Read arithmetic operator in postfix notation with scanf

Question

I am working on postfix calculator to read ~~operators~~ arithmetic operators. An example input is 24 5 6 * +.

This code read * and / operators but not read + and - operators:

while(scanf("%d",&temp))
    ARRAY[i]=temp;
scanf("%s",&operator);

What if `scanf` fails and returns `-1` ? this will still be true and you will save some garbage in temp. — Tony Tannous, Feb 16 '17 at 18:18
Possible duplicate of [C - Reading arithmetic operators with sscanf](http://stackoverflow.com/questions/17246910/c-reading-arithmetic-operators-with-sscanf) — Ishvar Patel, Feb 16 '17 at 18:18
`scanf("%c",&operator);` if `operator` is defined as a plain `char` — David Ranieri, Feb 16 '17 at 18:18
what is an `operator`? Is it a character array? If yes then omit `&` from second `scanf` — rootkea, Feb 16 '17 at 18:21
Even `scanf(" %c",&operator);` with a space to ensure the previous `newline` is ignored. — Weather Vane, Feb 16 '17 at 18:25

score 1 · Answer 1 · answered Feb 16 '17 at 18:43

The + and - characters could be the beginning of a number like "+3" or "-1". So code that is looking for a number will consume those characters. Don't use code to read a number unless you are certain you want to read a number and anything that's not a number is an error.

Read arithmetic operator in postfix notation with scanf

1 Answers1