Execute Brain****/Icon

From Rosetta Code
Execute Brain****/Icon is an implementation of Brainf***. Other implementations of Brainf***.
Execute Brain****/Icon is part of RCBF. You may find other members of RCBF at Category:RCBF.

This version of BF takes program and input from the parameter list. Memory grows as needed from a single cell. If no program is specified, the hello world program is run.

BF programtext inputtext
#
# bf interpreter
#
procedure main(arglist)
 
prog := get(arglist)
 
# test for nested brackets, previous version was deemed incorrect
if \prog == "hello" then
prog := ">++++++++[<+++++++++>-]<.>>+>+>++>[-]+<[>[->+<<++++>" ||
"]<<]>.+++++++..+++.>>+++++++.<<<[[-]<[-]>]<+++++++++" ||
"++++++.>>.+++.------.--------.>>+.>++++."
 
# default program
/prog := "++++++++++[>+>+++>++++>+++++++>++++++++>+++++++++>++" ||
"++++++++>+++++++++++>++++++++++++<<<<<<<<<-]>>>>+.>>>" ||
">+..<.<++++++++.>>>+.<<+.<<<<++++.<++.>>>+++++++.>>>.+++." ||
"<+++++++.--------.<<<<<+.<+++.---."
 
input := get(arglist)
/input := ""
 
# 1. toss obvious errors
 
b := 0
prog ? while i := move(1) do {
case i of {
"[" : b +:= 1
"]" : b -:= 1
}
if b < 0 then stop("malformed program, unbalanced []")
}
if b > 0 then stop("malformed program, unbalanced []")
 
write("Program is well formed.")
write("Program=",image(prog))
write("Ruler =",image(repl("0123456789",
*image(prog)/10 + 1)[1:*image(prog)-1]))
 
# 2. execute
 
cell := 1
mem := [0]
nest := 0
 
prog ? while i := move(1) do {
 
case i of {
 
# increment the pointer (to point to the next cell to the right)
">" :
if ( cell +:= 1 ) > *mem then
put(mem, 0)
 
# decrement the pointer (to point to the next cell to the left)
"<" :
if ( cell -:= 1 ) < 1 then
runerr(205,cell)
 
# increment (increase by one) the byte at the pointer.
"+" : mem[cell] +:= 1
 
# decrement (decrease by one) the byte at the pointer.
"-" : mem[cell] -:= 1
 
# output the value of the byte at the pointer.
"." : writes(char(mem[cell]))
 
# accept one byte of input, storing its value in the byte at the pointer.
"," : input ?:= ( mem[cell] := move(1), tab(0) )
 
# jump forward to the command after the corresponding ]
# if the byte at the pointer is zero.
"[" : if mem[cell] = 0 then {
repeat {
i := move(1)
if i == "[" then nest +:= 1 & next
if i == "]" then if nest = 0 then break else nest -:= 1
}
}
 
# jump back to the command after the corresponding [
# if the byte at the pointer is nonzero.
"]" : if mem[cell] ~= 0 then {
move(-1)
repeat {
i := move(-1)
if i == "]" then nest +:= 1 & next
if i == "[" then if nest = 0 then break else nest -:= 1
}
move(1)
}
}
# everything else is ignored/comment
}
end

Sample output:

#BF 
Program is well formed.
Program="++++++++++[>+>+++>++++>+++++++>++++++++>+++++++++>++++++++++>+++++++++++>++++++++++++<<<<<<<<<-]>>>>+.>>>>+..<.<++++++++.>>>+.<<+.<<<<++++.<++.>>>+++++++.>>>.+++.<+++++++.--------.<<<<<+.<+++.---."
Ruler  ="0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345"
Goodbye, World!

#BF hello
Program is well formed.
Program=">++++++++[<+++++++++>-]<.>>+>+>++>[-]+<[>[->+<<++++>]<<]>.+++++++..+++.>>+++++++.<<<[[-]<[-]>]<+++++++++++++++.>>.+++.------.--------.>>+.>++++."
Ruler  ="012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123"
Hello World!