6.3.5  First character, middle and end of a string: head mid tail

The head command finds the first character of a string.

• head takes one argument:
  str, a string.
• head(str) returns the first character of the string str.

Example.
Input:

Output:

The mid command finds a selected part from the middle of a string.

• mid takes three arguments:
  • str, a string.
  • p, an integer for the starting index of the result.
  • q, an integer q for the length of the string.
• mid(str,p,q) returns the part of the string str starting with the character at index p with length q. (Remember that the first index is 0 in Xcas mode.)

Example.
Input:

Output:

The tail command removes the first character of a string.

• tail takes one argument:
  str, a string.
• tail(str) returns the string str without its first character.

Input:

Output: