PLC Laboratory 2

Lexical analyzer

Write a program, that reads an input and converts it into a sequence of lexical symbols – tokens. Each token composes from a type and possibly a value.

The tokens definition depends on you, and it is considered a part of the solution.

Input specification

The input may be containing the following symbols:

• identifiers - consisting of a sequence of letters and numbers starting with a letter
• numbers - formed by a sequence of decimal digits
• operators - symbols '+', '-', '*' and '/',
• delimiters - symbols '(', ')' and ';',
• keywords - div and mod.

Symbols can be separated by a sequence of spaces, tabs, and line breaks.

Notes are preceded by a sequence // and continue to the end of the line.

Output specification

For each expression write one line containing the result – the computed value of the expression. If there is any error in the input, write text ERROR instead.

Example

• Input

2
2 * (3+5)
15 - 2**7

• Output

16
ERROR