The objective of the present invention is the efficient analyzation of the structure of an array. By performing the prev(S) calculation for a character string S, if in S, a like variable is present upstream of a second variable, the second variable is changed to a numerical value that indicates the distance to the upstream like variable. But if in S, a like variable is not present upstream of a variable, that variable is changed to "0" to obtain a character string S1. Further, by performing the compl(S) calculation for S, if in the character string S a complementary variable is present upstream of a second variable, the second variable is changed to a numerical value that indicates the distance to the complementary variable. But if in S, a complementary variable is not present upstream of a variable, that variable is changed to "0" to obtain a character string S2.