3.1 Example 1

Let us consider the following grammar for an integer. Let us define Σ = {0,1,2,3,4,5,6,7,8,9,+,-}, N = {S,D,I,J}. Let S be the start symbol.

• S ::= JI
• J ::=
• J ::= "+"
• J ::= "-"
• D ::= "0"
• D ::= "1"
• D ::= "2"
• D ::= "3"
• D ::= "4"
• D ::= "5"
• D ::= "6"
• D ::= "7"
• D ::= "8"
• D ::= "9"
• I ::= D
• I ::= ID

Let us see how this works. Our first string is -562.

• J ::= "-": the minus symbol is now J.
• D ::= "5": the first digit is now D.
• I ::= D: the first digit is now I.
• D ::= "6": the second digit is now D.
• I ::= ID: the first and second digits are now I.
• D ::= "7": the last digit is now D.
• I ::= ID: all digits are now I.
• S ::= JI: the sign and all digits are now S.