05AB1E, 16(削除) 16 (削除ここまで) 14 bytes
×ばつs.×ばつS»X»D»Xr»×ばつ`»D®»
Explanation
×ばつ # create a string of the correct nr of horizontal chars
s.ø # add the corner char on both sides
U© # storesave in Xregister while keeping it on the stack
×ばつ|` # createpush athe stringremaining inputs to the top of the stack
×ばつ` # push the correct nr of vertical chars on the stack
S» » # split into list and # join on newline creating(joining athe top vertical string
and horizontal sections)
X» D # join horizontal part and# verticalduplicate partthis
on newline
® D» # duplicatepush andthe joinhorizontal onpart newlineagain
Xr» » # join a last horizontal# stringjoin ineverything theon beginningnewline
Saved 24 bytes thanks to Adnan.
05AB1E, 16 bytes
×ばつs.×ばつS»X»D»Xr»
Explanation
×ばつ # create a string of the correct nr of horizontal chars
s.ø # add the corner char on both sides
U # store in X
×ばつ # create a string of the correct nr of vertical chars S» # split into list and join on newline creating a vertical string
X» # join horizontal part and vertical part on newline
D» # duplicate and join on newline
Xr» # join a last horizontal string in the beginning
Saved 2 bytes thanks to Adnan.
05AB1E, (削除) 16 (削除ここまで) 14 bytes
×ばつs.×ばつ`»D®»
Explanation
×ばつ # create a string of the correct nr of horizontal chars
s.ø # add the corner char on both sides
© # save in register while keeping it on the stack
|` # push the remaining inputs to the top of the stack
×ばつ` # push the correct nr of vertical chars on the stack
» # join on newline (joining the top vertical and horizontal sections)
D # duplicate this
® # push the horizontal part again
» # join everything on newline
Saved 4 bytes thanks to Adnan.
05AB1E, (削除) 16 (削除ここまで) 1716 bytes
×ばつS»X»D»Xr»×ばつs×ばつS»X»D»Xr»
Explanation
×ばつ # create a string of the correct nr of horizontal chars
«R3«s.ø # add the corner char on both sides
U # store in X
×ばつ # create a string of the correct nr of vertical chars
S» # split into list and join on newline creating a vertical string
X» # join horizontal part and vertical part on newline
D» # duplicate and join on newline
Xr» # join a last horizontal string in the beginning
Saved 1 byte2 bytes thanks to Adnan.
05AB1E, (削除) 16 (削除ここまで) 17 bytes
×ばつS»X»D»Xr»
Explanation
×ばつ # create a string of the correct nr of horizontal chars
«R3« # add the corner char on both sides
U # store in X
×ばつ # create a string of the correct nr of vertical chars
S» # split into list and join on newline creating a vertical string
X» # join horizontal part and vertical part on newline
D» # duplicate and join on newline
Xr» # join a last horizontal string in the beginning
Saved 1 byte thanks to Adnan.
05AB1E, 16 bytes
×ばつs×ばつS»X»D»Xr»
Explanation
×ばつ # create a string of the correct nr of horizontal chars
s.ø # add the corner char on both sides
U # store in X
×ばつ # create a string of the correct nr of vertical chars
S» # split into list and join on newline creating a vertical string
X» # join horizontal part and vertical part on newline
D» # duplicate and join on newline
Xr» # join a last horizontal string in the beginning
Saved 2 bytes thanks to Adnan.
05AB1E, 16(削除) 16 (削除ここまで) 17 bytes
×ばつS»X»D»Xr»×ばつS»X»D»Xr»
Explanation
×ばつ×ばつ # create a string of the correct nr of horizontal chars
«R3« # add the corner char on both sides
U # store in X
×ばつ # create a string of the correct nr of vertical chars
S» # split into list and join on newline creating a vertical string
X» # join horizontal part and vertical part on newline
D» # duplicate and join on newline
Xr» # join a last horizontal string in the beginning
Saved 1 byte thanks to Adnan.
05AB1E, 16 bytes
×ばつS»X»D»Xr»
Explanation
×ばつ # create a string of the correct nr of horizontal chars
«R3« # add the corner char on both sides
U # store in X
×ばつ # create a string of the correct nr of vertical chars
S» # split into list and join on newline creating a vertical string
X» # join horizontal part and vertical part on newline
D» # duplicate and join on newline
Xr» # join a last horizontal string in the beginning
Saved 1 byte thanks to Adnan.
05AB1E, (削除) 16 (削除ここまで) 17 bytes
×ばつS»X»D»Xr»
Explanation
×ばつ # create a string of the correct nr of horizontal chars
«R3« # add the corner char on both sides
U # store in X
×ばつ # create a string of the correct nr of vertical chars
S» # split into list and join on newline creating a vertical string
X» # join horizontal part and vertical part on newline
D» # duplicate and join on newline
Xr» # join a last horizontal string in the beginning
Saved 1 byte thanks to Adnan.