Bash expansion repeat a string n to n times

Question

I'm trying to find combinations of characters that fit a (c)v pattern for up to n syllables, and so started by using expansion like echo {,p,t}{a,i} for all the possibilities for one syllable (using just 2 letters for readability). In order to get more syllables, all I could think of was expanding it for each syllable like echo {{,p,t}{a,i},{,p,t}{a,i}{,p,t}{a,i}} (ie, 'all the one syllable combinations then all the two syllable combinations'). Is there a better way to extend this to n syllables, so that I can type something kinda like echo {,p,t}{a,i}*{1..3} for all the 1, 2, and 3 syllable expansions(and so on)?

Answer 1

You could do something like this

Bash, 165 bytes

f(){
i=$1
exp=$2
con=$2
printf '{'
while [ "$i" -gt 0 ] ; do
  (( i-- ))
  printf '%s' "$con,"
  con+=$exp
done
printf '}'
echo
}

eval echo "$(f 6 '{,p,t}{a,i}')"

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Answer 2

Zsh, 73 bytes

c=('' p t) v=(a i) r=({1..4})
(){echo ${(e)@}} '${(el['$^r'*6][$^c$^v])}'

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Unrolling it:

$ c=( '' p t ) v=( a i ) r=( {1..4} )
$ echo $c$v
p ta i
$ echo $^c$^v
a i pa pi ta ti

With $^c instead of $c, arrays are expanded a bit like in brace expansion.

$ echo ${(l[12][$^c$^v])}
$^c$^v$^c$^v

We expand nothing (that parameter expansion has no parameter) using the left padding operator, here padding with $^c$^v strings to a length of 12 (twice the length of $^c$^v string).

$ echo ${(el[12][$^c$^v])}
aa ai apa api ata ati ia ii ipa ipi ita iti paa pai papa papi pata pati pia pii pipa pipi pita piti taa tai tapa tapi tata tati tia tii tipa tipi tita titi

If we add the e parameter expansion flag, the expansions in the result are evaluated/expanded.

So all we need to do is generate those for paddings of 6, 12, ... n*6.

$ echo '${(el['$^r'*6][$^c$^v])}'
${(el[1*6][$^c$^v])} ${(el[2*6][$^c$^v])} ${(el[3*6][$^c$^v])} ${(el[4*6][$^c$^v])}

If we can put those words in an array, we can apply the e flag to it to expand the result. For that we use an anonymous function, and pass those words as arguments, and they'll be available in the $@ aka $argv array within.

Answer 3

Usind the most of your code/logic.

ksh, 95 bytes, no evil eval :)

n=4
for ((i=1; i<=n; i++)) {
    printf -v x '{,p,t}{a,i}%.0s' {1..$i}
    printf '%s\n' $x
}

If your ksh implementation don't support printf -v x, replace by x=$(printf ...)

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