Execute Brain****: Difference between revisions
→{{header|UNIX Shell}}: Add implementation
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[[/Tcl|Implementation in Tcl]].
=={{header|UNIX Shell}}==
{{works with|Bourne Again SHell}}
<lang bash>#!/usr/bin/env bash
# BrainF*** interpreter in bash
if (( ! $# )); then
printf >&2 'Usage: %s program-file\n' "$0"
exit 1
fi
# load the program
exec 3<"$1"
program=()
while IFS= read -r line <&3; do
mapfile -t instr < <(tr -cd '[]<>.,+-' <<<"$line" | sed $'s/./&\\\n/g')
program+=("${instr[@]}")
done
exec 3<&-
# parse loops
loops=()
matches=()
for pc in "${!program[@]}"; do
instr=${program[pc]}
if [[ $instr == '[' ]]; then
loops=("$pc" "${loops[@]}")
elif [[ $instr == ']' ]]; then
matches[$pc]=${loops[0]}
matches[${loops[0]}]=$pc
loops=(${loops[@]:1})
fi
done
# execute program
memory=(0)
mp=0
pc=0
while (( pc < ${#program[@]} )); do
instr=${program[pc]}
(( pc+=1 ))
mem=${memory[mp]}
case "$instr" in
'[') if (( ! mem )); then (( pc=${matches[pc-1]}+1 )); fi;;
']') if (( mem )); then (( pc=${matches[pc-1]}+1 )); fi;;
+) memory[mp]=$(( (mem + 1) % 256 ));;
-) memory[mp]=$(( (mem - 1) % 256 ));;
'>') (( mp+=1 )); if (( mp >= ${#memory[@]} )); then memory+=(0); fi;;
'<') (( mp-=1 )); if (( mp < 0 )); then memory=(0 "${memory[@]}"); mp=0; fi;;
.) printf %b $(printf '\\%03o' "$mem");;
,) printf 'Raeding!\n' >&2; read -n1 c; memory[mp]=$(LC_CTYPE=C printf '%d' "'$c");;
esac
done</bash>
<pre>
Sample run:
{{Out}}
<pre>$ bash bf.bash <(echo '>++++++++[<+++++++++>-]<.>>+>+>++>[-]+<[>[->+<<++++>]<<]>.+++++++..+++.>>+++++++.<<<[[-]<[-]>]<+++++++++++++++.>>.+++.------.--------.>>+.>++++.')
Hello World!</pre>
=={{header|VBScript}}==
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