Define $\LaTeX$ Commands

1. \ifthenelse{\lengthtest{ \ft pt > 0 pt}}
{
   \tikzmath{\ft=1/sqrt(\ft);}
   \coordinate (t) at ($\ft*(i)+\ft*(p)$);
}{}
   %else statements
}
   
2. \IfFileExists{Curves/01.tex}
{
   \input{Curves/01.tex}
}{
   Nonexistent
}
   
3. \newcommand{safeinput}[1]
{
   \IfFileExists{#1}
   \input{#1}
}{
   #1: Nonexistent
}