_|-",""))

Try it online! Pretty straight forward.

Answer 21

Pyke, 13 bytes

F'hl1"-_"-)Xq

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F         )   -  for i in input():
 'hl1         -   i[0], i.lower()
     "-_"-    -         ^.remove("-_")
           Xq - equal(^)

Answer 22

C (gcc), 126 114 bytes

#define p(s)do++s;while(*s==45||*s==95);*s>95?*s-=32:0;
f(char*a,char*b){while(*a&&*a==*b){p(a)p(b)}return*a==*b;}

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With whitespace and comments:

#define p(s)                   // Define helper macro p           \
    do ++s;                    // Increment pointer at least once \
    while (*s==45 | *s==95);   // and past any '-' or '_'         \
    *s>95 ? *s -= 32 : 0;      // If lowercase letter, convert to upper

f(char* a, char* b) {          // Define main function f
    while (*a && *a == *b) {   // Loop until end of either string
                               // or a difference found
        p(a)                   // Transform pointer and one char
        p(b)                   // via helper p above
    }
    return *a==*b;             // Test chars equal (on success, both '\0')
}

Answer 23

Dyalog APL, 47 32 28 27 26 22 bytes

-4 bytes thanks to Kritixi Lithos

{(=/⊃¨⍵)∧≡/819⌶⍵~'-_'}   

Takes input as a list of the strings.

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How?

{(=/⊃¨⍵)∧≡/819⌶⍵~'-_'}
               ⍵~'-_'   Remove '-' and '_'
           819⌶         Lowercase
         ≡/             Equality between elements
        ∧               And
 (=/⊃¨⍵)                The first element of each element is equal

Answer 24

Common Lisp, 98 bytes

(lambda(x y)(and(eql(elt x 0)(elt y 0))(string-equal(#1=remove #\-(#1##\_ y))(#1##\-(#1##\_ x)))))

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Ungolfed (super straightforward!) version:

(defun f(x y)
  (and (eql (elt x 0) (elt y 0))         ; check if initial characters are identical
       (string-equal                     ; string comparison (case insensitive)
         (remove #\- (remove #\_ y))     ; remove from both strings the unwanted chars
         (remove #\- (remove #\_ x)))))

Answer 25

R, 76 bytes

function(l)(g=substr(l,1,1))[1]==g[2]&(h=tolower(gsub('-|_','',l)))[1]==h[2]

Anonymous function that takes input as a list of two strings. Takes advantage of the fact that R's string operations, while quite long in # of characters, are vectorized. Additionally wrapping an assignment in parentheses will bind the variable, so (g=substr(l,1,1)) retains a variable to be reused later in the line and similarly for h.

R returns the last evaluated expression as function output.

Ungolfed:

function(l){
  g <- substr(l,1,1)
  h <- tolower(gsub("_|-","",l))
  (g[1]==g[2])&(h[1]==h[2])
}

Try it online! (all test cases)

Answer 26

Brachylog, 17 bytes

hᵛ&{{¬∈"_-"&ụ}ˢ}ᵛ

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Outputs through predicate success/failure.

h                    The first element
 ᵛ                   is the same for each element of the input,
  &                  and
   {           }ᵛ    for each element of the input the following are the same:
    {      &ụ}ˢ      every element uppercased which satisfies the condition that
     ¬∈              it is not an element of
       "_-"          the string "_-".

Answer 27

Erlang 113 bytes

A=fun(L)->string:to_lower(lists:flatten(string:tokens(L,"-_")))end,fun([C|D],[C|E])->A(D)==A(E);(_,_)->a==b end.

a pair of anonymous functions that compare the two lists. meant to be pasted in the erlang shell.

more readable:

A=fun(L) ->
    string:to_lower( % case insensitive
        lists:flatten( % squash all characters back into one list
            string:tokens(L,"-_") % return a list of list of characters
        )
    )
end.
fun([C|D],[C|E]) -> % are the first characters exactly the same?
    A(D)==A(E); % does the rest compare correctly?
   (_,_) -> % first chars not the same
    a==b % shorter than 'false'
end.

Answer 28

Clip, 25 bytes

&=(x(y=AxAy[Aa--m.L`a'-'_

Explanation:

x, y and z may be referenced in a Clip program to implicitly take up to three inputs. Since this program only references x and y, it takes two inputs which are assigned to x and y.

 =(x(y                    First characters of x and y are equal
&                         And
      =AxAy               A(x) == A(y)
           [Aa            Function A, takes parameter a
                m.L`a     Map all elements of a to lower case
              --     '-'_ Remove all occurrences of '-' and '_'

Takes two strings from standard input, outputs 1 and 0 for true and false respectively.