BASIC-16A

* NAME: BASIC-16A DOC 70181826000 REV A PAGE 60

2179 * EXPRESSION ANALYZER 2180 * 2181 * 2182 * CALLING SEQUENCE: 2183 * 2184 * LDA PTRG A CONTAINS PRECEDENCE TRIGGER...SEE BELOW 2185 * JST EXPA 2186 * ......RETURN RESULT IN CVAL 2187 * 2188 * THIS ROUTINE WILL EVALUATE THE EXPRESSION IN THE 2189 * SOURCE STREAM UNIIL AN OPERATOR OF THE SAME 2190 * OR LOWER PRECEDENCE LEVEL AS INDICATED BY THE 2191 * INITIAL A REGISTER CONTENTS AS ENCOUNTERED. 2192 * THE FOLLOWING ARE THE DEFINED PRECEDENCE LEVELS: 2193 * 0 - DELIMITERS <EXPRESSION> 2194 * 1 - +,- <MULTIPLY FACTOR> 2195 * 2 - *,/ <INVOLUTION FACTOR> 2196 * 3 - ^ <TERM> 2197 * TO EVALUATE A COMPLETE EXPRESSION, THE INITIAL 2198 * A REGISTER VALUE WOULD BE 0. THE OTHER POSSIBLE 2199 * VALUES ARE USED PRIMARILY IN RECURSIVE CALLS TO 2200 * THIS ROUTINE MADE WITHIN IT. THE RESLUT OF THE 2201 * EXPRESSION IS LEFT IN THE FLOATING POINT ACCUMULTOR, 2202 * CVAL. THE PREVIOUS CONTENTS OF CVAL ARE LEFT 2203 * IN LVAL AND THE A + B REGISTERS ON RETURN. 2204 * 2205 * 2206 * EXPRESSION SYNTAX: 2207 * 2208 * <EXPRESSION>:=<MULTIPLY FACTOR>|<SIGN><EXPRESSION>| 2209 * <EXPRESSION>[+|-]<INVOLUTION FACTOR> 2210 * 2211 * <MULTIPLY FACTOR>:=<INVOLUTION FACTOR>|<MULTIPLY FACTOR> 2212 * [*|/]<INVOLUTION FACTOR> 2213 * 2214 * <INVOLUTION FACTOR>:=<TERM>|<INVOLUTION FACTOR>[^]<TERM> 2215 * 2216 * <TERM>:=<NUMBER>|<VARIABLE>|<FUNCTION TERM>|(<EXPRESSION>) 2217 * 2218 * <FUNCTION TERM>:=<FUNCTION NAME>(<EXPRESSION>) 2219 * 2220 * <FUNCTION NAME>:=SIN|COS|TAN|ATN|EXP|ABS|LOG|SQR|INT|RND| 2221 * SGN|FN<ALPHABETIC CHARACTER> 2222 * 2223 * <VARIABLE>:=<SIMPLE VARIABLE>|<SUBSCRIPTED VARIABLE> 2224 * 2225 * 2226 * 2227 * 2228 02443 0 000000 EXPA DAC **